阅读说明：本技术 一种高性能细晶FeCoCrNi合金的制备方法 (Preparation method of high-performance fine-grain FeCoCrNi alloy ) 是由 徐连勇 林丹阳 荆洪阳 韩永典 赵雷 吕小青 于 2020-04-22 设计创作，主要内容包括：本发明公开了一种高性能细晶FeCoCrNi合金的制备方法,包括以下步骤：步骤1,采用激光选区熔化方法打印高熵合金,制备得到打印态FeCoCrNi合金；所述激光选区熔化方法打印方法采用FeCoCrNi等摩尔配比的气雾化球形粉末作为原料；步骤2,将所述打印态FeCoCrNi合金沿打印方向进行压缩,得到压缩后FeCoCrNi合金；步骤3,将所述压缩后FeCoCrNi合金退火1.8～2.2h,冷却后得到高性能细晶FeCoCrNi合金。使用本方法仅需一次压缩及退火循环就可以实现晶粒大幅度细化,极大降低生产成本及加工效率。应用本方法可以显著提高材料的强度及塑性,大大提高其应用范围。(The invention discloses a preparation method of a high-performance fine-grain FeCoCrNi alloy, which comprises the following steps: step 1, printing a high-entropy alloy by adopting a selective laser melting method to prepare a printed FeCoCrNi alloy; the printing method of the selective laser melting method adopts gas atomization spherical powder with equal molar ratio of FeCoCrNi as a raw material; step 2, compressing the printed FeCoCrNi alloy along the printing direction to obtain a compressed FeCoCrNi alloy; and 3, annealing the compressed FeCoCrNi alloy for 1.8-2.2 h, and cooling to obtain the high-performance fine-grain FeCoCrNi alloy. The method can realize the great refinement of the crystal grains only by once compression and annealing cycle, thereby greatly reducing the production cost and the processing efficiency. The method can obviously improve the strength and plasticity of the material and greatly improve the application range of the material.)

1. A preparation method of a high-performance fine-grain FeCoCrNi alloy is characterized by comprising the following steps:

step 1, printing a high-entropy alloy by adopting a selective laser melting method to prepare a printed FeCoCrNi alloy;

the printing method of the selective laser melting method adopts gas atomization spherical powder with equal molar ratio of FeCoCrNi as a raw material;

step 2, compressing the printed FeCoCrNi alloy along the printing direction, wherein the compression amount is 45-55%, and obtaining a compressed FeCoCrNi alloy;

and 3, annealing the compressed FeCoCrNi alloy at 700-1100 ℃ for 1.8-2.2 h, and cooling to obtain the high-performance fine-grain FeCoCrNi alloy.

2. The method for preparing the high-performance fine-grain FeCoCrNi alloy according to claim 1, wherein the process of printing the high-entropy alloy sample by the selective laser melting method comprises the following steps: the method comprises the steps of polishing the surface of a substrate by using a stainless steel material until no oxide exists, cleaning oil stain and dirt on the surface by using an organic solvent, carrying out surface sand blasting treatment by using a sand blasting machine, putting high-entropy alloy powder into a printer bin, constructing a block body with a preset size, setting an interlayer rotation angle to be 65-70 degrees to release residual stress, carrying out laser walking off-line programming, vacuumizing the printing bin before printing, wherein the oxygen content is lower than 500ppm, the laser power is 180-220W, the layer thickness is 30-50 mu m, the linear dot distance is 35-40 mu m, the scanning speed is 720-760 mm/s, protecting by using argon atmosphere, printing to obtain a printing FeCoCrNi alloy with a preset size, and cooling along with the bin.

3. The method of claim 2 wherein said substrate is 316L stainless steel with dimensions of 250 x 15mm in step 1.

4. The method for preparing high performance fine crystal FeCoCrNi alloy according to claim 2, wherein in step 1, the substrate surface is polished by an angle grinder until no oxide is formed, the surface is cleaned with acetone and alcohol, and the surface is sand blasted by a sand blasting machine.

5. The method for preparing a high performance fine crystalline FeCoCrNi alloy as claimed in claim 1, wherein step 1, laser additive manufacturing is performed using AM-400 laser 3D printing equipment manufactured by Ranisha.

6. The method for preparing a high performance fine crystalline FeCoCrNi alloy according to claim 1, wherein in step 1, the printed FeCoCrNi alloy gauge is 7 x 7mm or 10 x 80 mm.

7. The method for preparing a high-performance fine-grained FeCoCrNi alloy according to claim 1, wherein in the step 1, the selective laser melting method adopts an AM-400 laser 3D printing device manufactured by Renissha corporation for laser additive manufacturing, a block with the size of 7 x 7mm or 10 x 80mm is built in Renisshaw-QuantAM, the rotation angle between layers is set to 67 degrees to release residual stress, laser walking off-line programming is automatically performed by software, a printing chamber is vacuumized before printing, the oxygen content is lower than 100ppm, the laser power is 200W, the layer thickness is 40 μm, the line dot spacing is 40 μm, the scanning speed is 740mm/s, the protective gas is argon, and the printed FeCoCrNi alloy is cooled for 2 hours along with the chamber after printing.

8. The method for preparing a high performance fine crystalline FeCoCrNi alloy as claimed in claim 1, wherein step 2, the compression is performed in the printing direction using a universal tester.

9. The method of claim 1 wherein said step 2 said reduction is 50%.

Technical Field

The invention belongs to the technical field of alloy materials, and particularly relates to a preparation method of a high-performance fine-grain FeCoCrNi alloy.

Background

High entropy alloys are a new alloy design concept proposed in recent years that achieves suppression of intermetallic compound formation by increasing the system entropy of mixing by using a plurality of main elements in the alloy system. Therefore, the alloy elements tend to exist in the form of solid solution, so that the mechanical properties of the high-entropy alloy are greatly improved. FeCoCrNi alloy is one of high entropy alloys, and its organization is Face Centered Cubic (FCC) and has been studied more and more in recent years due to its higher strength and plasticity. The strength and the plasticity are two most important mechanical properties of the material, a balance exists between the two mechanical properties and is difficult to break, and when one property is improved, the other property is often reduced. Many attempts have been made by the scientific community to improve both properties simultaneously, and the most common method at present is to perform grain refinement by means of annealing after cold rolling. The increase of the total grain boundary area is beneficial to hindering dislocation motion to improve the strength, and simultaneously can increase the cooperative deformation among grains in the deformation process to improve the plasticity, thereby simultaneously improving the strength and the plasticity.

The principle of grain refinement by cold rolling annealing is that deformation energy storage is increased by cold deformation, in the annealing process, the deformation energy storage in the structure drives the annealing recrystallization, and after the recrystallization is finished, coarse grains are changed into fine isometric grains. However, the cold rolling step is complicated and the cost is high. Often more than ten cold rolling cycles and subsequent annealing are required, even early hot rolling and annealing to achieve the simultaneous improvement in strength and plasticity. This is mainly due to the fact that cold rolling uses ingots, which have large grains and very low dislocation density in the crystal. The essence of cold rolling deformation is dislocation movement, and the deformation energy storage is difficult to accumulate due to small obstruction in the dislocation movement, so that obvious grain refining effect is difficult to generate in single annealing.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a preparation method of a high-performance fine-grain FeCoCrNi alloy.

The invention is realized by the following technical scheme:

a preparation method of a high-performance fine-grain FeCoCrNi alloy comprises the following steps:

step 1, printing a high-entropy alloy by adopting a selective laser melting method to prepare a printed FeCoCrNi alloy;

the printing method of the selective laser melting method adopts gas atomization spherical powder with equal molar ratio of FeCoCrNi as a raw material;

step 2, compressing the printed FeCoCrNi alloy along the printing direction, wherein the compression amount is 45-55%, and obtaining a compressed FeCoCrNi alloy;

and 3, annealing the compressed FeCoCrNi alloy at 700-1100 ℃ for 1.8-2.2 h, and cooling to obtain the high-performance fine-grain FeCoCrNi alloy.

In the technical scheme, the process of printing the high-entropy alloy sample by the selective laser melting method comprises the following steps: the method comprises the steps of polishing the surface of a substrate by using a stainless steel material until no oxide exists, cleaning oil stain and dirt on the surface by using an organic solvent, carrying out surface sand blasting treatment by using a sand blasting machine, putting high-entropy alloy powder into a printer bin, constructing a block body with a preset size, setting an interlayer rotation angle to be 65-70 degrees to release residual stress, carrying out laser walking off-line programming, vacuumizing the printing bin before printing, wherein the oxygen content is lower than 500ppm, the laser power is 180-220W, the layer thickness is 30-50 mu m, the linear dot distance is 35-40 mu m, the scanning speed is 720-760 mm/s, protecting by using argon atmosphere, printing to obtain a printing FeCoCrNi alloy with a preset size, and cooling along with the bin.

In the above technical solution, in step 1, 316L stainless steel is adopted as the substrate, and the size is 250 × 250 × 15 mm.

In the above technical scheme, in the step 1, the surface of the substrate is polished by an angle grinder until no oxide exists, oil stains and dirt on the surface are respectively cleaned by acetone and alcohol, and the surface is subjected to sand blasting by a sand blasting machine.

In the above technical solution, in step 1, laser additive manufacturing is performed by using AM-400 laser 3D printing equipment manufactured by renishao corporation.

In the above technical solution, in step 1, the specification of the printed FeCoCrNi alloy is 7 × 7 × 7mm or 10 × 10 × 80 mm.

In the above technical solution, in step 1, the laser selective melting method adopts an AM-400 laser 3D printing device manufactured by Renishaw corporation to perform laser additive manufacturing, and constructs a block with a size of 7 × 7 × 7mm or 10 × 10 × 80mm in Renishaw-QuantAM, an interlayer rotation angle is set to 67 ° to release residual stress, a laser walking off-line programming is automatically performed by software, before printing, the printing cabin is vacuumized, the oxygen content is less than 100ppm, the laser power is 200W, the layer thickness is 40 μm, the line dot spacing is 40 μm, the scanning speed is 740mm/s, the shielding gas is argon, and the printed FeCoCrNi alloy is obtained after printing and cooled for 2 hours along with the cabin.

In the above technical scheme, step 2, adopt universal tester to compress along the direction of printing.

In the above technical solution, in the step 2, the compression amount is 50%.

The invention has the advantages and beneficial effects that:

the principle of annealing after cold rolling to realize grain refinement is as follows: the deformation energy storage of the metal is improved through cold deformation, the deformation energy storage can drive grains to generate recrystallization behavior in the subsequent annealing, and the grain size after recrystallization is obviously smaller than the initial grain size, so that the grain refinement is realized. The prior art cold rolling process uses as-cast metal as the initial state of rolling. The structure is usually coarse isometric crystals, subject to the slow solidification forming process characteristic of the as-cast metal. The improvement of deformation energy storage during cold deformation is mainly provided by the barrier effect of the grain boundaries on dislocation movement, but the coarse isometric crystals have smaller total grain boundary area. Therefore, the traditional cold rolling annealing process needs to increase the pressing amount for achieving the grain refining effect after annealing due to lower deformation energy storage in the rolling process, and the pressing amount is usually more than 80%. Moreover, such a large amount of pressing cannot be performed at one time, and multiple times of pressing are usually required to avoid cracks. Even such Cold rolled grains are usually relatively large and the size of the grains after Cold rolling is reduced, and it is a common practice to perform hot rolling and annealing before Cold rolling to complete grain pre-refinement and ensure the quality after Cold rolling (see Huang, X., et al, Cold-rolling & annealing process for nuclear grain zero-penetration Cr aluminum alloy and production. journal of Materials Processing Tech,2020.277: p. 116434.). These problems add significantly to the complexity and cost of the cold rolling process and process innovation is essential.

In addition, another problem with the existing use of as-cast alloys as starting materials is compositional non-uniformity. During solidification of the ingot, solute redistribution occurs slowly due to solidification. And the high-entropy alloy is easy to generate solute segregation due to the characteristic of more principal elements. Therefore, the ingot generally has macro-segregation and micro-segregation. The common solution is to perform long-time homogenization annealing before hot rolling and cold rolling, so as to solve the problem of uneven components, and the process difficulty and cost are greatly increased by the step.

The invention improves the accumulation efficiency of deformation energy storage in the cold rolling process by changing the initial state of the cold rolling material, thereby improving the grain refinement degree after single cold rolling annealing cycle, improving the production efficiency and reducing the cost. The invention selects FeCoCrNi high-entropy alloy printed by a Selective Laser Melting (SLM) technology as the initial state of the cold-rolled material. The selective laser melting process is one of fast solidification technology and is produced through spreading powder layer by layer and laser scanning. The manufactured metal structure has the characteristics of small crystal grains and texture existing in the grain growth orientation. The FeCoCrNi alloy in the initial state is used as a cold rolling raw material, and the FeCoCrNi high-entropy alloy with high strength and plasticity can be obtained through one-time compression and cold rolling annealing cycle, wherein the compression amount is only 48-52%, and hot rolling and multi-pass cold rolling are not needed. In addition, the SLM rapid solidification process also ensures the uniformity of the printed product, and has no composition segregation. Therefore, no homogenization annealing is required before cold rolling.

The metal block structure manufactured by the SLM process has obvious grain growth texture and dislocation network structure, and the dislocation network direction is consistent with the texture direction. Therefore, the compression deformation of the printed piece parallel to the texture direction can greatly improve the accumulation of deformation energy storage, thereby increasing the recrystallization behavior of crystal grains in the annealing process and realizing the refinement of the crystal grains. By using the method, the crystalline grains can be greatly refined by only one compression and annealing cycle of the FeCoCrNi alloy SLM printing sample, so that the production cost and the processing efficiency are greatly reduced. The method can obviously improve the strength and plasticity of the material and greatly improve the application range of the material. The method is beneficial to promoting the actual service process of FeCoCrNi alloy.

Drawings

FIG. 1 is a schematic representation of the dimensions of the tensile strength test specimens of example 1 after compression annealing;

FIG. 2 is SEM morphology of a printed FeCoCrNi high-entropy alloy in example 1;

FIG. 3 is SEM morphology of a FeCoCrNi high-entropy alloy after compression in example 1;

FIG. 4 is SEM morphology of a final FeCoCrNi high-entropy alloy obtained after annealing in example 1;

FIG. 5 is an EBSD representation of the final FeCoCrNi high entropy alloy obtained after annealing in example 1;

FIG. 6 is TEM microstructure of FeCoCrNi high-entropy alloy in example 1 in a printed state;

FIG. 7 is TEM microstructure of FeCoCrNi high-entropy alloy after compression in example 1;

FIG. 8 is an EBSD pole figure of FeCoCrNi high entropy alloy in the printed state in example 1;

FIG. 9 is a schematic representation of the texture space structure of a printed FeCoCrNi high entropy alloy;

FIG. 10 is TEM microstructure of FeCoCrNi high-entropy alloy obtained after annealing in example 1 and having refined grains;

FIG. 11 is a stress-strain plot of the as-printed FeCoCrNi high-entropy alloy and the final annealed FeCoCrNi high-entropy alloy of example 1;

FIG. 12 is SEM structural morphology of a final FeCoCrNi high-entropy alloy obtained after annealing in comparative example 1;

FIG. 13 shows TEM texture (recrystallized portion) of the final FeCoCrNi high-entropy alloy obtained in comparative example 1 after annealing;

FIG. 14 shows TEM texture (unrecrystallized part) of the final FeCoCrNi high-entropy alloy obtained in comparative example 1 after annealing;

FIG. 15 is a stress-strain plot of the printed FeCoCrNi high-entropy alloy and the final FeCoCrNi high-entropy alloy obtained after annealing in comparative example 1;

FIG. 16 is SEM structural morphology of a FeCoCrNi high-entropy alloy obtained after annealing in comparative example 2 and after grain refinement;

FIG. 17 is a stress-strain plot of the printed FeCoCrNi high-entropy alloy and the final FeCoCrNi high-entropy alloy obtained after annealing in comparative example 2.

For a person skilled in the art, other relevant figures can be obtained from the above figures without inventive effort.

Detailed Description

In order to make the technical solution of the present invention better understood, the technical solution of the present invention is further described below with reference to specific examples.

Example 1

The laser selective melting method is used for printing the high-entropy alloy to prepare the printing-state FeCoCrNi alloy

The printing powder adopts gas atomization spherical powder with FeCoCrNi equal molar ratio. 316L stainless steel is selected as the substrate, and the size is 250mm multiplied by 15 mm. And (3) cleaning the greasy dirt and the smudged dirt on the surface respectively by using acetone and alcohol. The surface blasting treatment was performed using a sandblaster.

The method comprises the steps of printing by using AM-400 laser 3D printing equipment produced by Renisshaw-Quantam, constructing a block with the size of 10mm multiplied by 80mm in Renisshaw-Quantam self-contained software of the Renisshaw-Quantam equipment, wherein the power is 200W, the layer thickness is 40 mu m, the interlayer rotation angle is 67 degrees, the line spacing is 40 mu m, the scanning speed is 740mm/s, vacuumizing is carried out in a printing bin before printing, the oxygen content is lower than 100ppm, argon protection is adopted, and a printed test piece is cooled for 2 hours along with the bin to obtain a printed test piece.

The sample in the printed state was compressed in the printing direction (see fig. 1) using a universal tester at a compression amount of 50% to obtain a compressed sample.

Annealing the compressed sample at 900 ℃ for 2h, and then cooling along with the furnace to obtain the fine-grain FeCoCrNi high-entropy alloy with greatly improved strength and plasticity.

For tensile and impact property detection, a fine-grained FeCoCrNi high-entropy alloy sample is processed according to the size shown in FIG. 1. The tensile test was carried out at room temperature using a universal tester at a tensile rate of 2.5X 10^-4And s. The microstructures were collectively characterized using electron back-scattered diffraction (EBSD), Transmission Electron Microscopy (TEM), and Scanning Electron Microscopy (SEM).

The elongation after fracture is usually used as an important index for measuring the plasticity of the material. The adopted method is that the gauge length is measured before the tensile experiment, the fracture is realigned after the sample is broken, and the length of the gauge length is measured again, and the ratio of the extension part of the gauge length to the original gauge length is the elongation rate after the fracture.

The texture of the printed FeCoCrNi is shown in FIG. 2, a large number of substructures exist in the crystal grains, and the directions of the substructures are consistent with the directions of the crystal grains (the directions of the substructures are marked by solid lines). After compression, both grains and substructures are distorted (see fig. 3, the initial orientation of the substructures is indicated by the solid lines and the orientation after compression is indicated by the dashed lines). It can be seen that the sub-structures deform along with the deformation of the crystal grains, and the uncoordinated deformation of the sub-structures accumulates a large amount of deformation energy storage at the junctions of the sub-structures, so as to provide power for the recrystallization behavior in the subsequent annealing. After FeCoCrNi alloy is manufactured and processed by using the printing and compressing modes, the sample is annealed for 2 hours at 900 ℃ and then cooled along with the furnace. It was found that the texture (fig. 4) of the finally obtained annealed sample was significantly different from the printed state, the grain size was significantly reduced, the intragranular substructure disappeared, and the grain shape changed from columnar to isometric.

And (3) further characterizing the finally obtained annealed sample by EBSD (Electron Back-scattered diffraction), finding that a large number of annealing twin crystals appear in the crystal, and further dividing the fine crystal grains into smaller crystal grains.

Characterization by transmission electron microscopy revealed that the substructure in the printed FeCoCrNi tissue was actually a dislocation network (see fig. 6). After compression, the dislocation network was deformed but was not lost at all times, and the crystal structure was maintained at the FCC structure (see fig. 7). Thus, the presence of a net of dislocations during the deformation process will significantly affect the deformation process.

FIG. 8 shows an EBSD pole figure of the as-printed texture with a pronounced texture in the {110} crystallographic plane in the Y0 direction, with an intensity of 5.25.

FIG. 9 is a schematic diagram of the printed organization and spatial structure. Due to the presence of the texture, the use of the texture direction as the growth direction (Y0) of the crystal grains is representative. As FeCoCrNi is organized into an FCC structure, the slip plane is a {111} crystal plane. Therefore, it can be concluded from the relationship between the {111} crystal plane and the crystal space structure in FIG. 9 that the slip plane intersects the dislocation network during deformation. Relevant studies have shown that dislocation networks in SLM prints can largely impede dislocation glide. Therefore, the crossing of the slip plane and the dislocation network can increase the blocking effect of the dislocation network on dislocation, thereby increasing the accumulation of system deformation energy storage and finally leading to the improvement of the grain annealing refinement degree.

By TEM (transverse electric field) characterization of the final FeCoCrNi high-entropy alloy after annealing (see figure 10), it can be obviously seen that the grains are refined, and a large amount of dislocation plug products exist at fine grain boundaries. Thus, FeCoCrNi prints processed by this method would have greatly improved tensile strength. And the increase of the surface area of the grain boundary can increase the cooperative deformation among grains, thereby improving the plasticity.

FIG. 11 shows the tensile curve of the sample after one pass of compression annealing compared to the tensile curve of the as-printed sample. The strength and plasticity of the material are greatly improved. The tensile strength of the printed sample is 705.9 +/-12.8 MPa, and the elongation after fracture is 35.3 +/-2.8%. After compression and 900 ℃ annealing treatment, the tensile strength is 806.7 +/-14.8 MPa, and the elongation after fracture is 55.8 +/-2.1%.

Example 2

The laser selective melting method is used for printing the high-entropy alloy to prepare the printing-state FeCoCrNi alloy

The printing powder adopts gas atomization spherical powder with FeCoCrNi equal molar ratio. 316L stainless steel is selected as the substrate, and the size is 250mm multiplied by 15 mm. And (3) cleaning the greasy dirt and the smudged dirt on the surface respectively by using acetone and alcohol. The surface blasting treatment was performed using a sandblaster.

The method comprises the steps of printing by using AM-400 laser 3D printing equipment produced by Renisshaw-Quantam, constructing a block with the size of 10mm multiplied by 80mm in Renisshaw-Quantam self-contained software of the Renisshaw-Quantam equipment, wherein the power is 200W, the layer thickness is 40 mu m, the interlayer rotation angle is 67 degrees, the line spacing is 40 mu m, the scanning speed is 740mm/s, vacuumizing is carried out in a printing bin before printing, the oxygen content is lower than 100ppm, argon protection is adopted, and a printed test piece is cooled for 2 hours along with the bin to obtain a printed test piece.

The sample in the printed state was compressed in the printing direction (see fig. 1) using a universal tester at a compression amount of 50% to obtain a compressed sample.

And annealing the compressed sample at 700 ℃ for 2.2h, and then cooling the sample along with the furnace to obtain the FeCoCrNi high-entropy alloy.

The structure is divided into two parts of recrystallization and non-recrystallization (see fig. 12), the grains of the recrystallized part are fine, and the grains of the non-recrystallized part are coarse. The recrystallization part has a large amount of annealing twin crystals, and the grain refinement is obvious. And the non-recrystallized part has a plurality of deformed twins and obvious dislocation tangle. The characterization results indicated that recrystallization was incomplete after low temperature annealing at 700 degrees. In the recrystallized portion, dislocation plug product caused by grain refinement is significant. As shown in fig. 13, the dislocation density is high, and fine crystal grain boundaries and twin crystal grain boundaries generate a blocking effect on the dislocations to thereby improve the strength. The fine crystalline regions also contribute to the improvement in plasticity, since they are more susceptible to synergistic deformation during deformation. FIG. 14 shows a non-recrystallized portion in which the grains are not refined, but a plurality of deformed twins which are mutually staggered form a twin net-like structure, and it can be seen that the dislocation density is high in the meshes of the twin net. Therefore, the twin net can also play a role in pinning dislocations, and also contribute to the improvement of strength.

The mechanical property test result (figure 15) shows that the tensile strength and the plasticity of the sample are both higher than those of the printed sample, and the initial purpose of simultaneously improving the strength and the plasticity is met. The tensile strength of the printed sample is 705.9 +/-12.8 MPa, and the elongation after fracture is 35.3 +/-2.8%. After compression and annealing treatment at 700 ℃, the tensile strength is 800.6 +/-18.4 MPa, and the elongation after fracture is 39.5 +/-2.4%.

Example 3

The laser selective melting method is used for printing the high-entropy alloy to prepare the printing-state FeCoCrNi alloy

The printing powder adopts gas atomization spherical powder with FeCoCrNi equal molar ratio. 316L stainless steel is selected as the substrate, and the size is 250mm multiplied by 15 mm. And (3) cleaning the greasy dirt and the smudged dirt on the surface respectively by using acetone and alcohol. The surface blasting treatment was performed using a sandblaster.

The method comprises the steps of printing by using AM-400 laser 3D printing equipment produced by Renisshaw-Quantam, constructing a block with the size of 10mm multiplied by 80mm in Renisshaw-Quantam self-contained software of the Renisshaw-Quantam equipment, wherein the power is 200W, the layer thickness is 40 mu m, the interlayer rotation angle is 67 degrees, the line spacing is 40 mu m, the scanning speed is 740mm/s, vacuumizing is carried out in a printing bin before printing, the oxygen content is lower than 100ppm, argon protection is adopted, and a printed test piece is cooled for 2 hours along with the bin to obtain a printed test piece.

The sample in the printed state was compressed in the printing direction (see fig. 1) using a universal tester at a compression amount of 50% to obtain a compressed sample.

And annealing the compressed sample at 1100 ℃ for 1.8h, and then cooling the sample along with the furnace to obtain the FeCoCrNi high-entropy alloy.

Due to the higher annealing temperature, there is a phenomenon of grain growth (fig. 16), and the grown grains reduce the total surface area of grain boundaries, causing a decrease in the cooperative deformability, resulting in a decrease in plasticity. Reduced grain boundary strengthening also results in reduced strength. But the majority of the grains are still present in the structure in the form of fine crystalline grains. After the subsequent mechanical property test, the tensile strength and plasticity of the sample are higher than those of the printed sample (FIG. 17). It is shown that the improvement effect of fine grains on plasticity and strength is still higher than the deterioration effect of coarse grains in the sample annealed at 1100 degrees celsius. During the stretching process, fine crystals play a dominant role.

The tensile strength of the printed sample is 705.9 +/-12.8 MPa, and the elongation after fracture is 35.3 +/-2.8%. After compression and annealing treatment at 1100 ℃, the tensile strength is 745.6 +/-11.8 MPa, and the elongation after fracture is 51.6 +/-1.8%. The tensile strength and the plasticity of the material are both higher than those of a printing-state sample, and the material meets the original purpose of improving the strength and the plasticity at the same time.

Comparative example 1

As a cold rolling starting material, an as-cast FeCoCrNiAl0.1 alloy is used according to the literature description (see Xu, X.D., et al, Microstructural orientations for a Strong and a few Al0.1CoCrFeNi high-entry alloy with ultra fine grains, materials, 2018.4: p.395-405.) and has a composition similar to that of the examples of the present invention. First, a homogenizing annealing at 1200 degrees celsius was performed for 12 hours, and then hot rolling was performed to a reduction of 50%, followed by an annealing at 800 degrees celsius for 1 hour. And (3) starting a cold rolling process, immersing the cold rolled steel in liquid nitrogen to cool for two minutes after each cold rolling, and carrying out the next cold rolling within 3 seconds of leaving the liquid nitrogen, wherein the cold rolling is repeated by the method until the rolling reduction is 89%. Annealing at 580 ℃ for 1 hour to obtain the fine-grained high-entropy alloy.

In the subsequent mechanical property detection, the tensile strength is about 900MPa, and the elongation after fracture is about 23%.

The comparative example shows that the traditional cold rolling process is complicated, and homogenization annealing is performed for improving the component uniformity of the cold rolled material. Hot rolling and annealing are performed to increase the degree of grain refinement in the initial state. In order to obtain a fine grain structure after annealing, the final reduction is increased in cold rolling to improve the deformation energy storage, and multiple passes of reduction are used to avoid cracking in cold rolling. The series of processes greatly increase the complexity of production and increase the cost. Even after such a complicated process, the mechanical properties of the material cannot be improved to the extent that the strength and plasticity of the material are improved by using the present invention.

The invention has been described in an illustrative manner, and it is to be understood that any simple variations, modifications or other equivalent changes which can be made by one skilled in the art without departing from the spirit of the invention fall within the scope of the invention.