EP3946779A1

EP3946779A1 - Systems and methods for injection molding of nanocrystalline metal powders

Info

Publication number: EP3946779A1
Application number: EP20721923.9A
Authority: EP
Inventors: Alan C. Lund; Troy Holland; Luke Eastman JORGENSEN
Original assignee: Veloxint Corp
Current assignee: Veloxint Corp
Priority date: 2019-03-28
Filing date: 2020-03-27
Publication date: 2022-02-09
Also published as: JP2022527477A; KR20220023823A; WO2020198658A1; CN115052696A

Abstract

Embodiments described herein relate generally to systems and methods for using nanocrystalline metal alloy particles or powders to create nanocrystalline and/or microcrystalline metal alloy articles using a nanocrystalline metal injection molding (NMIM) process. In some embodiments, a method for manufacturing a metal article using NMIM includes mixing a plurality of nanocrystalline metal particles with a binder to form a molding feedstock,, transferring the molding feedstock to a mold to form a molded structure, debinding the molded structure, and sintering the molded structure to form a metal alloy article, the metal alloy article having a relative density of at least about 90 %. In some embodiments, the molding feedstock can include less than about 55 vol% of the nanocrystalline metal particles.

Description

SYSTEMS AND METHODS FOR INJECTION MOLDING OF NANOCRYSTALLINE METAL POWDERS

Cross-reference to Related Applications

[0001] This application claims priority and benefit of U.S. Provisional Application No.

62/825,611, filed March 28, 2019 and entitled“Systems and Methods for Injection Molding of Nanocrystalline Metal Powders”, the entire disclosure of which is hereby incorporated by reference herein in its entirety.

Background

[0002] Embodiments described herein relate generally to systems and methods for injection molding of nanocrystalline metal alloy powders. When a nanocrystalline metal alloy molding compound is used, conventional methods for injection molding of metal particles often results in a compounded material that is oxidatively unstable and a sintered part having increased incidence of defects and unsatisfactory mechanical properties. Additionally, achieving high solids loading when using nanocrystalline metal particulates in a metal injection molding process can be quite difficult due to the high surface area of the nanocrystalline metal particulates.

Summary

[0003] Embodiments described herein relate generally to systems and methods for using nanocrystalline metal alloy particles or powders to create nanocrystalline and/or microcrystalline metal alloy articles using a nanocrystalline metal injection molding (NMIM) process. In some embodiments, a method for manufacturing a metal article using NMIM includes mixing a plurality of nanocrystalline metal particles with a binder to form a molding feedstock, transferring the molding feedstock to a mold to form a molded structure, debinding the molded structure, and sintering the molded structure to form a metal alloy article, the metal alloy article having a relative density of at least about 90 %. In some embodiments, the molding feedstock can include less than about 55 vol% of the nanocrystalline metal particles.

[0004] In some embodiments, the debinding can include thermal debinding, catalytic debinding, and/or chemical debinding. In some embodiments, the method can further include pressing the metal alloy article in a pressure vessel. In some embodiments, the molding feedstock can include less than about 52 vol% of the nanocrystalline metal particles. In some embodiments, the molding feedstock can include less than about between about 48 vol% and about 55 vol% of the nanocrystalline metal particles. In some embodiments, the metal alloy articles can have a relative density of at least about 95 %, at least about 98 %, or at least about 99 %. In some embodiments, the nanocrystalline metal particles can be mixed with a wetting agent, a lubricant, or other compounds that may assist with compounding during the NMIM process. In some embodiments, the ratio of the relative density to the weight fraction of the nanocrystalline metal particles is at least about 1.5:1, at least about 1.75: 1, at least about 1.8: 1, at least about 1.85: 1, or at least about 1.9: 1.

Brief Description of the Drawings

[0005] FIG. 1 shows a method 100 of producing a metal alloy article via injection molding of nanocrystalline metal powders.

Detailed Description

[0006] Embodiments described herein relate generally to systems and methods for using metal particles or powders to create metal alloy articles using a nanocrystalline metal injection molding (NMIM) process. In some embodiments, a method for manufacturing a metal article using NMIM includes mixing a plurality of metal particles with a binder to form a molding feedstock, transferring the molding feedstock to a mold to form a molded structure, debinding the molded structure, and sintering the molded structure to form a sintered article. In some embodiments, debinding includes at least one of thermal debinding, catalytic debinding, and chemical debinding. In some embodiments, the metal particles can be nanocrystalline.

[0007] Metal alloy articles produced from metal injection molding (MIM) via an injection device often have a density that is directly proportional to the weight percentage of metal particles in the molding feedstock (i.e., the solids loading of the molding feedstock). A commonly employed strategy for producing a metal alloy article with a high relative density includes effecting the solids loading of the molding feedstock to be as high as possible. However, the achievable level of solids loading can be constrained by the performance parameters of the injection device. Using metal particles or powders that include nanocrystalline metal particles or powders in a MIM process can create a metal alloy article with a high relative density from relatively low solids loading during production.

[0008] Conventional metallurgical methods include development of a finished metal article through precise removal of material from a sintered bulk metal material, the formation of sintered subcomponent parts that are later assembled into the metal part, or the mixing of metal powder with a binder and compounding into a green body for sintering of the green body. However, removal of material to form a complex part is highly time-consuming and expensive, the assembly of subcomponent parts into the complex part requires additional steps and produces a part that does not achieve desired mechanical properties, and green body formation of metal powders is typically only useful for simple parts that require a single compounding (pressing) step before sintering.

[0009] The conventional metal injection molding (MIM) process is a manufacturing process intended to produce a large quantity of often complex, often small metal articles. MIM combines the versatility and high productivity of plastics injection molding with powder metallurgy techniques such as mechanical alloying and sintering that produce a more durable metal finished article.

[0010] MIM processes have been developed recently that allow for more precise and more rapid production of complex metal articles. MIM processes include the mixing of a base metal powder and alloying elements, adding a polymer and/or a wax, and kneading the mixture to form a homogenous molding feedstock. The molding feedstock is then injected at elevated temperature and pressure into a cavity, for example a mold, to form a compounded green body. The compounded green body is then typically passed through a thermal debinding step, chemical debinding step, and/or catalytic debinding step to remove most or substantially all of the polymer and/or wax binder. Finally, the green body after debinding is sintered to form the finished article.

[0011] Some of the challenges faced during the MIM process include but are not limited to the handling of the molding feedstock (e.g., how to get make the metal powder flow into the mold), the reactivity of the molding feedstock material during kneading, passivation, and/or upon compounding of the molding feedstock into the mold, the formation of defects during chemical and/or thermal debinding of the MIM material compound, how to retain the shape of the molded article before sintering, and maintaining mechanical properties of the finished, sintered alloy above desired thresholds. [0012] Conventional MIM processes typically use metal particles having a coarse or ultrafme grain size, which results in a finished metal part having relatively poor mechanical properties. In addition, conventional metal particles having nanostructured or microstructured grains are often not as compoundable as nanocrystalline metal alloy particles produced according to the mechanical alloying processes described herein. Conventional nanocrystalline alloy powders are also nanoparticles (i.e., particles with an average particle dimension of less than 1,000 nm) and will often be more reactive due to a higher surface area/volume ratio, meaning more grain boundaries are exposed and more oxidation will occur during passivation. In addition, conventional nanocrystalline alloy powders may experience more grain growth after milling and during sintering, which may lead to fracturing of particles and a higher defect rate in the finished article. These factors may lead to increased defects, higher porosity, a higher rate of vacancies in the green body, and/or a lower gross particle density and packing density, which in turn can result in a less dense finished article with poor mechanical properties.

[0013] When conventional particles having fine or nanocrystalline grain size are used in the MIM process a higher mass ratio (e.g., 1.5: 1) of binder to metal particles is often used in order to maintain a flowable powder for the conventional MIM process. However, the higher proportion of binder in the molding feedstock can lead to a significant increase in defect rate after thermally and/or chemically debinding.

[0014] Additionally, because conventional nanocrystalline particles are also nanoparticles, when conventional metal particles having a fine or nanoscale grain size are used in the MIM processes, the increase in grain boundaries typically result in an increase in specific surface area, and a far more unsafe process due to reactivity during passivation and compounding. For instance, conventional MIM processes using conventional nanostructured metal powders can have a specific surface area of between about 100 and about 300 m²/g and the grain size and particle size can be substantially similar. Therefore, conventional nanostructured metal powders having such specific surface area to volume ratios can react violently when exposed to air, for example, during passivation, can result in a molding feedstock that is sparking and/or reactive, for example during injection molding or thermal debinding, and can lead to a highly unsafe manufacturing environment.

[0015] Therefore, there has been a long-felt need in the industry for a process by which metal alloy particles can be made flowable enough to be injected into a mold and a corresponding metal injection molding process for forming a molded structure for which debinding results in no or fewer defects. [0016] As used herein, the terms “about”, “approximately”, and “substantially” generally mean plus or minus 10% of the value stated, e.g., about 250 nm would include 225 nm to 275 nm, about 1,000 nm would include 900 nm to 1,100 nm.

[0017] As used herein, the term“hardness” refers to how resistant a material is to permanent shape change when a compressive force is applied.

[0018] As used herein, the term“ductility” refers to the ability of a material to deform plastically under tensile loading without fracturing or rupturing.

[0019] As used herein, the term“toughness” refers to the ability of a material to plastically deform without fracturing. Toughness can be thought of as a balance of hardness and ductility.

[0020] As used herein, the terms“nanostructured” and“nanocrystalline” refer to particle grain size dimensions less than about 100 nm.

[0021] As used herein, the term“ultra-fine” refers to particle grain size dimensions between about 100 nm and about 500 nm.

[0022] As used herein, the terms“microstructured” and“microcrystalline” refer to particle grain size dimensions greater than about 500 nm and less than about 5 pm.

[0023] As used herein, the term“coarse” refers to particle grain size dimensions greater than about 5 pm.

[0024] As used herein, the terms“green body,” or“molded structure,” refer to an obj ect whose main constituent is a weakly bound material, usually in the form of bonded powder before it has been sintered or fired. When using a binder, the term green body can similarly refer to a weakly bound binder network that can substantially form a metal and/or metal alloy material and a binder into a three-dimensional shape or object.

[0025] As used herein, the term“nanocrystalline” generally refers to a volume average grain size less than 1 pm, less than or equal to about 900 nm, about 800 nm, about 700 nm, about 600 nm, about 500 nm, about 400 nm, about 300 nm, about 200 nm, about 150 nm, about 100 nm, about 50 nm, about 30 nm, about 20 nm, about 10 nmor smaller.

[0026] Metal powders can be produced by mixing particles of one or more transition metals together and mechanically alloying the admixture until the grain size has been refined to the nanoscale. Examples of nanocrystalline metal alloy systems described herein are described in more detail in U.S. Patent Application Publication No. 2014/0271325 A1 (“the ‘325 publication”), entitled“Sintered Nanocrystalline Alloys”, filed March 14, 2014, U.S Provisional Patent Application No. 62/812,381 (“the ‘381 application”), entitled“Alloys Including A Ductilizing Agent and Methods of Making the Same”, filed February 26, 2018 , and U.S. Provisional Patent Application No. 62/812,383 (“the‘383 application), entitled “Chromium-Bearing Alloys Including A Toughening Agent and Methods of Making the Same”, filed February 26, 2018, the disclosures of which are hereby incorporated herein by reference in their entireties.

[0027] FIG. 1 shows a method 100 of producing a metal alloy article via injection molding of nanocrystalline metal powders. The method 100 optionally includes mechanical working of metal particles at step 102 and passivation of metal at step 104. The method 100 includes mixing binder and metal particles to form a molding feedstock at step 106. The method 100 can optionally include heating the molding feedstock at step 108 prior to transferring the molding feedstock to a mold to form a molded structure (or green body) at step 110. The molded structure is subject to debinding 112 and sintering 114 to form the metal alloy article. In some embodiments, the metal alloy article can be subject to densification at step 116. In some embodiments, debinding at step 112 and sintering at step 114 can be combined into a single step.

[0028] In some embodiments, the method 100 for making a plurality of nanocrystalline metal (NCM) alloy particulates can include mechanically working a powder including a plurality of metal particulates and a second metal material at step 102. In some embodiments, the first metal material can be a stabilizer element and the second metal material may be an activator element or a stabilizer element. In some embodiments, the method for making NCM alloy particulates can include mechanically working a powder including 3, 4, 5, 6, 7, 8, 9, 10, or more metal materials.

[0029] In some embodiments, the NCM powders can be formed from two or more metal materials, for instance one or more transition metals. Although referred to herein as the nanocrystalline alloy particles or NCM powders, microcrystalline alloy particles and ultrafme alloy particles can also be used. Examples of suitable alloy systems and methods of mechanically alloying and sintering are described in the ‘325 publication. In some embodiments, suitable alloy systems can include at least one of tungsten, osmium, rhenium, vanadium, iridium, tantalum, ruthenium, uranium, rhodium, niobium, germanium, chromium, manganese, titanium, hafnium, molybdenum, beryllium, zirconium, cobalt, palladium, nickel, iron, platinum, thorium, antimony, copper, and other metallic elements. [0030] The mechanical working may be a ball-milling process, a high-energy milling process, low-energy milling process, or the like. In some embodiments, the ball-milling process may employ a ball-to-powder ratio of about 2:1 to about 5:1 by weight, and a stearic acid process control agent content of about 0.01 wt. % to about 3 wt. %. In some embodiments, the mechanical working may be carried out in the presence of a steric acid process control agent content of about 1 wt. %, about 2 wt. %, or about 3 wt. %. In some embodiments, the mechanical working is carried out in the absence of a process control agent. In some embodiments, the ball milling may be performed under any conditions sufficient to produce a nanocrystalline particulate comprising a supersaturated phase.

[0031] In some embodiments, the ball-milling process can employ a ball-to-powder ratio of at least about 2:1, at least about 3:1, at least about 4:1, at least about 5:1, at least about 6:1, at least about 7:1, at least about 8:1, at least about 9:1, at least about 10:1, at least about 11:1, at least about 12:1, at least about 13:1, at least about 14:1, at least about 15:1, at least about 16:1, at least about 17:1, at least about 18:1, at least about 19:1. In some embodiments, the ball-milling process can employ a ball-to-powder ratio of no more than about 20: 1, no more than about 19:1, no more than about 18:1, no more than about 17:1, no more than about 16:1, no more than about 15:1, no more than about 14:1, no more than about 13:1, no more than about 12: 1, no more than about 11 : 1, no more than about 10: 1, no more than about 9: 1, no more than about 8:1, no more than about 7:1, no more than about 6:1, no more than about 5:1, no more than about 4: 1 , or no more than about 3:1. Combinations of the above-referenced ranges for ball-to-powder ratio are also possible (e.g., at least about 2:1 and no more than about 20:1 or at least about 3:1 and no more than about 5:1), inclusive of all values and ranges therebetween. In some embodiments, the ball-milling process can employ a ball-to-powder ratio of about 2:1, about 3:1, about 4:1, about 5:1, about 6:1, about 7:1, about 8:1, about 9:1, about 10:1, about 11:1, about 12:1, about 13:1, about 14:1, about 15:1, about 16:1, about 17:1, about 18:1, about 19:1, or about 20:1.

[0032] In some embodiments, the stearic acid process control agent content can be at least about 0.01 wt%, at least about 0.5 wt%, at least about 0.1 wt%, at least about 0.5 wt%, at least about 1 wt%, at least about 1.5 wt%, at least about 2 wt%, or at least about 2.5 wt%. In some embodiments, the stearic acid process control agent content can be no more than about 3 wt%, no more than about 2.5 wt%, no more than about 2 wt%, no more than about 1.5 wt%, no more than about 1 wt%, no more than about 0.5 wt%, no more than about 0.1 wt%, or no more than about 0.05 wt%. Combinations of the above-referenced stearic acid process control agent contents are also possible (e.g., at least about 0.01 wt% and no more than about 3 wt% or at least about 0.1 wt% and no more than about 0.5 wt%), inclusive of all values and ranges therebetween. In some embodiments, the stearic acid process control agent content can be about 0.01 wt%, about 0.05 wt%, about 0.1 wt%, about 0.5 wt%, about 1 wt%, about 1.5 wt%, about 2 wt%, about 2.5 wt%, or about 3 wt%.

[0033] In some embodiments, any appropriate method of milling may be employed to mechanically work a powder and form nanocrystalline particulates. In some embodiments, a ball mill may be employed. In some embodiments, a high-energy attritor mill may be employed. In some embodiments, other types of high-energy mills may be employed, including shaker mills and planetary mills. In general, any mechanical milling method that produces a mechanical alloying effect may be employed.

[0034] In some embodiments, milling may be conducted for a time of greater than or equal to about 2 hours - e.g., greater than or equal to about 4 hours, about 6 hours, about 8 hours, about 10 hours, about 12 hours, about 15 hours, about 20 hours, about 25 hours, about 30 hours, or about 35 hours. In some embodiments, ball milling may be conducted for a time of about 1 hour to about 35 hours - e.g., about 2 hours to about 30 hours, about 4 hours to about 25 hours, about 6 hours to about 20 hours, about 8 hours to about 15 hours, or about 10 hours to about 12 hours. If the milling time is too long, the powder may be contaminated by the milling vial material. The amount of the second metal material that is dissolved in the first metal material may also increase with increasing milling time. In some embodiments, after the ball-milling step, a phase rich in the second metal material may be observed.

[0035] In some embodiments, as described herein, mechanically alloying the homogenous mixture can reduce both particulate size and grain size. Without wishing to be bound by any particular theory, mechanically alloying the metal powders at a lower temperature can lead to a stable phase-segregated nanocrystalline structure. In some embodiments, mechanically alloying the metal powders can lead to alloy systems having reduced grain size, increased ductility, increased toughness, increased sinterability, and/or reduced reactivity due to oxidation potential during passivation at step 104. Without wishing to be bound by any particular theory, the NCM powder can be less reactive during passivation at least in part because mechanically milling the metal powder into an alloy system can decouple grain size from particle size, leading to a much smaller specific surface area. In other words, NCM powders prepared according to methods described in the‘325 publication, the ‘381 application, and the‘383 application may have a lower specific surface area to grain boundary ratio, making it less reactive when exposed to air during passivation.

[0036] In some embodiments, particles resulting from mechanical alloying can have an average particle dimension of at least about 200 nm, at least about 300 nm, at least about 400 nm, at least about 500 nm, at least about 600 nm, at least about 700 nm, at least about 800 nm, at least about 900 nm, at least about 1 pm, at least about 2 pm, at least about 3 pm, at least about 4 pm, at least about 5 pm at least about 10 pm, at least about 20 pm, at least about 30 pm, at least about 40 pm, at least about 50 pm, at least about 60 pm, at least about 70 pm, at least about 80 pm, or at least about 90 pm. In some embodiments, particles resulting from mechanical alloying can have an average particle dimension of no more than about 100 pm, no more than about 90 pm, no more than about 80 pm, no more than about 70 pm, no more than about 60 pm, no more than about 50 pm, no more than about 40 pm, no more than about 30 pm, no more than about 20 pm, no more than about 10 pm, no more than about 5 pm, no more than about 4 pm, no more than about 3 pm, no more than about 2 pm, no more than about 1 pm, no more than about 900 nm, no more than about 800 nm, no more than about 700 nm, no more than about 600 nm, no more than about 500 nm, no more than about 400 nm, or no more than about 300 nm. Combinations of the above-referenced particle size ranges are also possible (e.g., at least about 200 nm and no more than about 100 pm or at least about 500 nm and no more than about 5 pm), inclusive of all values and ranges therebetween. In some embodiments, particles resulting from mechanical alloying can have an average particle dimension of about 200 nm, about 300 nm, about 400 nm, about 500 nm, about 600 nm, about 700 nm, about 800 nm, about 900 nm, about 1 pm, about 2 pm, about 3 pm, about 4 pm, about 5 pm, about 10 pm, about 20 pm, about 30 pm, about 40 pm, about 50 pm, about 60 pm, about 70 pm, about 80 pm, about 90 pm, or about 100 pm.

[0037] In some embodiments, resulting alloyed metal powders can have a grain size of at least about 2 nm, at least about 3 nm, at least about 4 nm, at least about 5 nm, at least about 6 nm, at least about 7 nm, at least about 8 nm, at least about 9 nm, at least about 10 nm, at least about 20 nm, at least about 30 nm, at least about 40 nm, at least about 50 nm, at least about 60 nm, at least about 70 nm, at least about 80 nm, at least about 90 nm, at least about 100 nm, at least about 200 nm, at least about 300 nm, at least about 400 nm, at least about 500 nm, at least about 600 nm, at least about 700 nm, at least about 800 nm, at least about 900 nm, at least about 1 pm, at least about 2 pm, at least about 3 pm, or at least about 4 pm. In some embodiments, resulting alloyed metal powders can have a grain size of no more than about 5 pm, no more than about 4 mih, no more than about 3 mih, no more than about 2 mih, no more than about 1 mih, no more than about 900 nm, no more than about 800 nm, no more than about 700 nm, no more than about 600 nm, no more than about 500 nm, no more than about 400 nm, no more than about 300 nm, no more than about 200 nm, no more than about 100 nm, no more than about 90 nm, no more than about 80 nm, no more than about 70 nm, no more than about 60 nm, no more than about 50 nm, no more than about 40 nm, no more than about 30 nm, no more than about 20 nm, no more than about 10 nm, no more than about 9 nm, no more than about 8 nm, no more than about 7 nm, no more than about 6 nm, no more than about 5 nm, no more than about 4 nm, or no more than about 3 nm. Combinations of the above-referenced grain sizes are also possible (e.g., at least about 2 nm and no more than about 5 mih or at least about 5 nm and no more than about 100 nm), inclusive of all values and ranges therebetween. In some embodiments, resulting alloyed metal powders can have a grain size of about 2 nm, about 3 nm, about 4 nm, about 5 nm, about 6 nm, about 7 nm, about 8 nm, about 9 nm, about 10 nm, about 20 nm, about 30 nm, about 40 nm, about 50 nm, about 60 nm, about 70 nm, about 80 nm, about 90 nm, about 100 nm, about 200 nm, about 300 nm, about 400 nm, about 500 nm, about 600 nm, about 700 nm, about 800 nm, about 900 nm, about 1 pm, about 2 pm, about 3 pm, about 4 pm, or about 5 pm.

[0038] In some embodiments, mechanically alloying such alloys can overcome the energy penalty caused by the high density of grain boundaries. The two or more metallic elements can be mechanically alloyed before sintering by milling together particulates of the metallic elements in particular proportions for some time. Processes such as high-energy ball milling favor plastic deformation mechanisms and can reduce overall processing time. Selecting the proper two or more metallic elements can also reduce the overall reactivity of the elemental and master alloy powders. High-energy ball milling can produce refined composite alloys or achieve highly homogenous powder alloy systems with very high grain density and ultra-fine or nanoscale grains.

[0039] Not only can mechanically alloying metallic powders reduce grain size and lead to more stabilized and segregated phases, it may also confer sufficient energy to the alloy system to form certain grain boundary configurations. In some embodiments, the certain grain boundary configurations can be nanometer scale amorphous layers between grains that lead to fast transport of atoms during sintering, which may accelerate sintering and reduce the required sintering temperature, a process called solid-state activated sintering. When the required sintering temperature is reduced, the ultra-fine and/or nanoscale grains may be less likely to coarsen during sintering, leading to a finished alloy system with ultra-fine and/or nanoscale grains, which may improve mechanical properties of the finished alloy.

[0040] Mechanically alloying alloy systems described herein may lead to a reduction of required sintering temperature, may lead to reduced porosity (i.e., higher density), can limit thermally activated grain growth during sintering, and/or can allow the formation of a sintered alloy system with nanostructure grains in the finished alloy. In other words, the alloy systems described herein may require a lower sintering temperature than conventional alloy systems, may be less likely to exhibit grain growth during sintering than conventional alloy systems, and/or may achieve nanostructured grains after sintering, which is not typically achieved using conventional alloy systems. In some embodiments, the as-processed powder can then be sintered according to a nano-phase separation sintering approach. The nano-phase separation sintering approach results in a shorter sintering time because the emergence of a second phase accelerates densification. Sintered alloy systems formed according to these methods can exhibit desired properties such as high strength, increased resistance, and increased corrosion and creep resistance.

[0041] In some embodiments, milling of the stabilizer element and the activator element may produce a non-equilibrium phase. The non-equilibrium phase may contain a solid solution. The non-equilibrium phase may be a supersaturated phase. A“supersaturated phase” may be a non-equilibrium phase that includes the activator element forcibly dissolved in the first metal material in an amount that exceeds the amount of activator element that could be otherwise dissolved in an equilibrium phase. In some embodiments, the supersaturated phase may be the only phase present after the ball-milling process. In some embodiments, a second phase rich in the activator element may be present after ball milling.

[0042] In some embodiments, after mechanically alloying, the surfaces of the NCM powder particles can be passivated at step 104. In some embodiments, the surfaces of the NCM powder particles can be passivated with a thin oxide layer to reduce further oxidation of the powder particles. In some embodiments, passivation can result in the formation of a hydroxide layer, boride layer, nitride layer, hydride layer, combinations thereof, or the like on the surface of NCM powder particles. In some embodiments, passivation can occur by cooling the powder (e.g., to below 100 °C) and then introducing a mildly oxidizing gas. In some embodiments, the mildly oxidizing gas can include carbon dioxide, oxygen diluted in an inert gas, water vapor, or combinations thereof. In some embodiments, passivation can be carried out by “burping” the powder, which includes continuing to mix the powder in the mill while introducing small amounts of oxygen into the mill (e.g., by opening an access port for a short amount of time) over a longer duration of mixing. In some embodiments, one method by which to predict the completion of passivation is to monitor the increase in an air temperature or a powder temperature within the mill after each time an oxidizing gas is introduced until introducing additional oxidizing gas does not result in an increase in temperature within the mill.

[0043] Resulting alloyed metal powders can have a grain size in the nanometer range - i.e., smaller than about 100 nm: e.g., smaller than or equal to about 90 nm, about 80 nm, about 70 nm, about 60 nm, about 50 nm, about 40 nm, about 30 nm, about 20 nm, about 15 nm, about 10 nm, or smaller. In some embodiments, the nanocrystalline material may be a poly crystalline material. In some embodiments, the nanocrystalline material may be a single crystalline material. In some embodiments, nanocrystalline metal particles can be used to accelerate sintering.

[0044] In some embodiments, resulting alloyed metal powders can have a grain size of at least about 10 nm, at least about 20 nm, at least about 30 nm, at least about 40 nm, at least about 50 nm, at least about 60 nm, at least about 70 nm, at least about 80 nm, at least about 90 nm, at least about 100 nm, at least about 200 nm, at least about 300 nm, at least about 400 nm, at least about 500 nm, at least about 600 nm, at least about 700 nm, at least about 800 nm, at least about 900 nm, at least about 1 pm, at least about 2 pm, at least about 3 pm, at least about 4 pm, at least about 5 pm, at least about 6 pm, at least about 7 pm, at least about 8 pm, at least about 9 pm, at least about 10 pm, at least about 20 pm, at least about 30 pm, at least about 40 pm, at least about 50 pm, at least about 60 pm, at least about 70 pm, at least about 80 pm, or at least about 90 pm. In some embodiments, resulting alloyed metal powders can have a grain size of no more than about 100 pm, no more than about 90 pm, no more than about 80 pm, no more than about 70 pm, no more than about 60 pm, no more than about 50 pm, no more than about 40 pm, no more than about 30 pm, no more than about 20 pm, no more than about 10 pm, no more than about 9 pm, no more than about 8 pm, no more than about 7 pm, no more than about 6 pm, no more than about 5 pm, no more than about 4 pm, no more than about 3 pm, no more than about 2 pm, no more than about 1 pm, no more than about 900 nm, no more than about 800 nm, no more than about 700 nm, no more than about 600 nm, no more than about 500 nm, no more than about 400 nm, no more than about 300 nm, no more than about 200 nm, no more than about 100 nm, no more than about 90 nm, no more than about 80 nm, no more than about 70 nm, no more than about 60 nm, no more than about 50 nm, no more than about 40 nm, no more than about 30 nm, or no more than about 20 nm. Combinations of the above-referenced grain sizes are also possible (e.g., at least about 10 nm and no more than about 100 pm or at least about 50 nm and no more than about 1 pm), inclusive of all values and ranges therebetween. In some embodiments, resulting alloyed metal powders can have a grain size of about 10 nm, about 20 nm, about 30 nm, about 40 nm, about 50 nm, about 60 nm, about 70 nm, about 80 nm, about 90 nm, about 100 nm, about 200 nm, about 300 nm, about 400 nm, about 500 nm, about 600 nm, about 700 nm, about 800 nm, about 900 nm, about 1 pm, about 2 pm, about 3 pm, about 4 pm, about 5 pm, about 6 pm, about 7 pm, about 8 pm, about 9 pm, about 10 pm, about 20 pm, about 30 pm, about 40 pm, about 50 pm, about 60 pm, about 70 pm, about 80 pm, about 90 pm, or about 100 pm.

[0045] In some embodiments, the plurality of NCM particulates (i.e., the NCM powder) and the binder can be mixed at step 106 to form the molding feedstock and heated at step 108 to form a flowable composition that is then injected into a mold cavity at step 110, where it cools and hardens to the configuration of the cavity to form a green body. In some embodiments, the binder can improve the flowability of the molding feedstock during injection molding. In some embodiments, the binder can include at least one of a crosslinking agent, a polymeric material, a plastic, a water-soluble polymer, polyolefin, a polystyrene, ethylene vinyl acetate, a wax, a polyoxymethylene copolymer, polyethylene, linear low-density polyethylene, high-density polyethylene, polypropylene, isostatic polypropylene, atactic polypropylene, a polyacetal, polyoxymethylene, a starch, a synthetic wax, a natural wax, ethylene distearamide, Acrowax^®, stearic acid, or combinations thereof. In some embodiments, the binder system can be a grade binder system that is removed progressively during debinding. In some embodiments, the binder can be a binder system including more than one of a polymer and a wax. In some embodiments, the binder system can include a polymer having a melting point and a boiling point and a wax having a melting point different than the melting point of the polymer and a boiling point different from the boiling point of the polymer. In some embodiments, the polymer can have a rate of chemical solvation when in contact with a particular chemical debinding agent that is greater or lesser than the rate of chemical solvation for the wax. Without wishing to be bound by any particular theory, the use of a graded binder system can allow for a more staged or gradual rate of debinding, which can result in a lower rate of porosity, especially air-entrained porosity within the binder-free compounded article. In addition, in some embodiments, using a graded binder system can allow the viscosity of the molding feedstock to be tuned by increasing or decreasing the temperature of the molding feedstock at different points during NMIM. In some embodiments, during the debinding step, the staged debinding of first a wax material and second a polymeric material can help avoid cracking due to the lack of avenues for removal of the polymeric material. In other words, in some embodiments, the removal first of the wax provides voids in the partially debinded article through which the polymeric material can escape when the temperature rises above the melting temperature of the polymeric material.

[0046] In some embodiments, the molding feedstock can include, in addition to or instead of the binder, a wetting agent, a lubricant, a surfactant, a dispersion agent, a crosslinking agent, a coupling agent, combinations thereof, and/or other compounds. In some embodiments, the additive or additives, such as those listed above, can be added to increase the flowability of the molding feedstock, the compoundability of the molding feedstock, the compounded article density that can be achieved, the debindability of the compounded article, the sinterability of the debindered article, and/or the density, durability, or other mechanical properties of the sintered article manufactured, in part, using NMIM of nanocrystalline metal alloy powders. In some embodiments, the coupling agent can include titanium-derived coupling agents that act as a molecular bridge at the interface between two substrates, a mixture of filler/fiber and an organic polymer matrix, neopentyl(diallyl)oxy, tri(dioctyl)pyrophosphate titanate, titanium IV 2,2 (bis 2-propenolatomethyl)butanolato, tris (dioctyl) pyrophosphate-O, Ken-React^® LICA^® 38 (Kenrich Petrochemicals, Inc.), Ken-React^® KR^® 38S (Kenrich Petrochemicals, Inc.), neopentyl(diallyl)oxy, tri(dioctyl)phosphate titanate, titanium IV 2,2 (bis 2- propenolatomethyl)butanolato, tris(dioctyl) phosphate-O), Ken-React^® LICA^® 12 (Kenrich Petrochemicals, Inc.), Ken-React^® KR^® 12 (Kenrich Petrochemicals, Inc.), combinations thereof, and the like.

[0047] In some embodiments, the molding feedstock can include an additive or additives content of at least about 0.1 wt%, at least about 0.5 wt%, at least about 1 wt%, at least about 2 wt%, at least about 3 wt%, at least about 4 wt%, at least about 5 wt%, at least about 6 wt%, at least about 7 wt%, at least about 8 wt%, at least about 9 wt%, at least about 10 wt%, at least about 20 wt%, at least about 30 wt%, or at least about 40 wt%. In some embodiments, the molding feedstock can include an additive or additives content of no more than about 50 wt%, no more than about 40 wt%, no more than about 30 wt%, no more than about 20 wt%, no more than about 10 wt%, no more than about 9 wt%, no more than about 8 wt%, no more than about 7 wt%, no more than about 6 wt%, no more than about 5 wt%, no more than about 4 wt%, no more than about 3 wt%, no more than about 2 wt%, no more than about 1 wt%, or no more than about 0.5 wt%. Combinations of the above referenced additive or additives content are also possible (e.g., at least about 0.1 wt% and no more than about 50 wt% or at least about 1 wt% and no more than about 10 wt%).

[0048] One particular issue found when using the NCM powder and some of the binder systems disclosed herein is the difficulty of wetting the NCM powder with the binder system. In some embodiments, a coupling agent can be added to the binder system to facilitate wetting of the NCM powder with the binder system. In some embodiments, the coupling agent can include a surfactant. In some embodiments, the addition of a coupling agent can help increase solids loading by reducing the amount of binder necessary to coat all particles of the NCM powder. In some embodiments, the coupling agent can be less than about 1 wt% of the binder system, about 2 wt%, about 3 wt%, about 4 wt%, about 5 wt%, about 6 wt%, about 7 wt%, about 8 wt%, about 9 wt%, or 10 wt%, inclusive of all values and ranges therebetween. Without wishing to be bound by any particular theory, the use of a coupling agent such as a surfactant with the binder system can increase solids loading by about 1 vol% to about 10 vol%. In some embodiments, the surfactant can include sodium dodecyl sulfate, sodium lauryl ether sulfate, Triton X-100 (4-[l, l,3,3-tetramethylbutyl]phenyl-polyethylene glycol), dioctyl sodium sulfosuccinate, perfluorooctanesulfonate, perfluorobutanesulfonate, alkyl ether phosphates, fluorosurfactants, siloxane surfactants, ammonium lauryl sulfate, sodium myreth sulfate, sodium laureth sulfate, sodium lauroyl sarcosinate, sodium stearate, perfluorononanoate, perfluorooctanoate, octenide dihydrochloride, cetrimonium bromide, cetylpyridinium chloride, benzalkonium chloride, benzethonium chloride, any other suitable surfactant, and combinations thereof.

[0049] Preparation of the molding feedstock at step 106 includes mixing the alloyed metal powder and the binder to form the molding feedstock. In some embodiments, mixing can be carried out using an attritor mill, a ball mill, a shear mixer, conical mixer, vertical cone mixer, powder blender, vertical mixer, vertical twin-shaft mixer, vertical single-shaft mixer, ribbon blender, drum powder mixer, continuous granulator, ring-layer mix-pelletizer, container mixer, and any other suitable mixing, blending, combining, disagglomeration, and/or milling equipment.

[0050] In some embodiments, the nanocrystalline alloy particles and the binder can be combined in a container and agitated or stirred, or any other type or form of mixing, shaking, centrifuging, or blending. In some embodiments, a mixing method can include mechanically working the mixture. In some embodiments, the resulting mixture of the nanocrystalline alloy particles and the binder can be in the form of a dry mixture, a liquid, a semi-solid, a slurry, a gel, or a paste.

[0051] In some embodiments, the molding feedstock can include between about 20 wt% and about 80 wt% of the metal powder, about 25 wt% to about 75 wt%, about 30 wt% to about 70 wt%, about 35 wt% to about 65 wt%, about 40 wt% to about 60 wt%, about 45 wt% to about 55 wt%, or about 30 wt% to about 60 wt%, inclusive of all values and ranges therebetween. In some embodiments, the molding feedstock can include greater than about 10 wt% of the metal powder, greater than about 15 wt%, greater than about 20 wt%, greater than about 25 wt%, greater than about 30 wt%, greater than about 35 wt%, greater than about 40 wt%, greater than about 45 wt%, greater than about 50 wt%, greater than about 55 wt%, greater than about 60 wt%, greater than about 65 wt%, greater than about 70 wt%, greater than about 75 wt%, greater than about 80 wt%, or greater than about 85 wt%, inclusive of all values and ranges therebetween. In some embodiments, the molding feedstock can include less than about 80 wt% of the metal powder, less than about 75 wt%, less than about 70 wt%, less than about 65 wt%, less than about 60 wt%, less than about 55 wt%, less than about 50 wt%, less than about 45 wt%, less than about 40 wt%, less than about 35 wt%, less than about 30 wt%, less than about 25 wt%, or less than about 20 wt%, inclusive of all values and ranges therebetween.

[0052] In some embodiments, the molding feedstock can include at least about 48 vol%, at least about 49 vol%, at least about 50 vol%, at least about 51 vol%, at least about 52 vol%, at least about 53 vol%, at least about 54 vol%, at least about 55 vol% , at least about 56 vol% , at least about 57 vol% , at least about 58 vol% , at least about 59 vol% , at least about 60 vol% , at least about 61 vol% , at least about 62 vol% , at least about 63 vol% , or at least about 64 vol% of the metal powder. In some embodiments, the molding feedstock can include no more than about 65 vol%, no more than about 64 vol%, no more than about 63 vol%, no more than about 62 vol%, no more than about 61 vol%, no more than about 60 vol%, no more than about 59 vol%, no more than about 58 vol%, no more than about 57 vol%, no more than about 56 vol%, no more than about 55 vol%, no more than about 54 vol%, no more than about 53 vol%, no more than about 52 vol%, no more than about 51 vol%, no more than about 50 vol%, or no more than about 49 vol% of the metal powder. Combinations of the above referenced molding feedstock metal powder contents are also possible (e.g., at least about 48 vol% and no more than about 65 vol% or at least about 50 vol% and no more than about 52 vol%), inclusive of all values and ranges therebetween. In some embodiments, the molding feedstock can include about 48 vol%, about 49 vol%, about 50 vol%, about 51 vol%, about 52 vol%, about 53 vol%, about 54 vol%, about 55 vol%, about 56 vol%, about 57 vol%, about 58 vol%, about 59 vol%, about 60 vol%, about 61 vol%, about 62 vol%, about 63 vol%, about 64 vol%, or about 65 vol% of the metal powder.

[0053] In some embodiments, the molding feedstock can include between about 30 vol% and about 90 vol% of the metal powder, about 35 vol% and about 85 vol%, about 40 vol% and about 80 vol%, about 45 vol% and about 75 vol%, about 50 vol% and about 70 vol%, about 55 vol% and about 65 vol%, about 60 vol% and about 65 vol%, about 60 vol% and about 64 vol%, about 30 vol% and about 85 vol%, about 30 vol% and about 80 vol%, about 30 vol% and about 75 vol%, about 30 vol% and about 70 vol%, about 30 vol% and about 65 vol%, about 30 vol% and about 60 vol%, about 30 vol% and about 55 vol%, about 30 vol% and about 50 vol%, about 30 vol% and about 45 vol%, about 30 vol% and about 40 vol%, about 50 vol% and about 90 vol%, about 55 vol% and about 90 vol%, about 60 vol% and about 90 vol%, about 65 vol% and about 90 vol%, or about 70 vol% and about 90 vol%, inclusive of all values and ranges therebetween.

[0054] In some embodiments, the molding feedstock can include between about 20 wt% and about 80 wt% of the binder, about 25 wt% to about 75 wt%, about 30 wt% to about 70 wt%, about 35 wt% to about 65 wt%, about 40 wt% to about 60 wt%, about 45 wt% to about 55 wt%, or about 30 wt% to about 60 wt%, inclusive of all values and ranges therebetween. In some embodiments, the molding feedstock can include greater than about 10 wt% of the binder, greater than about 15 wt%, greater than about 20 wt%, greater than about 25 wt%, greater than about 30 wt%, greater than about 35 wt%, greater than about 40 wt%, greater than about 45 wt%, greater than about 50 wt%, greater than about 55 wt%, greater than about 60 wt%, greater than about 65 wt%, greater than about 70 wt%, greater than about 75 wt%, greater than about 80 wt%, or greater than about 85 wt%, inclusive of all values and ranges therebetween. In some embodiments, the molding feedstock can include less than about 80 wt% of the binder, less than about 75 wt%, less than about 70 wt%, less than about 65 wt%, less than about 60 wt%, less than about 55 wt%, less than about 50 wt%, less than about 45 wt%, less than about 40 wt%, less than about 35 wt%, less than about 30 wt%, less than about 25 wt%, or less than about 20 wt%, inclusive of all values and ranges therebetween.

[0055] In some embodiments, the molding feedstock can include at least about 45 wt %, at least about 46 wt%, at least about 47 wt%, at least about 48 wt%, at least about 49 wt%, at least about 50 wt%, or at least about 51 wt% of the binder. In some embodiments, the molding feedstock can include no more than about 52 wt%, no more than about 51 wt%, no more than about 50 wt%, no more than about 49 wt%, no more than about 48 wt%, no more than about 47 wt%, or no more than about 46 wt% of the binder. Combinations of the above referenced molding feedstock binder contents are also possible (e.g., at least about 45 wt% and no more than about 52 wt% or at least about 48 wt% and no more than about 50 wt%). In some embodiments, the molding feedstock can include about 45 wt%, about 46 wt%, about 47 wt%, about 48 wt%, about 49 wt%, about 50 wt%, about 51 wt%, or about 52 wt% of the binder.

[0056] In some embodiments, the relative weight ratio, volumetric ratio, and/or atomic ratio of metal powder to binder can be between about 1 :5 and about 5: 1, between about 1 :4 and about 4: 1, between about 1 :3 and about 3 : 1, between about 1 :2 and about 2: 1, or about 1 : 1, inclusive of all values and ranges therebetween.

[0057] In some embodiments, the use of NCM alloys at step 106 can facilitate higher binder loadings. In some embodiments, higher binder loading rates can result in a more flowable molding feedstock than conventional molding feedstocks. In some embodiments, the use of NCM powders can result in less defects after debinding than green bodies formed using conventional molding feedstocks and conventional MIM processes. Likewise, the nanocrystalline metal powders used herein are more compoundable than conventional metal powders due to improved morphological properties including particle size distribution and specific surface area. For example, in some embodiments, the mechanical milling processes described herein result in a metal powder that can have a highly tailored particle size distribution. In other words, in some embodiments, if one would like to increase compounding density (e.g., ease of compounding) for a particular system, mold design, metal alloy system, binder, or for another reason, a wider particle size distribution can be accomplished by milling for less time. In some embodiments, if one would like to improve the ease or rapidity of sintering, a narrower particle size distribution can be accomplished by higher-energy milling (e.g., milling for a longer duration and perhaps at a lower speed or temperature). In some embodiments, the use of NCM powders can result in a metal alloy article with a higher relative density than a process that does not use NCM powders.

[0058] The use of nanocrystalline metals and alloys provide substantially improved properties relatively to traditional microcrystalline metals and alloys of the same chemistry, including improvements in mechanical properties, corrosion performance, and magnetic properties. Traditional metal forming and sintering techniques typically require high temperatures, which can lead to undesired grain growth in nanocrystalline metals and alloys. Producing bulk nanocrystalline materials with high relative densities and limited grain growth can thus be challenging and difficult to achieve. Additionally, powder metallurgy sintering techniques often also require applied pressure to consolidate the final metal and alloy products, which may limit the design of the pre-sintered mold to simple shapes and forms.

[0059] In some embodiments, the molding feedstock can be configured to have particular rheological specifications including but not limited to pseudo-plasticity, viscosity, shear-strength, and flowability. In some embodiments, the molding feedstock can include a rheological additive to modify the flowability of the molding feedstock and/or the mechanical properties of the molded structure (e.g., increasing the tensile strength of the molded structure so it retains substantially the same shape prior to sintering). In some embodiments, the rheological additive can survive the debinding and sintering process and can have an effect on the hardness/toughness of the sintered material.

[0060] In some embodiments, the NCM alloy used as the metal powder can increase the compoundability of the molding feedstock during injection, which can increase the initial density of the article after injection. Without wishing to be bound by any particular theory, the NCM alloy may catalyze reactions with the binder, which is typically difficult to compound, to make it easier to compound the flowable molding feedstock. In some embodiments, the NCM powders described herein can have a specific surface area that is orders of magnitude lower than that of conventional nanostructured metal powders. In other words, the NCM powders described herein have a much lower specific surface area to volume ratio and are less likely to violently react during passivation and/or injection molding. In other words, as compared to conventional nanostructured metal powders, NCM powders described herein are unique because more of the grain boundaries are directly abutting other grain boundaries rather than being exposed to the air due to the mechanical alloying of the powders. Without wishing to be bound by any particular theory, because the mechanically alloying of the NCM powders described herein, interparticle nanogranular structures can be formed without the particles fracturing. In other words, a large amount of grain boundaries are formed instead of a large amount of surfaces.

[0061] In some embodiments, the NCM powder can have a specific surface area value of between about 1 m²/g and about 50 m²/g, between about 1 m²/g and about 25 m²/g, between about 1 m²/g and about 10 m²/g, and between about 1 m²/g and about 5 m²/g, inclusive of all values and ranges therebetween. Conversely, conventional nanostructured metal powders often have a specific surface area value of between about 100 m²/g and about 300 m²/g or greater. The significant reduction in specific surface area achieved for the NCM powders described herein have significant implications for reducing reactivity of the NCM powders and for the overall safety of the metallurgical processes and systems described herein.

[0062] In some embodiments, in order to prepare the molding feedstock for injection into the mold at step 110, the molding feedstock can be heated at step 108 until the binder melts but not to the point that binder begins boiling and/or volatilizing. In some embodiments, the heating can be accomplished be direct or indirect heating, for example, using a flame, shearing and frictional heating due to the design and action of the reciprocating screw, conductive heating, irradiation, or any other suitable method. In some embodiments, the molding feedstock can be heated and mixed at the same time, such as in a screw mixer. In some embodiments, the molding feedstock can be stored in an overhead hopper or other container and disposed into an extruder or screw mixer that heats the mixture to make it flowable, and transports the flowable molding feedstock to the injection device.

[0063] In some embodiments, the injection device used at step 1 10 can be a nozzle, a port, or any other such opening that connects the injection device to either the cavity directly, to a sprue configured to guide the flowable molding feedstock into the cavity, or to a sprue configured to guide the flowable molding feedstock into runners that are connected to multiple cavities. For smaller articles, it may be more economical to fill more than one cavity concurrently. In some embodiments, the use of a sprue and/or runners to facilitate the communication of flowable molding feedstock into the cavities can lead to higher molded waste. In some embodiments, molded waste (e.g., sprues, runners, defect parts, etc.) can be reground and mixed with new molding feedstock.

[0064] In some embodiments, the mold can include a movable landing surface that partially defines the cavity to be filled with flowable molding feedstock during injection molding. In some embodiments, the mold can include a plurality of vents disposed within the landing surface that let air escape as the flowable molding feedstock is injected into the cavity. In some embodiments, the plurality of vents can be ground into the landing surface at a depth of less than about 50 microns, about 40 microns, about 30 microns, about 20 microns or smaller, such that the flowable molding feedstock is unable to escape from the cavity through the plurality of vents. In some embodiments, the mold can include a second surface that partially defines the cavity and is immovable relative to the injection device. In some embodiments, the second surface of the mold can include cooling lines beneath the mold surface configured to facilitate rapid cooling of the injected flowable molding feedstock in order to form a molded structure. [0065] In some embodiments, the mold includes a clamp connected to the movable first mold surface and configured to keep the mold closed during injection and formation of the molded structure. In some embodiments, the mold includes an ejection pin or a plurality of injection pins that facilitate the ejection of the molded structure from the mold once the clamp moves the first surface of the mold away from the fixed mold surface.

[0066] In some embodiments, the molded structure can be cooled to any temperature between about the melting point of the binder and about room temperature such that the binder solidifies and the molded structure is capable of retaining the desired shape while being handled. In some embodiments, the cooling can be accomplished by using cooling fluid channels disposed within or about the mold structure.

[0067] In some embodiments, the molded structure formed according to the NMIM process described herein can be substantially free of voids. In some embodiments, the molded structure formed according to the NMIM process described herein can be a highly complex geometrical structure, which cannot be produced by any conventional green body processing or preparation techniques.

[0068] In some embodiments, the molded structure may retain the sprue and/or runners connected to the article, and therefore the retained sprue and/or runners could be removed before debinding of the molded structure. In some embodiments, the sprue can be heated such that the flowable molding feedstock within the sprue remains flowable (e.g., the binder remains at least partially molten) during the solidification and ejection of the molded structure, and therefore the sprue and/or runners are not retained with the molded structure.

[0069] In some embodiments, the molding feedstock can be formed into the molded structure (green body) by direct extrusion, indirect extrusion, impact extrusion, hydrostatic extrusion, cold extrusion, hot extrusion, casting, tape casting, drop casting, knife coating, spreading using a doctor blade, or in any other suitable manner. In some embodiments, the molding feedstock can be formed into any suitable form factor, such as, for example, a rod, a sheet, a tube, an I-shape, any other suitable polygonal or planar structure, or combinations thereof.

[0070] The molded structure is then further processed by chemically, thermally, and/or catalytically debinding the molded structure at step 112. In some embodiments, debinding can be accomplished by soaking the molded structure in a solvent. In some embodiments, debinding can be accomplished by introducing a highly concentrated acidic gas that decomposes the binder so it can flow easily out of the interconnected metal particle structure of the molded structure. In some embodiments, debinding can be accomplished by heating the part to above the melting point of the binder or binder mixture such that the binder flows out of the interconnected metal particle structure of the molded structure.

[0071] In some embodiments, the thermal debinding process can be done by heating the molded structure to a debinding temperature of at least about 400 °C, at least about 450 °C, at least about 500 °C, at least about 550 °C, at least about 600 °C, at least about 650 °C, at least about 700 °C, at least about 750 °C, at least about 800 °C, at least about 850 °C, at least about 900 °C, at least about 950 °C, at least about 1,000 °C, or at least about 1,050 °C. In some embodiments, the thermal debinding process can be done by heating the intermediate material to a debinding temperature of no more than about 1,100 °C, no more than about 1,050 °C, no more than about 1,000 °C, no more than about 950 °C, no more than about 900 °C, no more than about 850 °C, no more than about 800 °C, no more than about 750 °C, no more than about 700 °C, no more than about 650 °C, no more than about 600 °C, no more than about 550 °C, no more than about 500 °C, or no more than about 450 °C.

[0072] Combinations of the above referenced ranges for the debinding temperature are also possible (e.g., at least about 400 °C and no more than about 1, 100 °C or at least about 450 °C and no more than about 900 °C). In some embodiments, the debinding temperature can be about 400 °C, about 450 °C, about 500 °C, about 550 °C, about 600 °C, about 650 °C, about 700 °C, about 750 °C, about 800 °C, about 850 °C, about 900 °C, about 950 °C, about 1,000 °C, about 1,050 °C, or about 1,100 °C.

[0073] In some embodiments, the molded structure after debinding can retain the net shape of the molded structure while the overall dimensions are reduced. In other words, dimensions of particular features of the molded structure can be substantially the same on a relative basis while the overall size of the molded structure after debinding can be less than the molded structure. In some embodiments, this shrinkage of the molded structure after debinding can be characterized as a volumetric reduction and can be characterized by displacement measurement techniques. In some embodiments, shrinkage due to debinding can be at least about 0.01 vol%, at least about 0.02 vol%, at least about 0.03 vol%, at least about 0.04 vol%, at least about 0.05 vol%, at least about 0.06 vol%, at least about 0.07 vol%, at least about 0.08 vol%, at least about 0.09 vol%, at least about 0.1 vol%, at least about 0.2 vol%, at least about 0.3 vol%, at least about 0.4 vol%, at least about 0.5 vol%, at least about 0.6 vol%, at least about 0.7 vol%, at least about 0.8 vol%, at least about 0.9 vol%, at least about 1 vol%, at least about 2 vol%, at least about 3 vol%, or at least about 4 vol%. In some embodiments, shrinkage due to debinding can be no more than about 5 vol%, no more than about 4 vol%, no more than about 3 vol%, no more than about 2 vol%, no more than about 1 vol%, no more than about 0.9 vol%, no more than about 0.8 vol%, no more than about 0.7 vol%, no more than about 0.6 vol%, no more than about 0.5 vol%, no more than about 0.4 vol%, no more than about 0.3 vol%, no more than about 0.2 vol%, no more than about 0.1 vol%, no more than about 0.09 vol%, no more than about 0.08 vol%, no more than about 0.07 vol%, no more than about 0.06 vol%, no more than about 0.05 vol%, no more than about 0.04 vol%, no more than about 0.03 vol%, or no more than about 0.02 vol%. Combinations of the above-referenced ranges of shrinkage due to debinding are also possible (e.g., at least about 0.01 vol% and no more than about 5 vol% or at least about 0.1 vol% and no more than about 1 vol%), inclusive of all values and ranges therebetween. In some embodiments, shrinkage due to debinding can be about 0.01 vol%, about 0.02 vol%, about 0.03 vol%, about 0.04 vol%, about 0.05 vol%, about 0.06 vol%, about 0.07 vol%, about 0.08 vol%, about 0.09 vol%, about 0.1 vol%, about 0.2 vol%, about 0.3 vol%, about 0.4 vol%, about 0.5 vol%, about 0.6 vol%, about 0.7 vol%, about 0.8 vol%, about 0.9 vol%, about 1 vol%, about 2 vol%, about 3 vol%, about 4 vol%, or about 5 vol%.

[0074] The molded structure after debinding is then sintered at step 114 to form the finished metal article. Sintering is a complex process that may include microstructure change due in part to several different diffusion mechanisms. In some embodiments, this complex sintering process may be distinguished into three stages based on the evolution of the micro structure: initial, intermediate, and final stage. The initial stage may begin at a low temperature when necks are created between particles. The necks may be created through surface diffusion and may result in a small increase in density. The initial stage may correlate to less than 3% linear shrinkage. The intermediate stage may produce considerable densification. The densification in the intermediate stage may be up to a relative density of about 93 %. During the final stage, isolated pores may be formed and then removed. In the final stage, volume diffusion may be predominant. In some embodiments, the use of nanocrystalline metal alloy systems can increase the sintering rate and the density of sintered articles.

[0075] In some embodiments, sintering can be conducted in an atmosphere containing hydrogen, a vacuum, air, or an inert gas atmosphere. In some embodiments, sintering can be conducted in an atmosphere containing mixtures of inert gases and reactive gases or mixtures of reactive gases. The sintering atmosphere may affect the sinterability of some alloy powders. For example, hydrogen-containing atmospheres can be used for sintering tungsten powder, producing a relatively high-density material, but may not be suitable for other alloy systems.

[0076] In some embodiments, a high sintering temperature may be employed for a short sintering time to produce the sintered material. In some embodiments, a comparably lower sintering temperature may be employed for a longer sintering time to produce a sintered material that is densified to the same degree. In some embodiments, extended sintering times or elevated sintering temperatures may result in an undesirable increase in grain size. In some embodiments, the sintering may be a pressureless sintering process. In some embodiments, the sintering mechanism described herein allows the production of fully dense sintered ultra-fine and nanocrystalline materials even in the absence of external pressure applied during the sintering process.

[0077] In some embodiments, the sintering can be conducted at a temperature of at least about 1,000 °C, at least about 1, 100 °C, at least about 1,200 °C, at least about 1,300 °C, at least about 1,400 °C, at least about 1,500 °C, at least about 1,600 °C, at least about 1,700 °C, at least about 1,800 °C, or at least about 1,900 °C. In some embodiments, the sintering can be conducted at a temperature of no more than about 2,000 °C, no more than about 1,900 °C, no more than about 1,800 °C, no more than about 1,700 °C, no more than about 1,600 °C, no more than about 1,500 °C, no more than about 1,400 °C, no more than about 1,300 °C, no more than about 1,200 °C, or no more than about 1, 100 °C. Combinations of the above-referenced sintering temperatures are also possible (e.g., at least about 1,000 °C and no more than about 2,000 °C or at least about 1,200 °C and no more than about 1,800 °C), inclusive of all values and ranges therebetween. In some embodiments, sintering can be conducted at a temperature of about 1,000 °C, about 1,100 °C, about 1,200 °C, about 1,300 °C, about 1,400 °C, about 1,500 °C, about 1,600 °C, about 1,700 °C, about 1,800 °C, about 1,900 °C, or about 2,000 °C. In some embodiments, thermal debinding and sintering can occur simultaneously, or as part of a single process step.

[0078] In some embodiments, the sintering can have a duration of at least about 30 minutes, at least about 1 hour, at least about 2 hours, at least about 3 hours, at least about 4 hours, at least about 5 hours, at least about 6 hours, at least about 7 hours, at least about 8 hours, at least about 9 hours, at least about 10 hours, at least about 12 hours, at least about 15 hours, at least about 20 hours, or at least about 24 hours. In some embodiments, the sintering can have a duration of no more than about 25 hours, no more than about 24 hours, no more than about 20 hours, no more than about 15 hours, no more than about 12 hours, no more than about 10 hours, no more than about 9 hours, no more than about 8 hours, no more than about 7 hours, no more than about 6 hours, no more than about 5 hours, no more than about 4 hours, no more than about 3 hours, no more than about 2 hours, or no more than about 1 hour. Combinations of the above-referenced sintering times are also possible (e.g., at least about 30 minutes and no more than about 25 hours, or at least about 1 hour and no more than about 10 hours), inclusive of all values and ranges therebetween. In some embodiments, the sintering can have a duration of about 30 minutes, about 1 hour, about 2 hours, about 3 hours, about 4 hours, about 5 hours, about 6 hours, about 7 hours, about 8 hours, about 9 hours, about 10 hours, about 12 hours, about 15 hours, about 20 hours, about 24 hours, or about 25 hours.

[0079] In some embodiments, the molding feedstock can be a plastically deforming material produced when combining NCM powders and the binder system at an elevated temperature above the melting temperature of the binder system. In some embodiments, the plastic nature of the molding feedstock can enable a more uniform molded structure, a more uniform debinded green body density, and more uniform sintering. Without wishing to be bound by any particular theory, by sintering at a lower temperature, as described in the‘325 publication, the microstructure of the sintered article can be controlled. In some embodiments, at lower sintering temperatures, a finer microstructure can be achieved, which may reduce defects in the finished article and lead to increased hardness. In some embodiments, the sintering temperature ramp rate and/or peak temperature hold time can be changed to tune the formation of a particular microstructure and/or optimize the mechanical properties of the article. For example, in some embodiments, depending upon the cross-sectional thickness of a complex article being sintered, the ramp rate can be slowed down such that substantially uniform heating of all parts of the article is achieved. Without wishing to be bound by any particular theory, a lower sintering temperature and a slower temperature ramp rate during sintering can lead to less instances of differential sintering and a lower rate of article cracking after sintering.

[0080] In some embodiments, the sintered article may exhibit a relative density of greater than or equal to about 75 % when compared to the particle density of the nanocrystalline metal particles- e.g., at least about 80 %, at least about 85 %, at least about 90 %, at least about 91 %, at least about 92 %, at least about 93 %, at least about 94 %, at least about 95 %, at least about 96 %, at least about 97 %, at least about 98 %, at least about 99 %, or at least about 99.9 %, inclusive of all values and ranges therebetween. In some embodiments, the relative density of the sintered material may be about 100 %. In some embodiments, the sintered material can be fully dense.

[0081] In some embodiments, the sintered article can have a relative density-to-loading index, defined as the ratio of the relative density of the sintered article to the weight percentage of the nanocrystalline metal particles in the molding feedstock For example, if the sintered article has a relative density of 96 % when compared to the particle density of the nanocrystalline metal particles, and molding feedstock includes 48 wt% nanocrystalline metal particles, then the relative density-to-loading index is calculated as 96 %/48 %, or 2.0. In some embodiments, the relative density -to-loading index is at least about 1.4, at least about 1.45, at least about 1.5, at least about 1.55, at least about 1.6, at least about 1.65, at least about 1.7, at least about 1.75, at least about 1.8, at least about 1.85, at least about 1.9, at least about 1.95, at least about 2, at least about 2.05, at least about 2.1, at least about 2.15, or at least about 2.2, inclusive of all values and ranges therebetween.

[0082] In some embodiments, the sintered article can be substantially free of voids. In some embodiments, voids can comprise less than 20 % of the volume, less than 15 %, less than 10 %, less than 9 %, less than 8 %, less than 7 %, less than 6 %, less than 5 %, less than 4 %, less than 3 %, less than 2 %, less than 1 %, less than 0.5 %, less than 0.25 %, less than 0.1 %, less than 0.05 %, or any combination of percentages or ranges thereof. In some embodiments, the sintered article can be substantially free of defects. In some embodiments, the sintered article can have a nanostructure or microstructure that is substantially similar to the nanostructure or microstructure of the nanocrystalline alloy particles before sintering. Said another way, the nanostructure or microstructure remains substantially unchanged and a minimal grain growth is observed. Structural comparison between the nanocrystalline alloy particles and the sintered article after sintering shows that the crystalline grain size is substantially maintained in certain alloy systems.

[0083] In some embodiments, the sintered article can have any suitable form factor, such as, for example, a complex shape, a rod, a sheet, an I-shape, any other suitable polygonal or planar structure, or combinations thereof. In some embodiments, the sintered article can include grain sizes that are nanostructured, ultrafme, microstructured, and/or coarse, often without a corresponding reduction in mechanical property improvements over conventional articles formed using conventional particles and the conventional MIM process. For instance, metal particles having mostly or all nanocrystalline grains can be used in the NMIM process, and after sintering, the article produced via NMIM of these metal particles having nanocrystalline grains can include bound particles having some, mostly, or all ultrafme, microstructured, or coarse grains.

[0084] In some embodiments, further densification of the sintered article can be carried out at step 116 using hot isostatic pressing processes. In some embodiments, hot isostatic pressing can be performed after pressureless sintering. In some embodiments, hot isostatic pressing can include pneumatically densifying the sintered article in a hermetic container. In some embodiments, an inert gas can be charged to the hermetic container to achieve a high pressure and heating elements can be used to increase the temperature of the sintered article. Without wishing to be bound by any particular theory, hot isostatic pressing can reduce or eliminate any remaining porosity in the sintered article without changing the net shape of the sintered article. In some embodiments, hot isostatic pressing can increase the density to about the theoretical density or the theoretical density. In some embodiments, the elimination of internal porosity in the sintered article can lead to a reduction in defects and an increase in the mechanical strength and durability of the finished article. In some embodiments, the mechanical properties that can be improved by hot isostatic pressing can also or alternatively include at least one of fatigue resistance, impact resistance, wear/abrasion resistance, ductility, and temperature resistance.

[0085] In some embodiments, hot isostatic pressing can be carried out at a pressure of between about 1,500 psi to about 100,000 psi, about 2,000 psi to about 75,000 psi, about 2,500 psi to about 60,000 psi, about 3,000 psi to about 50,000 psi, about 3,500 psi to about 40,000 psi, about 4,000 psi to about 30,000 psi, about 4,500 psi to about 20,000 psi, about 5,000 psi to about 15,000 psi, about 5,500 psi to about 10,000 psi, about 1,500 psi and about 35,000 psi, about 1,500 psi and about 30,000 psi, about 1,500 psi and about 25,000 psi, about 1,500 psi and about 20,000 psi, about 1,500 psi and about 15,000 psi, about 1,500 psi and about 10,000 psi, about 1,500 psi and about 8,000 psi, about 1,500 psi and about 7,000 psi, about 1,500 psi and about 6,000 psi, about 1,500 psi and about 5,000 psi, about 1,500 psi and about 4,000 psi, about 1,500 psi and about 3,000 psi, about 10,000 psi and about 50,000 psi, about 15,000 psi and about 50,000 psi, about 20,000 psi and about 50,000 psi, about 25,000 psi and about 50,000 psi, about 30,000 psi and about 50,000 psi, inclusive of all values and ranges therebetween. In some embodiments, hot isostatic pressing can be carried out at a pressure of greater than about 1,500 psi, about 2,000 psi, about 3,000 psi, about 4,000 psi, about 5,000 psi, about 6,000 psi, about 7,000 psi, about 8,000 psi, about 9,000 psi, about 10,000 psi, about 15,000 psi, about 20,000 psi, about 25,000 psi, about 30,000 psi, about 35,000 psi, about 40,000 psi, about 45,000 psi, greater than about 50,000 psi, greater than about 55,000 psi, greater than about 60,000 psi, greater than about 65,000 psi, greater than about 70,000 psi, greater than about 75,000 psi, greater than about 80,000 psi, greater than about 85,000 psi, greater than about 90,000 psi, greater than about 95,000 psi, or greater than about 100,000 psi, inclusive of all values and ranges therebetween. In some embodiments, hot isostatic pressing can be carried out at a pressure of less than about 100,000 psi, less than about 95,000 psi, less than about 90,000 psi, less than about 85,000 psi, less than about 80,000 psi, less than about 75,000 psi, less than about 70,000 psi, less than about 65,000 psi, less than about 60,000 psi, less than about 55,000 psi, less than about 50,000 psi, about 45,000 psi, about 40,000 psi, about 35,000 psi, about 30,000 psi, about 25,000 psi, about 20,000 psi, about 15,000 psi, about 10,000 psi, about 9,000 psi, about 8,000 psi, about 7,000 psi, about 6,000 psi, about 5,000 psi, about 4,000 psi, about 3,000 psi, about 2,000 psi, or less than about 1,500 psi, inclusive of all values and ranges therebetween.

[0086] In some embodiments, the pressure in the hot isostatic pressing vessel can be ramped up from about room temperature to the operating temperature at a rate of greater than about 10 psi/minute, 20 psi/minute, 30 psi/minute, 40 psi/minute, 50 psi/minutes, 60 psi/minutes, 70 psi/minute, 80 psi/minute, 90 psi/minute, 100 psi/minute, 150 psi/minute, 200 psi/minute, 250 psi/minute, 300 psi/minute, 400 psi/minute, 500 psi/minute, 600 psi/minute, 700 psi/minute, 800 psi/minute, 900 psi/minute, 1,000 psi/minute, 1,500 psi/minute, about 2,000 psi/minute, about 2,500 psi/minute, about 3,000 psi/minute, about 3,500 psi/minute, about 4,000 psi/minute, about 4,500 psi/minute, about 5,000 psi/minute, about 7,500 psi/minute, about 10,000 psi/minute, greater than about 20,000 psi/minute, greater than about 30,000 psi/minute, greater than about 40,000 psi/minute, greater than about 50,000 psi/minute, or greater than about 60,000 psi/minute, inclusive of all values and ranges therebetween.

[0087] In some embodiments, the temperature in the pressure vessel during hot isostatic pressing can be at least about 500 °C, at least about 750 °C, at least about 1,000 °C, at least about 1,250 °C, at least about 1,500 °C, at least about 1,750 °C, at least about 2,000 °C, or at least about 2,250 °C. In some embodiments, the temperature in the pressure vessel during hot isostatic pressing can be no more than about 2,500 °C, no more than about 2,250 °C, no more than about 2,000 °C, no more than about 1,750 °C, no more than about 1,500 °C, no more than about 1,250 °C, no more than about 1,000 °C, or no more than about 750 °C. Combinations of the above-referenced temperatures in the pressure vessel during hot isostatic pressing are also possible (e.g., at least about 500 °C and no more than about 2,500 °C or at least about 1,000 °C and no more than about 1,500 °C), inclusive of all values and ranges therebetween. In some embodiments, the temperature in the pressure vessel during hot isostatic pressing can be about 500 °C, about 750 °C, about 1,000 °C, about 1,250 °C, about 1,500 °C, about 1,750 °C, about 2,000 °C, about 2,250 °C, or about 2,500 °C.

[0088] In some embodiments, hot isostatic pressing can be carried out for a duration of between about 1 minute and about 15 hours, about 5 minutes and about 10 hours, about 10 minutes and about 9 hours, about 30 minutes and about 8 hours, about 1 hour and about 7 hours, about 1 hour and about 6 hours, about 1 hour and about 5 hours, about 1 hour and about 4 hours, about 1 hour and about 3 hours, about 1 hour and about 2 hours, about 1.5 hours and about 10 hours, about 2 hours and about 10 hours, about 3 hours and about 10 hours, about 4 hours and about 10 hours, about 5 hours and about 10 hours, or about 10 hours and about 15 hours. In some embodiments, hot isostatic pressing can be carried out for a duration of greater than about 1 minute, 5 minutes, 10 minutes, 30 minutes, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, or 15 hours, inclusive of all values and ranges therebetween. In some embodiments, hot isostatic pressing can be carried out for a duration of less than about 15 hours, 14 hours, 13 hours, 12 hours, 11 hours, 10 hours, 9 hours, 8 hours, 7 hours, 6 hours, 5 hours, 4 hours, 3 hours, 2 hours, 1 hour, 30 minutes, 10 minutes, 5 minutes, or 1 minute, inclusive of all values and ranges therebetween.

[0089] In some embodiments, the use of hot isostatic pressing may also improve the effective diffusion bonding of alloyed metals. In some embodiments, when using the nanocrystalline metal alloys described herein and in the‘325 publication, the‘381 application, and the‘383 application, hot isostatic pressing may be more effective than hot isostatic pressing of sintered articles formed from conventional metal powders. In particular, in some embodiments, the nanocrystalline metal powders described herein have less surface area and are therefore less reactive, which results in more dense packing and less porosity in the sintered article. In some embodiments, the nanocrystalline metal powders described herein can undergo the NMIM process using less binder, which may result in less defect propagation during debinding, sintering, and/or hot isostatic pressing. Without wishing to be bound by any particular theory, the hot isostatic pressing of sintered articles formed by NMIM of nanocrystalline metal powders can lead to a finished article that is denser, has fewer defects, has reduced asymmetric shrinkage during hot isostatic pressing, and/or has improved mechanical properties. [0090] In some embodiments, the sintered article formed according to the NMIM process described herein and using the NCM alloy systems described herein can exhibit increased hardness and/or fracture toughness relative to articles formed using conventional metal alloys and a conventional NMIM process.

[0091] All literature and similar material cited in this application, including, but not limited to, patents, patent applications, articles, books, treatises, and web pages, regardless of the format of such literature and similar materials, are expressly incorporated by reference in their entirety. In the event that one or more of the incorporated literature and similar materials differs from or contradicts this application, including but not limited to defined terms, term usage, described techniques, or the like, this application controls.

[0092] While the present teachings have been described in conjunction with various embodiments and examples, it is not intended that the present teachings be limited to such embodiments or examples. On the contrary, the present teachings encompass various alternatives, modifications, and equivalents, as will be appreciated by those of skill in the art.

[0093] While various inventive embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the function and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the inventive embodiments described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the inventive teachings is/are used. Those skilled in the art will recognize many equivalents to the specific inventive embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto; inventive embodiments may be practiced otherwise than as specifically described and claimed. Inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the inventive scope of the present disclosure. [0094] All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and/or ordinary meanings of the defined terms.

[0095] The indefinite articles“a” and“an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean“at least one.” Any ranges cited herein are inclusive.

[0096] The phrase“and/or,” as used herein in the specification and in the claims, should be understood to mean“either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with“and/or” should be construed in the same fashion, i.e.,“one or more” of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the“and/or” clause, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, a reference to“A and/or B”, when used in conjunction with open-ended language such as“comprising” may refer, in some embodiments, to A only (optionally including elements other than B); in some embodiments, to B only (optionally including elements other than A); in yet some embodiments, to both A and B (optionally including other elements); etc.

[0097] As used herein in the specification and in the claims,“or” should be understood to have the same meaning as“and/or” as defined above. For example, when separating items in a list,“or” or“and/or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as“only one of’ or“exactly one of,” or, when used in the claims,“consisting of,” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term“or” as used herein shall only be interpreted as indicating exclusive alternatives (i.e.“one or the other but not both”) when preceded by terms of exclusivity, such as“either,”“one of,”“only one of,” or “exactly one of.”“Consisting essentially of,” when used in the claims, shall have its ordinary meaning as used in the field of patent law.

[0098] As used herein in the specification and in the claims, the phrase“at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase“at least one” refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example,“at least one of A and B” (or, equivalently,“at least one of A or B,” or, equivalently“at least one of A and/or B”) may refer, in some embodiments, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in some embodiments, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet some embodiments, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc.

[0099] As used herein“at%” refers to atomic percent and“wt%” refers to weight percent. However, in certain embodiments when“at%” is utilized the values described may also describe“wt%.” For example, if“20 at%” is described in some embodiments, in other embodiments the same description may refer to“20 wt%.” As a result, all“at%” values should be understood to also refer to“wt%” in some instances, and all“wt%” values should be understood to refer to“at%” in some instances.

[0100] In certain embodiments when an alloy system is described as being“coarse” and/or“ultra-fine” and/or“nanostructured” and/or“nanocrystalline”, the system may also be described using any of the other terms in other embodiments. As a result, it should be understood that any alloy system described using one of these terms could also be described using any other similar term in some instances.

[0101] In the claims, as well as in the specification above, all transitional phrases such as“comprising,”“including,”“carrying,”“having,”“containing,”“involving,” “holding,” “composed of,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases“consisting of’ and“consisting essentially of’ shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03.

[0102] The claims should not be read as limited to the described order or elements unless stated to that effect. It should be understood that various changes in form and detail may be made by one of ordinary skill in the art without departing from the spirit and scope of the appended claims. All embodiments that come within the spirit and scope of the following claims and equivalents thereto are claimed.

Claims

1. A method for manufacturing a metal alloy article using metal injection molding, the method comprising:

mixing a plurality of nanocrystalline metal particles with a binder to form a molding feedstock;

transferring the molding feedstock to a mold to form a molded structure;

debinding the molded structure; and

sintering the molded structure to form the metal alloy article, the metal alloy article having a relative density of at least about 90 %.

2. The method of claim 1, wherein the molding feedstock comprises less than about 55 vol% of the nanocrystalline metal particles.

3. The method of claim 1, wherein the molding feedstock comprises less than about 52 vol% of the nanocrystalline metal particles.

4. The method of claim 1, wherein the molding feedstock comprises about 48 vol% to about 55 vol% of the nanocrystalline metal particles.

5. The method of claim 1, wherein the relative density of the metal alloy article is at least about 95%.

6. The method of claim 1, wherein the relative density of the metal alloy article is at least about 98%.

7. The method of claim 1, wherein the relative density of the metal alloy article is at least about 99%.

8. The method of claim 1, wherein the debinding includes at least one of thermal debinding, catalytic debinding, and chemical debinding.

9. The method of claim 1, further comprising:

pressing the metal alloy article in a pressure vessel.

10. The method of claim 9, wherein the pressing includes hot isostatic pressing.

11. The method of claim 1, wherein the nanocrystalline metal particles have a volume average grain size of less than about 100 nm.

12. A method for manufacturing a metal alloy article using metal injection molding, the method comprising:

mixing a plurality of nanocrystalline metal particles with a binder to form a molding feedstock, the molding feedstock comprising a weight fraction of the nanocrystalline metal particles;

transferring the molding feedstock to a mold to form a molded structure;

debinding the molded structure; and

sintering the molded structure to form the metal alloy article, the metal alloy article having a relative density,

wherein the ratio of the relative density to the weight fraction of the nanocrystalline metal particles is at least about 1.5: 1.

13. The method of claim 12, wherein the ratio of the relative density to the weight fraction of the nanocrystalline metal particles is at least about 1.75: 1.

14. The method of claim 12, wherein the ratio of the relative density to the weight fraction of the nanocrystalline metal particles is at least about 1.8: 1.

15. The method of claim 12, wherein the ratio of the relative density to the weight fraction of the nanocrystalline metal particles is at least about 1.85: 1.

16. The method of claim 12, wherein the ratio of the relative density to the weight fraction of the nanocrystalline metal particles is at least about 1.9: 1.

17. The method of claim 12, wherein the debinding includes at least one of thermal debinding, catalytic debinding, and chemical debinding.

18. The method of claim 12, further comprising: pressing the metal article in a pressure vessel.

19. The method of claim 14, wherein the pressing is hot isostatic pressing.

20. A method for manufacturing a metal alloy article, the method comprising:

mixing a plurality of nanocrystalline metal particles with a binder to form a molding feedstock, the molding feedstock having a solids loading rate of at least about 48 vol%;

transferring the molding feedstock to a mold to form a molded structure;

debinding the molded structure; and

sintering the molded structure to form the metal alloy article, the metal alloy article having a relative density of at least about 90%.

21. The method of claim 20, wherein the molded structure has a solids loading rate of between about 48 vol% and about 55 vol%.

22. The method of claim 21, wherein the molded structure has a solids loading rate of between about 50 vol% and about 55 vol%.

23. The method of claim 22, wherein the molded structure has a solids loading rate of between about 50 vol% and about 52 vol%.

24. The method of claim 20, wherein the relative density of the metal alloy article is at least about 95%.

25. The method of claim 20, wherein the relative density of the metal alloy article is at least about 98%.

26. The method of claim 20, wherein the relative density of the metal alloy article is at least about 99%.

27. The method of claim 20, wherein the debinding includes at least one of thermal debinding, catalytic debinding, and chemical debinding.

28. The method of claim 20, further comprising:

pressing the metal alloy article in a pressure vessel.

29. The method of claim 28, wherein the pressing is hot isostatic pressing.