CN112222413B - Cold rolling composite laser additive manufacturing process method of gradient structure high-entropy alloy - Google Patents

Abstract

The invention provides a cold-rolled composite laser additive manufacturing process method of a gradient structure high-entropy alloy, which is carried out according to the following steps: first, according to the chemical composition set by the high-entropy alloy, in a high-purity argon atmosphere, vacuum induction melting is adopted The high-entropy alloy ingot is prepared by the process, and the ingot is subjected to homogenization annealing, hot forging and cold rolling. Finally, the selective laser melting technology is used, and the pre-alloyed high-entropy alloy powder is selected as the raw material. Directly on laser additive manufacturing. Because the high-entropy alloy has a delayed diffusion effect and the grain size of the deposited high-entropy alloy is micron, that is, the grain size of the cold-rolled sheet is relatively small, while the grain size of the additive sheet is relatively coarse, and finally a gradient structure is formed. Due to the strong back stress strengthening effect generated by the geometrically necessary dislocation and the strong work hardening ability of the coarse-grained layer, the gradient structure high-entropy alloy prepared by the invention has excellent strength and plasticity.

Description

A cold-rolled composite laser additive manufacturing process method for gradient structure high-entropy alloys

technical field

The invention belongs to the technical field of metal material additive manufacturing, in particular to a cold-rolled composite laser additive manufacturing process method of a gradient structure high-entropy alloy.

Background technique

Additive manufacturing technology has the characteristics of short process and high material utilization rate. It has been used in aerospace, auto parts manufacturing, biomedicine and other fields, and has shown broad application prospects in the preparation of complex components. However, additive manufacturing technology has the bottleneck problem of insufficient mechanical properties of as-deposited metal. That is to say, compared with the high-entropy alloys after plastic deformation + heat treatment, the mechanical properties of laser-additive-manufactured high-entropy alloys are relatively poor.

To this end, many patent applicants have proposed rolling-based composite additive manufacturing technology, shot peening-based composite additive manufacturing technology, laser-assisted composite additive manufacturing technology, etc., to improve the mechanical properties of as-deposited metals. The patent with the application number of 201810528056.2 proposes a device and method for layer-by-layer rolling of laser three-dimensional forming parts, that is, the deposited metal is cold-rolled or hot-rolled layer by layer, and the rolling force of the roller is used to refine grains and increase dislocations. Thereby improving the mechanical properties of laser three-dimensional forming parts; the patent application number 201911146571.5 proposes a composite manufacturing device and method of arc additive and laser-assisted thermoplastic forming, which uses laser to heat the surface of the deposited layer, and then passes through a roller or impact tool head Plastic deformation is applied to the material to refine the grains, improve the microstructure, and improve the comprehensive mechanical properties of the parts.

However, the deformation amount of plastic deformation such as deposition interlaminar rolling is small, and deposition interlaminar cold rolling reduces the plasticity of the material and aggravates the crack tendency, so the existing composite additive manufacturing technology can transform dendrites into equiaxed The anisotropy of the material is improved, but the improvement of the mechanical properties of the metal material is limited. Therefore, a process method that can significantly improve the mechanical properties of laser additive manufacturing of high-entropy alloys needs to be proposed.

SUMMARY OF THE INVENTION

The invention provides a cold-rolled composite laser additive manufacturing process method of a gradient structure high-entropy alloy based on the principle that the strength of the metal material can be improved by cold rolling and the gradient structure can change the strength and plasticity of the traditional metal material, thereby improving the laser additive manufacturing process. Strength and ductility in the manufacture of high-entropy alloys.

In order to achieve the above purpose, the technical scheme of the present invention is:

A cold-rolled composite laser additive manufacturing process method of a gradient structure high-entropy alloy is carried out according to the following steps:

(1) According to the chemical composition set by the high-entropy alloy, in a high-purity argon atmosphere, a high-entropy alloy ingot is prepared by a vacuum induction melting process;

(2) Perform homogenization annealing heat treatment on the high-entropy alloy ingot, the homogenization annealing holding temperature is 1000-1250°C, and the homogenizing annealing holding time is 8-30h;

(3) Hot forging the high-entropy alloy ingot after the homogenization annealing heat treatment into a slab, and the forging temperature is 1080-1140 °C;

(4) The slab is rolled at room temperature, the pass reduction is 0.3-3mm, and the total reduction rate is ≥82%;

(5) Using selective laser melting technology, pre-alloyed high-entropy alloy powder is used as raw material, and laser additive manufacturing is directly carried out on the rolled slab. The spot diameter is 50-100 μm, and the layer thickness is 40-90 μm. The laser power is 170-325W, the scanning rate is 750-2000mm/s, the overlap ratio is 15-50%, and the protective gas is argon.

Preferably, in step (1), smelting needs to be repeated 4 to 7 times.

Preferably, water cooling is adopted after the homogenization annealing and heat preservation described in step (2).

Preferably, in step (3), the heating temperature of the high-entropy alloy ingot before hot forging is 1200±20°C, and the holding time is 2h.

Preferably, in step (4), the thickness of the high-entropy alloy after cold rolling is 2-5 mm, and the surface mechanical grinding treatment is performed on the cold-rolled high-entropy alloy.

Preferably, the particle size of the high-entropy alloy powder in step (5) is 15-53 μm, and is prepared by gas atomization.

The present invention also provides a gradient structure high-entropy alloy prepared by the above method.

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

(1) The present invention obtains a high-entropy alloy with sub-micron or nano-scale grain size through multi-pass cold rolling deformation. And the cold-rolled high-entropy alloy is used as the substrate for laser additive manufacturing, that is, laser additive manufacturing is directly performed on the cold-rolled high-entropy alloy plate. Due to the delayed diffusion effect of high-entropy alloys and the micron-scale grain size of deposited high-entropy alloys, the grain size of cold-rolled sheets is relatively small, while the grain size of additive sheets is relatively coarse, and finally a gradient structure is formed.

(2) The existing rolling composite additive manufacturing process requires a specific device, that is, the arc deposition layer is rolled and deformed by using a roller that moves simultaneously with the welding torch, while the present invention utilizes the existing cold rolling mill and additive manufacturing equipment. It can be realized and the investment of equipment is reduced.

(3) The gradient structure high-entropy alloy prepared by the present invention has excellent strength and plasticity due to the strong back stress strengthening effect produced by geometrically necessary dislocations and the strong work hardening ability of the coarse-grained layer.

Description of drawings

FIG. 1 is a schematic structural diagram of laser additive manufacturing directly on a cold-rolled sheet in the present invention;

FIG. 2 is a schematic diagram of the grain size distribution of the gradient structure high-entropy alloy prepared by the present invention.

Detailed ways

The following non-limiting examples may enable those of ordinary skill in the art to more fully understand the present invention, but do not limit the present invention in any way.

According to GB/T 228-2010, a room temperature tensile test was performed on the gradient structure high-entropy alloy of the present invention on an INSTRON 3369 universal material testing machine.

According to the cold-rolled composite laser additive manufacturing process method of the gradient structure high-entropy alloy of the present invention, the specific implementation cases are as follows:

Example 1

(1) In a high-purity argon atmosphere, a CoCrFeMnNi high-entropy alloy ingot was prepared by a vacuum induction melting process, and smelted repeatedly for 5 times. Its chemical composition is Co 21.22%, Cr 18.34%, Fe 19.70%, Mn19 .32%, Ni 20.94%, the balance is Si, Al, S, P, etc.

(2) The ingot is subjected to homogenization annealing heat treatment, the homogenization annealing holding temperature is 1200 ° C, the homogenizing annealing holding time is 20h, and the water cooling method is adopted after the homogenizing annealing and heat preservation.

(3) After homogenization annealing heat treatment, the ingot is kept at 1180℃ for 2h, and hot forged into slab at 1090～1120℃.

(4) The slab is rolled at room temperature, the pass reduction is 0.5-2 mm, the total reduction rate is 93.3%, the thickness of the high-entropy alloy after cold rolling is 2 mm, and the surface is subjected to mechanical grinding treatment.

(5) Using selective laser melting technology, select CoCrFeMnNi high-entropy alloy powder with a powder particle size of 15-53 μm (gas atomization), as shown in Figure 1, directly perform laser additive on the cold-rolled slab 1 Manufacturing requires that the spot diameter of the laser beam 2 is 70 μm, the layer thickness is 80 μm, the laser power is 170 W, the scanning rate is 750 mm/s, the overlap rate is 20%, and the protective gas is argon.

The schematic diagram of the grain size distribution of the gradient structure high-entropy alloy in this embodiment is shown in FIG. 2 , that is, the grain size from the cold-rolled sheet to the additive sheet gradually transitions from sub-micron or nano-scale to micro-scale. The tensile strength of the gradient structure CoCrFeMnNi high-entropy alloy is 1085MPa, and the elongation after fracture is 31.2%.

Example 2

(1) In a high-purity argon atmosphere, a CoCrFeMnNi high-entropy alloy ingot was prepared by a vacuum induction melting process, and smelted repeatedly for 4 times. .29%, Ni 20.61%, the balance is Si, Al, S, P, etc.

(2) The ingot is subjected to homogenization annealing heat treatment, the homogenization annealing holding temperature is 1250 ° C, the homogenizing annealing holding time is 15h, and the water cooling method is adopted after the homogenizing annealing and heat preservation.

(3) After homogenization annealing heat treatment, the ingot is kept at 1200℃ for 2h, and hot forged into slab at 1080～1100℃.

(4) The slab is rolled at room temperature, the pass reduction is 0.5-2.5 mm, the total reduction rate is 82.8%, the thickness of the high-entropy alloy after cold rolling is 5 mm, and the surface is subjected to mechanical grinding treatment .

(5) Using selective laser melting technology, select CoCrFeMnNi high-entropy alloy powder (gas atomization forming) with a powder particle size of 15-53 μm, and directly perform laser additive manufacturing on the cold-rolled slab, with a spot diameter of 50 μm and a layer of The thickness is 40μm, the laser power is 230W, the scanning rate is 1100mm/s, the overlap rate is 30%, and the protective gas is argon.

The grain size of the gradient-structured high-entropy alloy in this embodiment gradually transitions from the cold-rolled sheet to the additive sheet from sub-micron or nano-scale to micro-scale. The tensile strength of the gradient structure CoCrFeMnNi high-entropy alloy is 1012MPa, and the elongation after fracture is 36.3%.

Example 3

(1) In a high-purity argon atmosphere, a CoCrFeMnNi high-entropy alloy ingot was prepared by a vacuum induction melting process, and smelted repeatedly for 5 times. .41%, Ni 20.58%, the balance is Si, Al, S, P, etc.

(2) The ingot is subjected to homogenization annealing heat treatment, the homogenization annealing holding temperature is 1200 ℃, the homogenizing annealing holding time is 24h, and the water cooling method is adopted after the homogenizing annealing and heat preservation.

(3) After the homogenization annealing heat treatment, the ingot is kept at 1210 °C for 2 hours, and then hot forged into a slab at 1100-1140 °C.

(4) The slab is rolled at room temperature, the pass reduction is 0.3-2 mm, the total reduction rate is 90.0%, the thickness of the high-entropy alloy after cold rolling is 3 mm, and the surface is subjected to mechanical grinding treatment.

(5) Using selective laser melting technology, select CoCrFeMnNi high-entropy alloy powder with a powder particle size of 15-53 μm (gas atomization), and directly perform laser additive manufacturing on the cold-rolled slab, with a spot diameter of 80 μm and a layer of 80 μm. The thickness is 50μm, the laser power is 325W, the scanning rate is 2000mm/s, the overlap rate is 50%, and the protective gas is argon.

The grain size of the gradient-structured high-entropy alloy in this embodiment gradually transitions from the cold-rolled sheet to the additive sheet from sub-micron or nano-scale to micro-scale. The tensile strength of the gradient structure CoCrFeMnNi high-entropy alloy is 878MPa, and the elongation after fracture is 38.4%.

Example 4

(1) In a high-purity argon atmosphere, a CoCrFeMnNi high-entropy alloy ingot was prepared by a vacuum induction melting process, and smelted repeatedly for 7 times. Its chemical composition is Co 21.11%, Cr 18.49%, Fe 19.63%, Mn19 .68%, Ni 20.71%, the balance is Si, Al, S, P, etc.

(2) Perform homogenization annealing heat treatment on the ingot, the homogenization annealing holding temperature is 1150°C, the homogenizing annealing holding time is 30h, and the water cooling method is adopted after the homogenizing annealing and heat preservation.

(3) After homogenization annealing heat treatment, the ingot is kept at 1220°C for 2 hours, and then hot forged into a slab at 1080-1120°C.

(4) The slab is rolled at room temperature, the pass reduction is 0.5-3 mm, the total reduction rate is 86.7%, the thickness of the high-entropy alloy after cold rolling is 4 mm, and the surface is subjected to mechanical grinding treatment.

(5) Using selective laser melting technology, select CoCrFeMnNi high-entropy alloy powder (gas atomization forming) with a powder particle size of 15-53 μm, and directly perform laser additive manufacturing on the cold-rolled slab, with a spot diameter of 100 μm and a layer of The thickness is 90μm, the laser power is 250W, the scanning rate is 1500mm/s, the overlap rate is 15%, and the protective gas is argon.

The grain size of the gradient-structured high-entropy alloy in this embodiment gradually transitions from the cold-rolled sheet to the additive sheet from sub-micron or nano-scale to micro-scale. The tensile strength of the gradient structure CoCrFeMnNi high-entropy alloy is 994MPa, and the elongation after fracture is 35.9%.

Example 5

(1) In a high-purity argon atmosphere, a CoCuFeMnNi high-entropy alloy ingot was prepared by a vacuum induction melting process, and smelted repeatedly for 5 times. Its chemical composition is Co 19.96%, Cu 21.65%, Fe 19.32%, Mn18 .63%, Ni 19.98%, the balance is Si, Al, S, P, etc.

(2) The ingot is subjected to homogenization annealing heat treatment, the homogenization annealing holding temperature is 1000 ℃, the homogenizing annealing holding time is 8h, and the water cooling method is adopted after the homogenizing annealing and heat preservation.

(3) After homogenization annealing heat treatment, the ingot is kept at 1180℃ for 2h, and hot forged into slab at 1080～1100℃.

(4) The slab is rolled at room temperature, the pass reduction is 0.5-1.5 mm, the total reduction rate is 90.0%, the thickness of the high-entropy alloy after cold rolling is 3 mm, and the surface is subjected to mechanical grinding treatment .

(5) Using selective laser melting technology, select CoCuFeMnNi high-entropy alloy powder with a powder particle size of 15-53 μm (gas atomization), and directly perform laser additive manufacturing on the cold-rolled slab, with a spot diameter of 70 μm and a layer of The thickness is 50μm, the laser power is 200W, the scanning rate is 1500mm/s, the overlap rate is 20%, and the protective gas is argon.

The grain size of the gradient-structured high-entropy alloy in this embodiment gradually transitions from the cold-rolled sheet to the additive sheet from sub-micron or nano-scale to micro-scale. The tensile strength of the gradient structure CoCuFeMnNi high-entropy alloy is 709MPa, and the elongation after fracture is 40.7%.

In addition to the above-described embodiments, the present invention may also have other embodiments. All technical solutions formed by equivalent replacement or equivalent transformation fall within the protection scope of the present invention.

Claims (7)

1. a cold-rolled composite laser additive manufacturing process method of gradient structure high-entropy alloy, is characterized in that, carry out according to the following steps: (1) According to the chemical composition set by the high-entropy alloy, in a high-purity argon atmosphere, a high-entropy alloy ingot is prepared by a vacuum induction melting process; (2) Perform homogenization annealing heat treatment on the high-entropy alloy ingot, the homogenization annealing holding temperature is 1000-1250°C, and the homogenizing annealing holding time is 8-30h; (3) Hot forging the high-entropy alloy ingot after the homogenization annealing heat treatment into a slab, and the forging temperature is 1080-1140 °C; (4) The slab is rolled at room temperature, the pass reduction is 0.3-3mm, and the total reduction rate is ≥82%; (5) Using selective laser melting technology, pre-alloyed high-entropy alloy powder is used as raw material, and laser additive manufacturing is directly carried out on the rolled slab. The spot diameter is 50-100 μm, and the layer thickness is 40-90 μm. The laser power is 170-325W, the scanning rate is 750-2000mm/s, the overlap ratio is 15-50%, and the protective gas is argon. 2 . The cold-rolled composite laser additive manufacturing process for gradient structure high-entropy alloys according to claim 1 , wherein in step (1), 4-7 times of repeated melting is required. 3 . 3 . The cold-rolled composite laser additive manufacturing method for gradient structure high-entropy alloys according to claim 1 , characterized in that, after the homogenization annealing and heat preservation described in step (2), a cooling method of water cooling is adopted. 4 . 4. The cold-rolled composite laser additive manufacturing method for gradient structure high-entropy alloys according to claim 1, characterized in that, in step (3), the heating temperature of the high-entropy alloy ingots before hot forging is 1200±20° C. Time 2h. 5 . The cold-rolled composite laser additive manufacturing process method of gradient structure high-entropy alloy according to claim 1, characterized in that in step (4), the thickness of the high-entropy alloy after cold-rolling is 2-5 mm, and the thickness of the high-entropy alloy after cold rolling is 2-5 mm. The rolled high-entropy alloy is subjected to surface mechanical grinding treatment. 6 . The cold-rolled composite laser additive manufacturing method for gradient structure high-entropy alloys according to claim 1 , wherein in step (5), the powder particle size of the high-entropy alloy powders is 15-53 μm, and aerosols are used. 7 . prepared by chemical forming. 7. The gradient structure high-entropy alloy prepared by the method according to any one of claims 1-6.

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