CN115595510A

CN115595510A - Iron-manganese alloy with high work hardening capacity and preparation method and application thereof

Info

Publication number: CN115595510A
Application number: CN202211234913.0A
Authority: CN
Inventors: 吴宏; 刘佩峰; 刘波; 廖楚庭; 陈含蝶; 马雪茹
Original assignee: Central South University
Current assignee: Central South University
Priority date: 2022-10-10
Filing date: 2022-10-10
Publication date: 2023-01-13
Anticipated expiration: 2042-10-10
Also published as: CN115595510B

Abstract

The invention relates to a ferro-manganese alloy with high work hardening capacity and a preparation method and application thereof, belonging to the technical field of preparation of medical high-strength ferro-manganese alloy. In the ferro-manganese alloy, the content of Mn is 17.5-18.5wt%, the content of oxygen is less than or equal to 0.03wt%, and the balance is ferrum; the yield strength of the iron-manganese alloy is 220-300MPa, and the ultimate tensile strength is 870-998MPa. The ferro-manganese alloy takes Fe-Mn prealloy powder as a raw material; preparing a printing blank by adopting a 3D printing technology, and then carrying out heat treatment at 450-700 ℃ under a protective atmosphere; and obtaining a product, wherein the 3D printing parameters are as follows: the laser power is 200-220W, and the scanning speed is 680-720mm/s. The invention greatly improves the tensile strength of the product while ensuring that the product has certain yield strength, thereby achieving the purpose of improving the work hardening capacity of the product. The invention has simple and controllable components and strong processing and hardening capacity of products, and is convenient to be used as biomedical materials.

Description

Iron-manganese alloy with high work hardening capacity and preparation method and application thereof

Technical Field

The invention relates to a ferro-manganese alloy with high work hardening capacity and a preparation method and application thereof, belonging to the technical field of preparation of medical high-strength ferro-manganese alloy.

Background

Among the metal biomaterials, biodegradable alloys have received increasing attention in orthopedic implant applications over the last decade. It is a novel bioactive material, provides stable mechanical support for 3 to 6 months, and is completely absorbed by the human body in 1 to 2 years, without adverse pathophysiological and toxicological effects, which means that not only the cost of secondary operations is reduced, but also the pain of patients is alleviated. Among such medical metals, iron-based metals, particularly iron-manganese (Fe-Mn) based alloys, have excellent mechanical properties and workability, and the addition of Mn makes the Fe matrix more susceptible to corrosion within the solubility limit, increasing its degradation rate in physiological media; while Mn is an essential trace mineral required for normal brain and nerve function and formation of bone and connective tissue in humans (references: M.Aschner, T.R.Guilarte, J.S.Schneider, W.Zheng, man: recent advances in understandings transport and neurooxidability [ J ], toxicol.Appl.Pharmacol. [ J ].221 (2007) 131-147). Therefore, the excellent mechanical property, degradation property and biocompatibility make Fe-Mn alloy a candidate degradable bone implant material.

On the other hand, the bone substitute needs to be designed reasonably and individually for complex and various bone defect parts. Laser Powder Bed Fusion (LPBF) is a promising 3D printing technique that, when combined with Computer Aided Design (CAD), can produce complex layered structures with the advantages of high dimensional accuracy, short processing time, etc. Therefore, compared with the traditional manufacturing process, the method is an ideal preparation method of the bone implant material, and has great potential in the field of iron-based degradable metals. Since the degradation rate of the Fe-Mn alloy is greatly improved when Mn is more than 29.wt%, few reports about additive manufacturing of the Fe-Mn alloy concentrate on 30Mn and 35Mn series alloys, and a certain neurotoxicity is generated by high Mn content. According to the report of Hermawan et al, when the Mn content is less than or equal to 20wt.%, a dual-phase structure (i.e. gamma-fcc phase/alpha' -bcc phase + epsilon-hcp phase) is easier to form, the phase interface hinders shear deformation and improves mechanical properties, and the maximum tensile strength value of the dual-phase Fe-Mn alloy reported in the conventional powder metallurgy process is 702MPa (reference: H.Hermawan, D.Dube, D.Mantovani, degradable biological Materials: design and deformation of Fe-Mn alloys for use [ J ], journal of biological Materials Research Part A93A (1) (2008) 1-11). At the same time, the potential differences between the different phases eventually increase the tendency to corrode, as has been demonstrated in recent work in our group of subjects (ref: P Liu, H Wu et al, microtherapy, mechanical properties and correction results of additive-manufactured Fe-Mn alloys [ J ], materials Science & Engineering A852 (2022) 143585). In addition, the biphase Fe-Mn alloy is printed by using Fe and Mn element powder 3D in the earlier stage of the subject group (for example, patent 2021107262170); however, the ultimate tensile strength of the product obtained in the patent is only 855 to 858MPa.

Compared with the traditional process such as casting, powder metallurgy and the like, the LPBF has a finer microstructure and higher tensile strength due to extremely fast cooling speed. However, heat flow and temperature gradients opposite to the build direction can lead to microstructural inhomogeneities and extreme residual stresses, which undoubtedly lead to early mechanical failure and a reduction in plasticity. In view of the above facts, it is necessary to perform appropriate heat treatment on the printed sample to reduce residual stress and obtain a uniform texture. The prior Fe-Mn alloy heat treatment literature is very few and is limited to powder metallurgy. Dehestani et al prepared alloys by sintering FeMn mixed powders and studied the effect of heat treatment temperature on the texture and mechanical properties and found that more epsilon-martensite phases were precipitated after heat treatment than the original samples. However, the tensile strength of the alloy is not improved whether the heat treatment is carried out at 700 ℃ or 900 ℃ (references: mahdi Dehistani, kevin trunble, han Wang, haiyan Wang, lia A.Stanciu, effects of micro and waste treatment on mechanical properties and corrosion diagnosis of powder metallic supplied Fe-30Mn alloy J ], materials Science & Engineering A703 (2017) 214-226). There is currently no literature on heat treatment of LPBFed Fe-Mn alloys that reports that due to their unique microstructure, the microstructural changes induced in the L-PBF material after heat treatment are expected to be different from their sintered or cold rolled counterparts.

Meanwhile, until now, no reports on how to improve the work hardening capacity of the product while ensuring the yield strength of the product by taking the ferrosilicon-free manganese alloy with the Mn content of less than 20% as a research object are found.

Disclosure of Invention

On the basis of the patent 2021107262170, the invention further researches and explores the attempt of enhancing the mechanical property and the work hardening capacity of the product; the present invention is presented based on an attempted optimization scheme.

The invention relates to a ferro-manganese alloy with high work hardening capacity; in the ferro-manganese alloy, the content of Mn is 17.5-18.5wt%, the content of oxygen is less than or equal to 0.03wt%, and the balance is ferrum; the yield strength of the iron-manganese alloy is 220-300MPa, and the ultimate tensile strength is 870-998MPa. In the present invention, the yield strength and ultimate tensile strength were measured at room temperature.

In the present invention, work hardening ability of the specimen = ultimate tensile strength-yield strength; the greater the difference between ultimate tensile strength and yield strength, the higher the work hardening capacity.

The invention ensures that the product has certain yield strength, namely 220-300MPa, and is used for providing enough mechanical support when being implanted; the invention improves the ultimate tensile strength of the product under the condition of ensuring the yield strength, thereby achieving the purpose of improving the work hardening capacity of the product. The stronger the work hardening ability of the product, the stronger the ability to adapt to deformation, thereby having advantages in both implantation stability and safety.

The invention relates to a ferro-manganese alloy with high work hardening capacity; the iron-manganese alloy takes Fe-Mn prealloying powder as a raw material; preparing a printing blank by adopting a 3D printing technology, and then carrying out heat treatment at 450-700 ℃ under a protective atmosphere; and obtaining a product, wherein the 3D printing parameters are as follows: the laser power is 200-220W, and the scanning speed is 680-720mm/s;

the structure of the printing blank mainly comprises acicular martensite (alpha'), cellular subgrain and columnar subgrain;

compared with a printing blank, the cellular subgrade and the columnar subgrade of the finished product are still stable, the size is not changed, and the finer acicular alpha' martensite is uniformly distributed in the matrix. The phase volume fraction of epsilon martensite in the finished product (65.16 vol.%) is greater than the phase volume fraction of epsilon martensite in the print blank (62.09 vol.%) compared to the print blank.

After optimization, the ferro-manganese alloy with high work hardening capacity is disclosed by the invention; after heat treatment, the product has the yield strength of 294-296MPa, the ultimate tensile strength of 995-997MPa and the elongation at break of 16.2-16.3 percent. Compare in printing the base, it all promotes on yield strength, ultimate tensile strength and elongation at break, more importantly: the work hardening capacity of the printing blank is further improved on the basis of the printing blank.

The invention relates to a preparation method of a ferro-manganese alloy with high work hardening capacity, which is prepared by matching 3D printing and heat treatment; the method specifically comprises the following steps:

taking Fe-Mn prealloying powder as a raw material; preparing a printing blank by adopting a 3D printing technology, and then carrying out heat treatment at 450-700 ℃ under a protective atmosphere; so as to obtain the product of the method,

in the Fe-Mn prealloying powder, the content of Mn is 18-18.5wt%, the content of oxygen is less than or equal to 0.03wt%, and the balance is iron;

the parameters for 3D printing are: the laser power is 200-220W, and the scanning speed is 680-720mm/s.

The tensile strength of the product is more than or equal to 884MPa.

Preferably, the method for preparing the high-strength ferro-manganese alloy by adopting the combination of 3D printing and heat treatment has the advantage that the particle size of the Fe-Mn prealloying powder is 15-53 mu m.

In industrial application, the Fe-Mn prealloyed powder is spherical Fe-Mn prealloyed powder prepared by a gas atomization method.

Preferably, the invention relates to a preparation method of ferro-manganese alloy with high work hardening capacity; the parameters for 3D printing are: the laser power was 210W and the scanning speed was 700mm/s.

Preferably, the invention relates to a preparation method of ferro-manganese alloy with high work hardening capacity; in 3D printing, the scanning pitch was 80 μm and the layer thickness was 30 μm.

Preferably, the invention relates to a preparation method of ferro-manganese alloy with high work hardening capacity; the pre-alloyed powder consists essentially of an fcc austenite phase (γ) and an hcp martensite phase (ε), while the print blank consists essentially of an hcp martensite phase and a bcc martensite phase.

Preferably, the invention relates to a preparation method of the ferro-manganese alloy with high work hardening capacity; the texture of the print blank is mainly composed of acicular martensite, cellular subgrains and columnar subgrains.

Preferably, the invention relates to a preparation method of ferro-manganese alloy with high work hardening capacity; columnar subgrains will grow along the direction of heat flow.

Preferably, the invention relates to a preparation method of the ferro-manganese alloy with high work hardening capacity; the heat treatment temperature is 645-655 ℃, the heat preservation time is 80-100min, and the cooling mode is furnace cooling.

Preferably, the invention relates to a preparation method of ferro-manganese alloy with high work hardening capacity; after heat treatment, cellular and columnar subgrains remain stable and unchanged in size compared to the print blank, but finer acicular martensite is uniformly distributed in the matrix. The phase volume fraction of epsilon martensite in the finished product (65.16 vol.%) is greater than the phase volume fraction of epsilon martensite in the print blank (62.09 vol.%) compared to the print blank.

Preferably, the invention relates to a preparation method of the ferro-manganese alloy with high work hardening capacity; after heat treatment, the product has stronger work hardening capacity than a printing blank, and the mechanical property is greatly improved.

After optimization, the yield strength of the printing blank is 205-207MPa, the ultimate tensile strength is 883-885MPa, and the elongation at break is 15.8-15.85%.

After optimization, the yield strength of the product after heat treatment is 294-296MPa, the ultimate tensile strength is 995-997MPa, and the elongation at break is 16.2-16.3%. In the process of the invention, the heat treatment temperature is 645-655 ℃, the holding time is 80-100min, and the yield strength, the ultimate tensile strength and the elongation at break of the product are all improved (relative to a printing blank) when the product is cooled along with a furnace, which is greatly beyond the expectation at that time.

After optimization, the product after heat treatment is fractured, and the fracture mode is ductile fracture.

The designed and prepared ferro-manganese alloy with high work hardening capacity can be applied to biological implant materials.

Principles and advantages

The invention firstly tries to improve the mechanical property of the product and the work hardening capacity of the product by adopting a mode of combining 3D printing and heat treatment on the Fe-Mn alloy, and utilizes the principle that the Mn content obviously influences the stacking fault energy (the stacking fault energy is lower than 20mJ/m when Mn is less than or equal to 18 wt.%) ² And the transformation induced plasticity (TRIP) effect and the twinning induced plasticity (TWIP) effect are easy to simultaneously occur), and the Fe-18Mn alloy (nominal component) is successfully prepared by combining the 3D printing technology. The extremely fast cooling speed of the material generates non-equilibrium phase transformation in the matrix, and finally forms an epsilon and alpha' dual-phase martensite structure. While the product is uniformly distributed with epsilon and alpha' phases under optimized heat treatment conditions, in addition to the TWIP and TRIP effects providing significant work hardening, the alternating epsilon (hard phase) and alpha (soft phase) distribution provides back stress reinforcement providing additional work hardening capacity (in the present invention work hardening capacity = ultimate tensile strength-yield strength; the greater the difference between ultimate tensile strength and yield strength, the higher the work hardening capacity). Therefore, 3D printing technology is compatible with subsequent heat treatment on the basis of the previous workAnd finally, the Fe-18Mn alloy with excellent work hardening capacity is obtained, and the ultimate tensile strength is obviously improved. The invention provides a product with excellent work hardening capacity, which has the advantages that: when the implant is implanted into a human body, the implant has good fatigue performance while providing enough mechanical support and adapts to deformation caused by cyclic loading, so that the stability and safety of the implant can be better ensured due to high work hardening capacity.

Drawings

FIG. 1 shows the densification and 5 under different laser process parameters (corresponding to the bulk energy density) in example 1 ^# 、11 ^# 、17 ^# Representative polished surface topography of the sample (corresponding to low, medium, and high volumetric energy densities, respectively);

FIG. 2 is an XRD pattern of the raw materials used in examples 1, 2, 3 and comparative examples 1, 2, 3, 4 and the resulting products;

FIG. 3 is an SEM micrograph of corresponding products of examples 1, 2, 3 and comparative example 1;

FIG. 4 is a graph of tensile engineering stress strain for the corresponding products of examples 1, 2, 3 and comparative example 1;

FIG. 5 is a tensile fracture morphology of the products obtained in examples 1, 2 and comparative example 1;

FIG. 6 is a tensile fracture morphology plot of the products obtained in comparative examples 2, 3, 4.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings.

Example 1

The Fe-Mn alloy rod was atomized to obtain spherical Fe-Mn prealloyed powder for use (particle size: 15-53 μm, composition shown in Table 1). Adopt laser powder bed melting equipment (LPBF, provided by Hua dao high-tech limited of Hunan, FARSOON 271M) to scan the alloy powder layer by layer (the oxygen content in the forming bin is less than 100 ppm), the laser power setting interval is: 120-270W, the scanning speed setting interval is as follows: 600-800mm/s, all samples scan at a pitch of 80 μm and a layer thickness of 30 μm; the numbers of different laser process parameters are shown in table 1, and finally, a scanning direction stretching piece with the thickness of 1.5mm and a cube with the length, width and height of 10mm are printed for subsequent performance analysis.

TABLE 1

Effects of the implementation

1. Volume energy Density (VED, J/mm) ³ ) The most reflective of the energy input during printing is calculated by the formula VED = P/v × h × t (P stands for laser power, v stands for scanning speed, h stands for scanning pitch, and t stands for layer thickness). Fig. 1 shows the density and the corresponding polished surface topography under different laser process parameters (corresponding volumetric energy density), the density being measured by archimedes drainage. It can be seen that under low energy density, the compactness ranges from 97.05% to 98.69%, and in combination with the results of fig. 1a and table 2, many unfused holes appear on the polished surface, and due to insufficient energy input, a large amount of Mn element is burned off, and the mass percentage is only about 14 wt%; similarly, at too high an energy density, in the range of 98.13% to 98.40% densification, combined with the results of fig. 1c and table 2, at too high an energy input, polishing showed the formation of many spherical pores, which were caused by Mn sublimation, and the final Mn content was only 15wt.%. Relatively speaking, at moderate energy input (corresponding to 7) ^# To 12 ^# Sample) the compactness of the sample can reach more than 99.2 percent, particularly aiming at 11 ^# The compactness of the sample, namely the sample with the laser process parameter of 210W and 700mm/s reaches 99.94 percent. Combining the results of fig. 1b and table 2, at which the sample surface was almost fully dense with no significant pore defects, the Mn content measured under the laser parameters was 17.8wt.%, which was substantially close to the Mn content of the original powder (18.3 wt.%). In summary, the optimal laser process parameters of the Fe-Mn alloy sample are as follows: laser power 210W, scanning speed 700mm/s (named As-build sample).

TABLE 2

Sample(s)	Mn(wt.％)	O(wt.％)	Fe(wt.％)
				Fe-18Mn prealloyed powder	18.3	0.02	Bal.
2 ^#	14.4	0.07	Bal.
				5 ^#	14.2	0.09	Bal.
11 ^#	17.8	0.03	Bal.
				13 ^#	15.2	0.07	Bal.
17 ^#	14.8	0.13	Bal.

2. As can be seen from the XRD results in FIG. 2, there is some difference between the As-build sample and the prealloyed powder. The prealloyed powder consisted primarily of an fcc austenite phase (γ) and an hcp martensite phase (ε), while the As-build sample consisted primarily of an hcp martensite phase and a bcc martensite phase (α'), with a volume fraction of ε phase of 62.09vol.% As measured by electron back-scattering diffraction equipment (FE-SEM, quanta 250FEG, america). The alloy undergoes a very fast rate of cooling after melting, which typically results in an unbalanced phase transition, with the gamma → epsilon phase transition occurring at 12-30 wt.% Mn and the epsilon → alpha' phase transition occurring at 12-18 wt.%. After being melted, the Fe-Mn alloy rod is dispersed into fine liquid drops through high-speed airflow, and FeMn prealloy powder is obtained through rapid cooling, so that a part of high-temperature gamma austenite phase is unstable and can be converted into an epsilon martensite phase, and the Mn content of an As-build sample is lower than 18wt.%, so that after the high-temperature austenite phase is formed in the LPBF process, the phase transformation of gamma → epsilon → alpha' is generated through rapid cooling, and a part of the epsilon martensite phase is reserved, so that the main peak strength of the martensite is reduced compared with that of the prealloy powder.

3. Scanning surface microstructure (SEM) of As-build sample is shown in FIG. 3, wherein the structure is mainly composed of acicular martensite, cellular subgrain and columnar subgrain, the phase interface of epsilon and alpha' is clearly observed at low magnification, and cellular subgrain and columnar subgrain with different orientations are formed when observed at high magnification, which is mainly caused by uneven temperature gradient distribution and different growth modes of the subgrain, and the columnar subgrain generally grows along the opposite direction of heat flow.

4. The tensile engineering stress strain curve of As-build samples is shown in FIG. 4, due to the lower stacking fault energy (< 20 mJ/m) at Mn content around 18wt.% (Mn content) ² ) Besides dislocation glide, twinning and phase transformation occur during deformation, so that significant work hardening occurs during drawing. Compared with the original yield strength, the ultimate tensile strength is greatly improved. Table 3 lists the mechanical property data of As-build samples, their tensile strength (884 MPa) and fracture elongationThe elongation (15.81%) is higher than that of the two-phase Fe-Mn alloy prepared by the current powder metallurgy method. In inventive example 1, the work hardening capability of the obtained As-build sample was already relatively high.

TABLE 3

5. FIG. 5 shows tensile fracture morphology of As-build samples, where large areas of cleavage fracture and randomly distributed dimples were found, both from macroscopic and macroscopic observations. Since the epsilon and alpha 'phase boundaries are evident in FIG. 3, the hard epsilon phase leads to a cleavage fracture mode, while the alpha' phase leads to a ductile fracture mode, thus resulting in an uneven fracture surface in multiple fracture modes.

Example 2

Scanning the ferro-manganese prealloy powder layer by adopting LPBF equipment, wherein the laser power is 210W, the scanning speed is 700mm/s, the scanning interval is 80 mu m, the scanning layer thickness is 30 mu m, and a scanning direction stretching piece with the thickness of 1.5mm and a cube with the length, width and height of 10mm are printed. And sealing the tensile piece and the cube in a quartz tube filled with argon, immediately putting the quartz tube into a muffle furnace for heat treatment, wherein the heating rate is 10 ℃/min, the temperature is 650 ℃, the heat preservation time is 90min, the cooling mode is furnace cooling, and the tensile piece and the cube are named as HT650 samples and are subjected to subsequent performance analysis.

Effects of the implementation

1. The XRD results for the HT650 sample are shown in fig. 2, and also consist of an epsilon martensite phase and an alpha ' martensite phase, the alpha ' peak intensity is reduced and the epsilon peak intensity is increased compared to the As-build sample, which means that the epsilon phase volume fraction is increased and more easily identified, and the epsilon phase volume fraction is 65.16vol.% As measured by electron back scattering diffraction equipment (ebsd), which is mainly related to the alpha ' → epsilon reverse phase transformation that occurs under heat treatment conditions, when the cooling rate of the furnace cooling is slower and more epsilon martensite is retained.

2. As can be seen from the SEM results of fig. 3, under the 650 ℃ heat treatment condition (low temperature annealing), the cellular and columnar subgrains are still stable and the size is not changed. Unlike the As-build samples, the finer acicular α' martensite is uniformly distributed in the matrix.

3. The tensile engineering stress strain curve of HT650 is shown in FIG. 4, and is higher than the As-build sample in either yield strength (295 MPa), tensile strength (996 MPa) or elongation at break (16.28%). Quantitative results of the HT650 mechanical properties are listed in table 4, since the HT650 samples have a slightly higher volume fraction of epsilon phase than the As-build samples, in addition to the enhanced deformation mechanism described in example 1, back stress (HDI) is generated in the alternating soft and hard regions due to the different degrees of softness and hardness of epsilon phase and alpha' phase and a more uniform distribution of texture, the interaction between back stress and positive stress, more mobile dislocations are built up at the soft and hard interface, thus creating additional work hardening. In summary, HT650 has a stronger work hardening capacity than the As-build specimens, while the mechanical properties are also the best of all heat treated specimens. In all the explorations, the work hardening capacity of the product after the heat treatment of the example 2 is further improved on the basis of the As-build sample. This increase is also only reflected in this embodiment.

TABLE 4

4. Fig. 5 shows the tensile fracture morphology of the HT650 sample, and it can be seen that the entire fracture surface is very flat, and many fine dimples can be seen at high multiples, indicating that the main fracture mode is ductile fracture under uniform tissue distribution, which also verifies that the elongation at fracture is improved by heat treatment at 650 ℃.

Example 3

Scanning the ferro-manganese prealloy powder layer by adopting LPBF equipment, wherein the laser power is 210W, the scanning speed is 700mm/s, the scanning interval is 80 mu m, the scanning layer thickness is 30 mu m, and a scanning direction stretching piece with the thickness of 1.5mm and a cube with the length, width and height of 10mm are printed. And sealing the tensile piece and the cube in a quartz tube filled with argon, immediately putting the quartz tube into a muffle furnace for heat treatment, wherein the heating rate is 10 ℃/min, the temperature is 850 ℃, the heat preservation time is 90min, the cooling mode is furnace cooling, and the tensile piece and the cube are named as HT850 samples and are subjected to subsequent performance analysis.

Effects of the implementation

1. The XRD results for the HT850 sample are shown in fig. 2, also consisting of an epsilon martensite phase and an alpha 'martensite phase, with a slightly reduced alpha' peak intensity compared to HT650, with a volume fraction of epsilon phase of 69.44vol.%, measured by ebsd.

2. From the SEM results of fig. 3, it can be seen that, in contrast to the texture morphology of the products obtained in examples 1 and 2, the cellular and columnar subgrains of the HT850 sample have completely disappeared, and instead of having a cross distribution of lath-like martensite, the lath-like martensite width is larger than that of the original sample. Outside the lath-shaped area, the martensite is alpha'.

3. The tensile engineering stress-strain curve of HT850 is shown in FIG. 4, and compared with HT650 sample, the strength plasticity is reduced (tensile strength 889MPa, elongation at break 11.61%), while compared with As-build sample, the strength is slightly improved, and the elongation at break is significantly reduced, and the corresponding mechanical property quantitative results are listed in Table 5. Although the texture distribution is more uniform, the coarser, denser lath epsilon martensite makes the overall strength inferior to that of the HT650 sample, while the stress concentration area increases, resulting in a decrease in the plasticity of the material.

TABLE 5

Comparative example 1

Scanning the ferro-manganese prealloy powder layer by adopting LPBF equipment, wherein the laser power is 210W, the scanning speed is 700mm/s, the scanning interval is 80 mu m, the scanning layer thickness is 30 mu m, and a scanning direction stretching piece with the thickness of 1.5mm and a cube with the length, width and height of 10mm are printed. And sealing the tensile piece and the cube in a quartz tube filled with argon, immediately putting the quartz tube into a muffle furnace for heat treatment, wherein the heating rate is 10 ℃/min, the temperature is 1050 ℃, the heat preservation time is 90min, the cooling mode is furnace cooling, and the tensile piece and the cube are named as HT1050 samples and are subjected to subsequent performance analysis.

Effects of the implementation

1. From the XRD results of fig. 2, it can be seen that the HT1050 sample is also composed of epsilon martensite phase and alpha' martensite phase, and the phase volume fractions are not different from those of the HT850 sample.

2. From the SEM high power morphology of fig. 3, it can be seen that HT1050 samples also cross-distributed lath-like epsilon martensite, but their widths continue to increase, and alpha' martensite is present outside the lath-like regions.

3. The tensile engineering stress strain curve of HT1050 is shown in figure 4, where the strength plasticity is reduced (636 MPa tensile strength, 7.17% elongation at break) compared to all samples, and the corresponding quantitative results are listed in table 6, where the mechanical properties of the samples are the worst, which is related to the dense epsilon martensite distribution with increased thickness.

TABLE 6

4. Figure 5 shows the tensile fracture morphology of the HT1050 sample, which demonstrates the poor plasticity of the HT1050 sample, as seen at low magnification, although the entire fracture surface is relatively flat, but instead the entire surface cleavage fractures with few pits present.

Comparative example 2

Scanning the ferro-manganese prealloy powder layer by adopting LPBF equipment, wherein the laser power is 210W, the scanning speed is 700mm/s, the scanning interval is 80 mu m, the scanning layer thickness is 30 mu m, and a scanning direction stretching piece with the thickness of 1.5mm and a cube with the length, width and height of 10mm are printed. And sealing the tensile member and the cube in a quartz tube filled with argon, immediately putting the quartz tube into a muffle furnace for heat treatment, wherein the heating rate is 10 ℃/min, the temperature is 450 ℃, the heat preservation time is 90min, the cooling mode is furnace cooling, and the tensile member and the cube are named as HT450 samples and are subjected to subsequent performance analysis.

Effects of the implementation

1. From the XRD results of fig. 2, it is seen that the HT450 sample is also composed of epsilon martensite phase and alpha 'martensite phase, and epsilon peak intensity is reduced compared to the HT650 sample because alpha' → epsilon reverse phase transformation is incomplete due to the reduction of heat treatment temperature.

2. Table 7 lists the mechanical property data for HT450 samples, with a 72MPa reduction in yield strength over HT650, a 86MPa reduction in ultimate tensile strength over HT650, and a lower elongation at break (13.45%) than for As-build and HT650 samples.

TABLE 7

3. From the tensile fracture morphology of FIG. 6, HT450 is mainly a mixed mode of ductile fracture and cleavage fracture, with a relatively uneven fracture surface.

Comparative example 3

Other conditions were the same as in example 2; the difference lies in that: the heat treatment temperature was 550 ℃ and was designated as HT550 sample. The XRD results obtained are shown in FIG. 2 and are not significantly different from those of HT450 sample. The tensile test results in 251MPa, 912MPa and 15.17% yield strength, ultimate tensile strength and elongation at break, respectively, and although the strength and plasticity performance is excellent, the yield strength, ultimate tensile strength and elongation at break are still lower than those of HT650 samples, which is not the optimal heat treatment parameter. The fracture morphology in fig. 6 shows that HT550 samples still have an uneven cleavage fracture plane.

Comparative example 4

Other conditions were the same as in example 2; the difference lies in that: the heat treatment temperature was 750 ℃ and was designated as HT750 sample. The XRD results obtained are shown in FIG. 2 and are not significantly different from those of the HT450 sample. The yield strength, the ultimate tensile strength and the elongation at break of the alloy are 269MPa, 871MPa and 13.71% respectively, the mechanical properties of the alloy are lower than those of an As-build sample and an HT650 sample, and the alloy is not the optimal heat treatment parameter. From the tensile fracture morphology of fig. 6, the fracture mode is still dominated by cleavage fracture.

Claims

1. An iron-manganese alloy having high work hardening ability; the method is characterized in that: in the ferro-manganese alloy, the content of Mn is 17.5-18.5wt%, the content of oxygen is less than or equal to 0.03wt%, and the balance is ferrum; the yield strength of the iron-manganese alloy is 220-300MPa, and the ultimate tensile strength is 870-998MPa.

2. A high work-hardenability iron-manganese alloy according to claim 1; the method is characterized in that: the iron-manganese alloy takes Fe-Mn prealloying powder as a raw material; preparing a printing blank by adopting a 3D printing technology, and then carrying out heat treatment at 450-700 ℃ under a protective atmosphere; and obtaining a product, wherein the 3D printing parameters are as follows: the laser power is 200-220W, and the scanning speed is 680-720mm/s;

the structure of the printing blank consists of acicular martensite, cellular subgrain and columnar subgrain;

compared with a printing blank, the finished product has the advantages that cellular subgrades and columnar subgrades are still stable, the size is not changed, but the acicular alpha 'martensite is uniformly distributed in the matrix and the size is smaller than that of the acicular alpha' martensite in the printing blank; the phase volume fraction of epsilon martensite in the finished product is greater than the phase volume fraction of epsilon martensite in the print blank, as compared to the print blank.

3. A high work-hardenability iron-manganese alloy according to claim 1; the method is characterized in that: after heat treatment, the yield strength of the product is 294-296MPa, the ultimate tensile strength is 995-997MPa, and the elongation at break is 16.2-16.3%; compared with a printing blank, the yield strength, the ultimate tensile strength and the elongation at break of the printing blank are all improved, and the difference value of the ultimate tensile strength and the yield strength of a finished product is larger than the corresponding value of the printing blank.

4. A method for producing a high work-hardenability iron-manganese alloy according to any one of claims 1 to 3, characterized by: the printing ink is prepared by matching 3D printing and heat treatment; the method comprises the following specific steps:

taking Fe-Mn prealloying powder as a raw material; preparing a printing blank by adopting a 3D printing technology, and then carrying out heat treatment at 450-700 ℃ under a protective atmosphere; the product is obtained by the method of the invention,

The tensile strength of the product is more than or equal to 884MPa.

5. The method for producing a high work-hardenability iron-manganese alloy according to claim 4; the method is characterized in that: the grain size of the Fe-Mn prealloyed powder is 15-53 mu m.

6. The method for producing a high work-hardenability iron-manganese alloy according to claim 4; the method is characterized in that:

the parameters for 3D printing are: the laser power was 210W, the scanning speed was 700mm/s, the scanning pitch was 80 μm, and the layer thickness was 30 μm.

7. The method for producing a high work-hardenability iron-manganese alloy according to claim 4; the method is characterized in that:

the heat treatment temperature is 645-655 ℃, the heat preservation time is 80-100min, and the cooling mode is furnace cooling.

8. The method for producing a high work-hardenability iron-manganese alloy according to claim 4; the method is characterized in that:

the printing blank has yield strength of 205-207MPa, ultimate tensile strength of 883-885MPa, and elongation at break of 15.8-15.85%.

The product after heat treatment has yield strength of 294-296MPa, ultimate tensile strength of 995-997MPa and elongation at break of 16.2-16.3%.

9. Use of a high work-hardening iron manganese alloy according to any one of claims 1 to 3, characterized in that: including use as a bioimplant material.