CN114871445A

CN114871445A - Method for manufacturing nano-structure copper-based bimetal composite material through cold spraying solid additive

Info

Publication number: CN114871445A
Application number: CN202210515917.XA
Authority: CN
Inventors: 雒晓涛; 赵佰要; 李长久
Original assignee: Xian Jiaotong University
Current assignee: Xian Jiaotong University
Priority date: 2022-05-12
Filing date: 2022-05-12
Publication date: 2022-08-09
Anticipated expiration: 2042-05-12
Also published as: CN114871445B

Abstract

The invention discloses a method for manufacturing a copper-based bimetallic composite material with a nano structure by cold spraying solid additive, which comprises the following steps of firstly preparing mixed powder from Cu powder and metal powder which forms a mutual non-solid solution system with Cu according to a certain proportion, and carrying out mechanical alloying by high-energy ball milling equipment; secondly, a cold spraying process is adopted to prepare parts or revolved bodies with complex internal structures and shapes, and then the prefabricated parts are subjected to heat treatment in vacuum. The method provides a new method for additive manufacturing of the copper-based bimetallic part or the revolving body with the complex configuration and has the advantages of low internal porosity of the material, compact structure, nanostructure, low preparation cost, simple process flow, high deposition speed and short production period, and solves the problem that the complex-configuration part with the nanostructure cannot be obtained by the existing preparation process.

Description

Method for manufacturing nano-structure copper-based bimetal composite material through cold spraying solid additive

Technical Field

The invention belongs to the field of additive manufacturing, and particularly relates to a method for manufacturing a copper-based bimetallic composite material with a nano structure by cold spraying solid additive.

Background

Currently, the nano-structured materials composed of systems without mutual solid solution are receiving wide attention due to the structural particularity, and are the main direction for developing novel anti-radiation materials. The nano-structure material represented by a nano-multilayer film has the advantages that the thickness of a single metal layer is reduced to a nano size, so that the interface between heterogeneous metals is obviously increased, the heterogeneous metal phase boundary with high volume fraction can be used as an 'effective absorption trap' of irradiation induced point defects, the healing of interstitial atoms and vacancies is promoted, the aggregation of irradiation defects in the material is reduced, and the excellent irradiation resistance is realized. The solid solubility between the components in the mutually immiscible system is very low, and the components are not easy to diffuse or alloy when being irradiated and heated, so that the reactor has extremely high stability, and has great potential in the application of the next generation of reactor materials.

However, the nano-multilayer films also have significant disadvantages: only can be made into a film or a plate, and the prior art lacks a method for preparing parts with complex configurations, thereby severely limiting the application of the material in industry. The current mainstream preparation process of the nano multilayer film is a magnetron sputtering technology and an accumulative pack rolling technology, so that the preparation process is complicated, the efficiency is low, the size and the shape of a product are limited, and subsequent machining cannot be carried out to obtain parts.

The metal parts with target configuration can be rapidly prepared by the additive manufacturing technology represented by high-energy beams such as laser, plasma, electric arc and the like. However, in the conventional additive manufacturing techniques, there are melting and cooling processes, and due to different melting points and densities of metal components of non-solid solution systems, not only the prepared material lacks a nanoscale interface, but also a layered alternating structure similar to a multilayer film cannot be obtained, even if nanoscale heterogeneous metal alternative distribution characteristics exist in the initial powder raw material, after the powder is melted, due to immiscible metals and large density difference, separation of the two metals occurs, and it is difficult to obtain a two-phase alternating structure.

Mechanical alloying is an effective method for preparing nano-structure composite powder, can enable the powder to have an obvious alternate distribution structure, and is expected to obtain the nano-structure heterogeneous metal alternate distribution structure under the condition of optimized mechanical alloying parameters, wherein the size of a metal phase is gradually reduced and the size of metal grains is refined along with continuous welding and crushing of the heterogeneous metal powder in the mechanical alloying process. When the cold welding and the fracture in the powder reach dynamic balance along with the increase of the ball milling time, the size of the particle diameter of the obtained powder is stable and unchanged, and the requirement of cold spraying on the particle diameter of the powder is met. As an additive manufacturing technology which is rapidly developed in recent years, cold spraying has been used to prepare parts with complex configurations due to its characteristics of low-temperature solid deposition, unlimited product shape, no phase change and no grain growth during spraying, and the like.

The feature of cold spray low temperature solid state deposition can implant nanostructures in a powder into a component, which provides the possibility for additive manufacturing of nanostructured materials. However, the existing additive manufacturing method still cannot obtain a composite material which consists of immiscible system materials and has a heterogeneous metal phase interface with a nano structure inside.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide a method for manufacturing a copper-based bimetallic composite material with a nano structure by cold spraying solid additive, which can solve the technical problem that the composite material which consists of immiscible system materials and has a heterogeneous metal phase interface with a nano structure in the interior cannot be obtained by the existing preparation process.

In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose:

the invention discloses a method for manufacturing a copper-based bimetallic composite material with a nano structure by cold spraying solid additive, which comprises the following steps:

step one, mixing Cu powder and metal powder which forms a system without solid solution with Cu, and then carrying out mechanical alloying treatment under the protection of inert gas to prepare alloy powder;

secondly, spraying and preparing parts with complex internal structures and shapes by adopting a cold spraying process and taking the alloy powder prepared in the first step as a spraying raw material;

and step three, performing heat treatment on the prefabricated parts with complex internal structures and shapes under vacuum at the temperature of 200-600 ℃ for 2 hours to crystallize the amorphous phase in the sediment and eliminate the residual stress in the sediment to prepare the copper-based bimetallic composite material with the nano structure.

Preferably, in the step one, the metal powder which is not in a solid solution system with Cu is selected from one or more of Cu-Ta, Cu-W and Cu-Nb.

Preferably, in the first step, the volume ratio of the Cu powder to the metal powder of the immiscible system of Cu composition is 1: (0.25-4).

Preferably, in the step one, the Cu powder and the metal powder which forms a system without mutual solid solution with Cu are both spherical or irregular in shape, the particle size range is 0.05-80 μm, and the purity is more than or equal to 99.90%.

Preferably, in the step one, the mechanical alloying treatment is ball milling treatment, and the ball milling conditions are as follows: 150-300 r/min, the ball material ratio is (10-20): 1, the time is 16-48 h; the size of the grinding ball is one or more of 6mm, 8mm and 10 mm; the inert protective gas is argon or nitrogen.

Preferably, the granularity of the alloy powder prepared in the step one is 10-50 microns, the sphericity is good, heterogeneous metals in the alloy powder are alternately and uniformly distributed, the size of each metal is 5-100 nm, and the metal phase is crystalline or amorphous.

Preferably, in the second step, the accelerating gas used in the cold spraying is nitrogen or helium, the gas temperature is 300-700 ℃, the gas pressure is 2.0-5.0 MPa, the spraying distance is 15-30 mm, and the powder feeding speed is 20-150 g/min.

Preferably, in the second step, the part with the target size configuration can be prepared by adjusting the posture and the designed traveling path of the spray gun.

Preferably, in the second step, the porosity of the part with a complex internal structure and shape in the cold spraying state is less than 0.5%, the oxygen content is less than 0.2%, heterogeneous metals in the deposition body are alternately and uniformly distributed, the size of each metal is between 5 and 100nm, and the metal phase is crystalline or amorphous.

Preferably, in the third step, the amorphous phase in the deposit is crystallized after the heat treatment, the plasticity is improved, and the size of the metal phase in the deposit is not increased.

Compared with the prior art, the invention has the following beneficial effects:

the invention discloses a method for manufacturing a copper-based bimetallic composite material with a nano structure by cold spraying solid additive, which comprises the following steps of firstly preparing mixed powder from Cu powder and metal powder which forms a mutual non-solid solution system with Cu according to a certain proportion, and carrying out mechanical alloying by high-energy ball milling equipment; secondly, a cold spraying process is adopted to prepare parts or revolved bodies with complex internal structures and shapes, and then the prefabricated parts are subjected to heat treatment in vacuum. The process has the advantages that:

1. the copper-based bimetal is not mutually solid-dissolved, and no intermetallic compound or intermediate phase exists between the copper-based bimetal and the copper-based bimetal, so that the copper-based bimetal has good radiation resistance and thermal stability;

2. the nano-structure composite powder after mechanical alloying has the advantages of spheroidal shape, good sphericity and fluidity and easy powder feeding; the particle size distribution is uniform, and the particle size meets the requirements of a cold spraying process on powder;

3. the copper-based bimetallic composite material with the nano structure is manufactured by cold spraying solid additive, has compact structure and low porosity and has the nano structure; residual compressive stress exists in the composite material, so that the thick part can be prepared; the machining precision can be improved and the mechanical property can be improved through subsequent machining and heat treatment;

4. the invention can be used for preparing nano-structure parts and revolution bodies with complex configurations, and a large number of phase interfaces exist in the parts and the revolution bodies, and the grain size is nano-scale.

5. The copper-based bimetallic composite material with the nano structure is manufactured by cold spraying solid additive, so that the preparation cost is low, and the powder utilization rate is high; the process flow is simple, and complex and tedious operations are not needed; the deposition speed is high, the production period is short, and convenience and rapidness are realized; parts of any geometry can be made to meet the requirements of various parts.

Drawings

FIG. 1 is a graph of the morphology and particle size distribution of two materials involved in the practice of the present invention; wherein a is Cu powder; b is Ta powder, c is the result of particle size distribution;

FIG. 2 is a scanning electron micrograph of the morphology and the cross section of the powder after mechanical alloying in example 1; wherein a is a topography; b is a section scanning photo;

FIG. 3 is a scanning electron micrograph of a cross section of the as-sprayed composite material of example 1;

FIG. 4 is a transmission electron micrograph of a cross section and a selected area electron diffraction pattern of the as-sprayed composite material of example 1; wherein, a is a bright field image photo, b is a selected area electron diffraction pattern;

FIG. 5 is a schematic view of the nano-W powder of example 2;

FIG. 6 is a scanning electron micrograph of the morphology and the cross section of the powder after mechanical alloying and the particle size distribution of the composite powder in example 2; wherein a is morphology; b is a section scanning electron microscope photograph; c is the particle size distribution of the composite powder;

FIG. 7 is a scanning electron micrograph of a cross section of the as-sprayed composite material of example 2.

Detailed Description

In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

The invention is described in further detail below with reference to the accompanying drawings:

the invention discloses a method for manufacturing a copper-based bimetallic composite material with a nano structure by cold spraying solid additive, which adopts the following scheme:

firstly, Cu powder and another metal powder which is not solid-dissolved with each other are adopted as raw materials, and are mechanically mixed according to a certain proportion and then are mechanically alloyed under the protection of inert gas, so that composite powder with good sphericity and granularity size of 10-50 mu m is obtained, bimetallic components in the powder are alternately distributed, the size of each metal component reaches the nanometer scale, and a large number of heterogeneous metal interfaces exist; secondly, under the optimized cold spraying process parameters, the preparation of the complex-configuration parts is realized by adjusting the posture of the spray gun and designing a traveling path; and finally, the machining precision of the component is improved and the mechanical property is improved through subsequent mechanical machining and heat treatment. The invention provides a new method for additive manufacturing of a copper-based bimetallic part or a revolving body with a complex-structured nano structure, and the copper-based bimetallic part or revolving body is low in internal porosity, compact in structure, low in preparation cost, simple in process flow, high in deposition speed and short in production period, and has a nano structure, so that the problem that the complex-structured part with the nano structure cannot be obtained by the existing preparation process is solved.

Example 1

Step one, as shown in figure 1, spherical Cu powder with the particle size of 10-50 microns and polygonal Ta powder with the particle size of 20-65 microns are mixed according to the volume ratio of 1:1 and then are placed into a vacuum ball milling tank together with a process control agent, and then high-purity argon gas with the pressure of about 0.2MPa is introduced. And placing the vacuum ball milling tank on a high-energy planetary ball mill, wherein the grinding balls are prepared according to the following formula: 3: 1, 6mm, 8mm and 10mm grinding balls distributed according to the weight ratio, wherein the ball material ratio is 10: 1, carrying out mechanical alloying reaction at a rotation speed of 250r/min, wherein the ball milling time is 32h, the process control agent is stearic acid, and the addition amount is 0.5 wt.%. And after the mechanical alloying reaction is finished, standing and cooling for 2 hours, and then taking out the powder sample.

As shown in a in figure 2, the surface of the composite powder after ball milling is observed by a scanning electron microscope photo, the shape is similar to a sphere, the flaky powder is not flat, the sphericity and the fluidity are good, and the particle size of the powder is uniform, and as seen from c in figure 1, the particle size ranges are less than 50 microns and more than 10 microns, so that the requirement of cold spraying on the particle size of the powder is met. As shown in b in fig. 2, from the observation of the cross-section of the composite powder after ball milling by scanning electron microscope, it can be seen that the powder is dense and has no pores inside, the layered thickness is smaller than the resolution of the scanning electron microscope, no obvious aggregation of two phases occurs, and the distribution is good.

And step two, taking the composite powder obtained in the step one as spraying powder, taking nitrogen as accelerating gas, and adjusting the posture of a spray gun and designing a traveling path to carry out cold spraying under the spraying conditions that the gas temperature is 700 ℃, the gas pressure is 5MPa and the spraying distance is 20 mm. As shown in FIG. 3, from the scanning electron micrograph of the cross section of the sprayed composite material, it can be seen that the internal pores are small and the powder deforms to a large extent during the spraying process. The composite material is further observed by using a transmission electron microscope, wherein a in fig. 4 is a bright field image mode, b in fig. 4 is a selected area electron diffraction pattern, a bright color area is Ta, a dark color area is Cu, heterogeneous metals in the material are alternately and uniformly distributed, the size of each metal is less than 50nm, and a metal phase is crystalline or amorphous. The joint surface scanning results show that the Cu phase and the Ta phase are dispersed and uniformly distributed, and the element content ratio is approximately equal to the initial powder ratio.

And step three, carrying out vacuum heat treatment on the composite material obtained in the step two. The heat treatment temperature is 650 ℃, the heat preservation time is 2 hours, and the furnace is cooled to the room temperature. After the heat treatment, the amorphous phase in the sediment body is crystallized, the plasticity is improved, the size of the metal phase in the sediment body is not increased, and the copper-based bimetal composite material with the nano structure is obtained.

Example 2

Step one, as shown in fig. 5, spherical Cu powder with the particle size of 10-50 μm and spherical W powder with the particle size of 50nm are mixed according to the volume ratio of 3:2 and then are put into a vacuum ball-milling tank together with a process control agent, and then high-purity argon gas with the pressure of about 0.2MPa is introduced. And placing the vacuum ball milling tank on a high-energy planetary ball mill, wherein the grinding balls are prepared according to the following formula: 3: 1, 6mm, 8mm and 10mm grinding balls distributed according to the weight ratio, wherein the ball material ratio is 10: 1, carrying out mechanical alloying reaction at a rotation speed of 250r/min, wherein the ball milling time is 32h, the process control agent is stearic acid, and the addition amount is 0.5 wt.%. And after the mechanical alloying reaction is finished, standing and cooling for 2 hours, and then taking out the powder sample.

As shown in a in fig. 6, as observed from the scanning electron microscope surface photograph of the ball-milled composite powder, the morphology is spheroidal, the flaky powder is not flat, the sphericity and the fluidity are good, and the particle size of the powder is uniform, and as seen from c in fig. 6, the particle size is mainly distributed between 30 μm and 70 μm, and the requirement of cold spraying on the particle size of the powder can be met after screening. As shown in b in fig. 6, when the cross-section of the composite powder after ball milling is observed by scanning electron microscope, it can be seen that the W powder (bright spots) inside the powder is uniformly dispersed, no agglomeration phenomenon occurs, and the powder is wrapped by the Cu powder with good ductility, and a large amount of Cu-W phase interfaces exist.

And step two, taking the composite powder obtained in the step one as spraying powder, taking nitrogen as accelerating gas, and adjusting the posture of a spray gun and designing a traveling path to carry out cold spraying under the spraying conditions that the gas temperature is 700 ℃, the gas pressure is 5MPa and the spraying distance is 20 mm. As shown in fig. 7, it can be seen from the scanning electron micrograph of the cross section of the as-sprayed composite material that a small number of unbound interfaces and pores between particles exist inside the composite material, and the nano-W powder is uniformly dispersed inside the material without significant agglomeration, so that the interface of the Cu and W phases with high volume fraction in the nano-scale in the powder is transplanted into the deposit.

And step three, carrying out vacuum heat treatment on the composite material obtained in the step two. The heat treatment temperature is 650 ℃, the heat preservation time is 2 hours, and the furnace is cooled to the room temperature. The un-bonded interfaces and pores in the material after heat treatment are obviously fewer, the density is improved, the nano structure is retained in the tissue, and the phase boundary with high volume fraction is obtained, so that the copper-based bimetal composite material with the nano structure is obtained.

In conclusion, the method combining mechanical alloying and cold spraying technology is adopted to obtain the copper-based bimetal composite powder with good sphericity and uniform particle size distribution and the nano-structure composite material with compact structure, fine internal crystal grain size and uniform two-phase distribution. The method has low preparation cost and high powder utilization rate; the process flow is simple, and complex and tedious operations are not needed; the deposition speed is high, the production period is short, and convenience and rapidness are realized; parts of any geometry can be made to meet the requirements of various parts.

The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A method for manufacturing a nano-structure copper-based bimetal composite material by cold spraying solid additive is characterized by comprising the following steps:

2. The cold spray solid state additive manufacturing method of a nanostructured copper-based bimetallic composite material according to claim 1, characterized in that in step one, the metal powder which is not in a solid solution system with Cu is selected from one or more of Cu-Ta, Cu-W and Cu-Nb.

3. The cold spray solid state additive manufacturing method of a nanostructured copper-based bimetallic composite material according to claim 1, characterized in that in step one, the volume ratio of the Cu powder to the metal powder of the Cu composition mutual non-solid solution system is 1: (0.25-4).

4. The cold spraying solid-state additive manufacturing method of the nano-structured copper-based bimetal composite material according to any one of claims 1 to 3, wherein in the first step, the Cu powder and the metal powder which forms a system without solid solution with Cu are both spherical or irregular in shape, the particle size range is 0.05-80 μm, and the purity is more than or equal to 99.90%.

5. The cold spray solid state additive manufacturing method of nanostructured copper-based bimetallic composite material according to claim 1, characterized in that in step one, the mechanical alloying treatment is ball milling treatment, and the ball milling conditions are as follows: 150-300 r/min, the ball material ratio is (10-20): 1, the time is 16-48 h; the size of the grinding ball is one or more of 6mm, 8mm and 10 mm; the inert protective gas is argon or nitrogen.

6. The method for manufacturing the copper-based bimetal composite material with the nano structure through the cold spraying solid additive according to claim 1, wherein the granularity of the alloy powder prepared in the step one is 10-50 μm, the sphericity is good, heterogeneous metals in the alloy powder are alternately and uniformly distributed, the size of each metal is 5-100 nm, and the metal phase is crystalline or amorphous.

7. The method for manufacturing the copper-based bimetal composite material with the nano structure through the cold spraying solid additive according to claim 1, wherein in the second step, the accelerating gas used in the cold spraying is nitrogen or helium, the gas temperature is 300-700 ℃, the gas pressure is 2.0-5.0 MPa, the spraying distance is 15-30 mm, and the powder feeding rate is 20-150 g/min.

8. The cold spray solid state additive manufacturing method of a nano-structured copper-based bimetal composite material according to claim 1, wherein in the second step, the part with the target dimensional configuration can be prepared by adjusting the posture and the designed traveling path of the spray gun.

9. The method for manufacturing the nano-structure copper-based bimetal composite material by cold spraying solid additive according to claim 1, wherein in the second step, the porosity of the part with the complex internal structure and shape in the cold spraying state is less than 0.5%, the oxygen content is less than 0.2%, heterogeneous metals in the deposition body are alternately and uniformly distributed, the size of each metal is between 5 and 100nm, and the metal phase is crystalline or amorphous.

10. The method for manufacturing the nanostructured copper-based bimetallic composite material by cold spray solid state additive manufacturing according to claim 1, characterized in that in step three, the amorphous phase in the deposit after heat treatment is crystallized, the plasticity is improved, and the size of the metal phase in the deposit does not grow.