Dispersion sigma phase reinforced multi-principal element alloy and preparation method thereof

Abstract

The invention relates to a dispersion sigma phase-containing enhanced multi-principal-element alloy and a preparation method thereof, the general formula of chemical components is AlaNibCocCrd according to atomic percent, a is equal to 15, b is greater than or equal to 47 and less than 49, c is greater than 18 and less than or equal to 19, d is greater than 18 and less than or equal to 19, and a + b + c + d is equal to 100. The method has the advantages that the dispersed sigma phase reinforced multi-principal-element alloy is obtained by adopting the proportion of four components of Al, Ni, Co and Cr through alloy burdening and smelting, homogenization treatment, cold rolling deformation, recrystallization heat treatment and aging heat treatment, the Al element is added into a NiCoCr matrix of the alloy, and a double-phase structure of an FCC matrix and a small volume fraction of a BCC phase is obtained.

Description

Technical Field

[0001] The invention belongs to the field of metal material preparation, and in particular relates to a multi-principal element alloy containing dispersed sigma phase reinforcement and a preparation method thereof. Background Art

[0002] For traditional alloys, multi-principal alloys are alloys with multiple principal elements formed by mixing four or more elements in equiatomic ratios or near-equiatomic ratios. Multi-principal alloys can form single-phase solid solutions and dual-phase structures with face-centered cubic (FCC), body-centered cubic (BCC) and hexagonal close-packed (HCP) structures through the regulation and matching of different alloying elements. Compared with single-phase solid solution alloys, casting alloys with dual-phase structures can achieve a combination of high strength and good plasticity at the same time.

[0003] In the prior art, patent publication number: CN114737102A discloses a high-hardness sigma phase high-entropy alloy coating and its preparation method, using high-purity metal powder Co, Cr, Cu, Fe, Mo as raw materials, and using powder plasma arc additive manufacturing technology to obtain high-entropy alloys by layer-by-layer stacking. The high-entropy alloy coating has good quality and no macro defects such as cracks and pores. However, its comprehensive mechanical properties are not ideal. Patent application number: CN202211267692.7 discloses a cast high-entropy alloy with 1GPa tensile strength and good plasticity and its preparation method, which can simultaneously have a combination of high ultimate tensile strength and good plasticity. However, the comprehensive mechanical properties of the cast dual-phase alloy disclosed in the above patent do not have obvious advantages over traditional alloys. The strength of existing cast dual-phase alloys, especially the yield strength, is still relatively low, and the comprehensive mechanical properties need to be further improved. In addition, the low yield strength will seriously limit the engineering application potential of multi-principal alloys. Summary of the invention

[0004] The purpose of the present invention is to provide a multi-principal alloy containing dispersed sigma phase reinforcement and a preparation method thereof, reasonably combining the precipitation strength mechanism, simplifying the preparation process, and improving the yield strength of the cast two-phase alloy, so that the multi-principal alloy has a yield strength of more than 1000MPa and good plasticity greater than 5%.

[0005] To achieve the above object, the present invention is implemented through the following technical solutions:

[0006] A multi-principal alloy containing dispersed sigma phase reinforcement, wherein the chemical composition of the multi-principal alloy is generally represented by Al a Ni b Co c Cr d , where a=15, 47≤b<49, 18<c≤19, 18<d≤19, and a+b+c+d=100.

[0007] The multi-principal alloy has a matrix with an FCC structure and a BCC phase with a volume fraction of 8% to 10%. Meanwhile, a dispersed sigma phase with a size of 0.5 to 1 μm is precipitated in the FCC matrix, and the sigma phase is distributed at the grain boundary.

[0008] The multi-principal alloy has a yield strength of more than 1000 MPa and a plasticity of more than 5%.

[0009] A method for preparing a multi-principal alloy containing a dispersed sigma phase reinforcement comprises the following steps:

[0010] 1) Alloy smelting: Using Al, Ni, Co, and Cr as raw materials, according to Al a Ni b Co c Cr d The ingredients are prepared and mixed, the metal raw materials are heated in a smelting furnace under argon protection until they are melted for alloying, and the smelting is repeated at least 5 times to obtain a master alloy ingot; the master alloy ingot is heated to a completely molten state under argon protection, and suction-casted to obtain a suction-cast alloy ingot;

[0011] 2) Homogenization and cold rolling deformation: Under the protection of argon, the alloy ingots cast by suction are placed in a muffle furnace for heat preservation and homogenization treatment; then the homogenized alloy is rolled at room temperature, and the total rolling deformation is 60% to 80%;

[0012] 3) The alloy plate after cold deformation is subjected to recrystallization treatment and then aging treatment.

[0013] The smelting furnace described in step 1) is a vacuum arc melting furnace or an induction melting furnace.

[0014] In step 1), the alloy is cast by melting in a vacuum arc melting furnace for 5 times and then performing suction casting, or melting in a vacuum induction melting furnace for 3 times and then performing casting.

[0015] The homogenization treatment described in step 2) is to keep the temperature at 1200-1250° C. for more than 48 hours, and then water quench after the alloy is fully homogenized and kept warm.

[0016] The recrystallization treatment in step 3) is a recrystallization annealing at 1000-1050°C for 5-60 minutes followed by water quenching; the aging treatment is an aging at 700-750°C for 24 hours followed by water quenching.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The present invention adopts a ratio of four components Al, Ni, Co, and Cr, and obtains a multi-principal alloy containing dispersed sigma phase reinforcement through alloy batching and smelting, homogenization treatment, cold rolling deformation, recrystallization heat treatment and aging heat treatment. The alloy adds Al element to the NiCoCr matrix to obtain a dual-phase structure of FCC matrix + a small volume fraction of BCC phase.

[0019] 2. The present invention adds Cr element, and the addition of Cr element can improve the oxidation resistance of the alloy and enhance the corrosion resistance of the alloy. At the same time, due to the low solid solubility of Cr element, the alloy has a metastable structure that can precipitate sigma phase. Suitable Al element, high content of Ni element and appropriate proportion of Cr element can ensure that the microstructure is a matrix of FCC structure and a BCC phase with a volume fraction of 8% to 10%, and at the same time generate a large number of dispersed sigma phases with a size of 0.5 to 1μm without generating other impurities to reduce performance.

[0020] 3. The present invention can effectively control the recrystallization volume fraction of the alloy and the size and distribution of the recrystallized grains by combining high-temperature recrystallization heat treatment and medium-temperature aging treatment process, and can also regulate the size and distribution of the sigma phase precipitation. The large amount of precipitation of submicron sigma phase at the grain boundary can effectively increase the yield strength of the alloy to more than 1000MPa, while ensuring that the alloy still has a good plasticity greater than 5%. The present invention can disperse a large amount of submicron sigma phases at the grain boundary to strengthen the matrix, and the grain size can also be regulated by controlling the precipitation and remelting of the sigma phase: increasing the recrystallization treatment time can increase the recrystallization volume fraction and increase the grain size. Using the medium-temperature aging treatment process, a large amount of sigma phase can be precipitated at the grain boundary. The pinned grain size does not grow after the medium-temperature heat treatment. Continuously increasing the recrystallization temperature can cause the sigma phase to melt back into the matrix, and the grain size grows rapidly.

[0021] 4. The alloy prepared by the present invention has excellent and stable performance, simple preparation process, strong safety, moderate price of alloy raw materials, and potential engineering application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the SEM microstructure of the multi-principal alloy 1 prepared in Example 1.

[0023] Figure 2 This is a static tensile engineering stress-strain curve of the multi-principal component alloy 1 prepared in Example 1.

[0024] Figure 3 This is the SEM microstructure of the multi-principal alloy 2 prepared in Example 2.

[0025] Figure 4This is the static tensile engineering stress-strain curve of the multi-principal component alloy 2 prepared in Example 2.

[0026] Figure 5 This is the SEM microstructure of the multi-principal alloy 3 prepared in Example 3.

[0027] Figure 6 This is the static tensile engineering stress-strain curve of the multi-principal element alloy 3 prepared in Example 3. DETAILED DESCRIPTION

[0028] The present invention is described in detail below in conjunction with the accompanying drawings, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0029] Example 1

[0030] A multi-principal alloy containing dispersed sigma phase reinforcement and a preparation method thereof, comprising the following steps:

[0031] 1) The general formula is Al 15 Ni 48.4 Co 18.3 Cr 18.3 (at.%) alloy, wherein the subscript of each element is the atomic percentage of each element, is smelted in a vacuum arc melting furnace, and the smelting is repeated at least 5 times to obtain a mother alloy ingot, so as to ensure that the composition of the smelted alloy is uniform; the smelted mother alloy ingot is placed on a suction casting mold in a vacuum arc melting furnace for suction casting to obtain a multi-principal alloy suction casting ingot, and the preferred suction casting copper mold has a size of 10 mm×10 mm×120 mm.

[0032] 2) The alloy suction cast ingot is vacuum sealed and filled with argon, and then the quartz tube containing the suction cast ingot is directly placed in a muffle furnace, homogenized at 1250°C for 48 hours and then water quenched; the homogenized alloy is then rolled at room temperature with a total rolling deformation of 80±3% to obtain a multi-principal alloy cold-rolled sheet; the cold-rolled sheet is recrystallized annealed at 1000°C for 5 minutes and then water quenched, and then aged at 700°C for 24 hours and then water quenched to obtain a multi-principal alloy reinforced with a dispersed sigma phase.

[0033] 3) A dog-bone tensile specimen with a thickness of 1 mm was cut from the multi-principal alloy sheet by electrospark machining. The gauge length, width and thickness of the tensile specimen were 10 mm, 3 mm and 1 mm respectively. The specimen was tested by a universal testing machine (CMT4305) at a speed of 1×10 -3 The static tensile mechanical properties test was carried out at a fixed strain rate of / s.

[0034] Experimental test analysis:

[0035] The multi-principal alloy containing dispersed sigma phase reinforcement prepared in this embodiment was tested experimentally. Figure 1 From the SEM organization diagram, it can be seen that the prepared multi-principal alloy reinforced with dispersed sigma phase contains a matrix of FCC structure and a small volume fraction of BCC phase, and a large amount of dispersed submicron-scale sigma phase precipitates at the grain boundary of the FCC matrix, and a small amount precipitates within the crystal, with fine grains. According to the tensile test results, the prepared multi-principal alloy reinforced with dispersed sigma phase has a yield strength of 1118MPa, a tensile strength of 1354MPa, and an elongation at break of 7.6%.

[0036] Example 2

[0037] A multi-principal alloy containing dispersed sigma phase reinforcement and a preparation method thereof, comprising the following steps:

[0038] 1) The general formula is Al 15 Ni 48.4 Co 18.3 Cr 18.3 (at.%) alloy, wherein the subscript of each element is the atomic percentage of each element, is melted in a vacuum arc melting furnace to obtain a master alloy ingot; the melted master alloy ingot is placed on a suction casting mold and suction-casted in a vacuum arc melting furnace to obtain a multi-principal alloy suction casting ingot, and the size of the suction casting copper mold is 10mm×10mm×120mm;

[0039] 2) The alloy suction cast ingot is vacuum sealed and filled with argon, and then the quartz tube containing the suction cast ingot is directly placed in a muffle furnace, homogenized at 1250°C for 48 hours and then water quenched; the homogenized alloy is then rolled at room temperature, and the total rolling deformation is 80%, thereby obtaining a multi-principal component alloy cold-rolled sheet; the cold-rolled sheet is recrystallized annealed at 1000°C for 30 minutes and then water quenched, and then aged at 700°C for 24 hours and then water quenched to obtain a multi-principal component alloy containing dispersed sigma phase reinforcement.

[0040] 3) Cutting a dog-bone tensile specimen with a thickness of 1 mm from the multi-principal alloy sheet by an electrospark machining method, wherein the gauge length, width and thickness of the tensile specimen are 10 mm, 3 mm and 1 mm respectively, and using a universal testing machine (CMT4305) at a speed of 1×10 -3 The static tensile mechanical properties test was carried out at a fixed strain rate of / s.

[0041] The multi-principal alloy containing dispersed sigma phase reinforcement in this embodiment is experimentally tested. The prepared multi-principal alloy containing dispersed sigma phase reinforcement contains a matrix of FCC structure and a small volume fraction of BCC phase, and a large amount of dispersed lamellar sigma phase is precipitated at the grain boundary of the FCC matrix, and a small amount is precipitated in the crystal, and the grains are fine. According to the tensile test results, the yield strength of the prepared multi-principal alloy is 1168MPa, the tensile strength is 1277MPa, and the elongation at break is 5.1%.

[0042] Example 3

[0043] A multi-principal alloy containing dispersed sigma phase reinforcement and a preparation method thereof, comprising the following steps:

[0044] 1) The general formula is Al 15 Ni 48 Co 19 Cr 19 (at.%) alloy, wherein the subscript of each element is the atomic percentage of each element, is melted in a vacuum arc melting furnace, and the melting is repeated 5 times to obtain a master alloy ingot; the melted master alloy ingot is placed on a suction casting mold in a vacuum arc melting furnace for suction casting to obtain a multi-principal alloy suction casting ingot, and the size of the suction casting copper mold is 10mm×10mm×120mm;

[0045] 2) The alloy suction cast ingot is vacuum sealed and filled with argon, and then the quartz tube containing the suction cast ingot is directly placed in a muffle furnace, homogenized at 1250°C for 48 hours and then water quenched; the homogenized alloy is then rolled at room temperature, and the total rolling deformation is 80±3%, thereby obtaining a multi-principal component alloy cold-rolled sheet; the cold-rolled sheet is recrystallized annealed at 1000°C for 60 minutes and then water quenched, and then aged at 700°C for 24 hours and then water quenched to obtain a multi-principal component alloy containing dispersed sigma phase reinforcement.

[0046] 3) Cutting a dog-bone tensile specimen with a thickness of 1 mm from the multi-principal alloy sheet by an electrospark machining method, wherein the gauge length, width and thickness of the tensile specimen are 10 mm, 3 mm and 1 mm respectively, and using a universal testing machine (CMT4305) at a speed of 1×10 -3 The static tensile mechanical properties test was carried out at a fixed strain rate of / s.

[0047] The multi-principal alloy reinforced with dispersed sigma phase prepared in this embodiment was experimentally tested. The microstructure of the multi-principal alloy reinforced with dispersed sigma phase prepared includes a matrix of FCC structure and a small volume fraction of BCC phase. At the same time, a large amount of dispersed submicron scale sigma phase is precipitated in the FCC matrix, and the dispersed sigma phase is significantly coarsened. According to the tensile test results, the yield strength of the prepared multi-principal alloy reinforced with dispersed sigma phase is 1133MPa, the tensile strength is 1343MPa, and the elongation at break is 7.9%.

[0048] In summary, the preparation method of the present invention is simple and feasible. The obtained alloy contains a large amount of dispersed submicron-scale sigma phase, and has a yield strength of more than 1000 MPa and good plasticity greater than 5%. It has stable performance, a simple preparation process, and strong safety. It is expected to be produced and applied in the field of engineering applications. The raw materials used are non-toxic and harmless, moderately priced, and have low industrial investment.

[0049] The above embodiments of the present invention are described in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Without departing from the principles of the present invention, any changes, substitutions and modifications made according to the content of the present invention belong to the protection scope of the present invention.

Claims

1. A multi-principal alloy containing dispersed sigma phase reinforcement, characterized in that: The chemical composition of the multi-principal alloy is generally represented by Al in atomic percentage. a Ni b Co c Cr d , where a=15, 47≤b<49, 18<c≤19, 18<d≤19, and a+b+c+d=100.

2. A multi-principal alloy containing dispersed sigma phase enhancement according to claim 1, characterized in that: The multi-principal alloy has a matrix with an FCC structure and a BCC phase with a volume fraction of 8% to 10%. Meanwhile, a dispersed sigma phase with a size of 0.5 to 1 μm is precipitated in the FCC matrix, and the sigma phase is distributed at the grain boundary.

3. The multi-principal alloy containing dispersed sigma phase enhancement according to claim 1, characterized in that: The multi-principal alloy has a yield strength of more than 1000 MPa and a plasticity of more than 5%.

4. A method for preparing a multi-principal alloy containing dispersed sigma phase reinforcement as claimed in any one of claims 1 to 3, characterized in that: The following steps are involved: 1) Alloy smelting: Using Al, Ni, Co, and Cr as raw materials, according to Al a Ni b Co c Cr d The ingredients are prepared and mixed, the metal raw materials are heated in a smelting furnace under argon protection until they are melted for alloying, and the smelting is repeated at least 5 times to obtain a master alloy ingot; Then, under the protection of argon gas, the master alloy ingot is heated to a completely molten state, and suction-casted to obtain a suction-cast alloy ingot; 2) Homogenization and cold rolling deformation: Under the protection of argon, the alloy ingots cast by suction are placed in a muffle furnace for heat preservation and homogenization treatment; then the homogenized alloy is rolled at room temperature, and the total rolling deformation is 60% to 80%; 3) The alloy plate after cold deformation is subjected to recrystallization treatment and then aging treatment.

5. The method for preparing a multi-principal alloy containing dispersed sigma phase reinforcement according to claim 4, characterized in that: The smelting furnace described in step 1) is a vacuum arc melting furnace or an induction melting furnace.

6. The method for preparing a multi-principal alloy containing dispersed sigma phase reinforcement according to claim 3, characterized in that: In step 1), the alloy is cast by melting in a vacuum arc melting furnace for 5 times and then performing suction casting, or melting in a vacuum induction melting furnace for 3 times and then performing casting.

7. The method for preparing a multi-principal alloy containing dispersed sigma phase reinforcement according to claim 4, characterized in that: The homogenization treatment described in step 2) is to keep the temperature at 1200-1250° C. for more than 48 hours, and then water quench after the alloy is fully homogenized and kept warm.

8. The method for preparing a multi-principal alloy containing dispersed sigma phase reinforcement according to claim 4, characterized in that: The recrystallization treatment in step 3) is a recrystallization annealing at 1000-1050°C for 5-60 minutes followed by water quenching; the aging treatment is an aging at 700-750°C for 24 hours followed by water quenching.

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