阅读说明：本技术 一种低密度双相硅化物增强难熔高熵合金及其制备方法 (Low-density dual-phase silicide enhanced refractory high-entropy alloy and preparation method thereof ) 是由 程兴旺 徐子祁 谈燕 马兆龙 于 2021-06-09 设计创作，主要内容包括：本发明涉及一种低密度双相硅化物增强难熔高熵合金及其制备方法,特别涉及一种MoNbTiSi系难熔高熵合金材料及其制备方法,属于高熵合金领域。为了获得具有较低的密度和高强度,该新型合金引用了共晶合金的概念,设计出了两相结构的难熔组织。该合金由Mo、Nb、Ti及Si元素组成,具有硅化物相及BCC相。该新型合金具有高的强度和较好的塑性变形能力,同时其密度在5.5～6.5g/cm～(3)之间。其室温下的屈服强度在1.2GPaMPa以上,断裂应变为15％左右,在1000℃下,其屈服强度为800MPa,断裂应变为20％。由于其特殊的微观组织,其在高温下表现为良好的抗氧化性能。(The invention relates to a low-density dual-phase silicide reinforced refractory high-entropy alloy and a preparation method thereof, in particular to a MoNbTiSi series refractory high-entropy alloy material and a preparation method thereof, belonging to the field of high-entropy alloys. In order to obtain the alloy with lower density and high strength, the novel alloy introduces the concept of eutectic alloy and designs a refractory structure with a two-phase structure. The alloy consists of Mo, Nb, Ti and Si elements, and has a silicide phase and a BCC phase. The novel alloy has high strength and good plastic deformation capability, and the density of the novel alloy is 5.5-6.5 g/cm 3 In the meantime. The yield strength of the alloy is more than 1.2GPaMPa at room temperature, the breaking strain is about 15 percent, and the yield strength is 800MPa at 1000 ℃ and the breaking strain is 20 percent. It exhibits good resistance to oxidation at high temperatures due to its special microstructureAnd (4) performance is improved.)

1. A low-density dual-phase silicide reinforced refractory high-entropy alloy is characterized in that: the composition is MoaNbbTicSid, wherein the atomic percent of a is 20-30%, the atomic percent of b is 20-40%, the atomic percent of c is 20-40%, and the atomic percent of d is 20-25%, wherein d is more than 0.35 a +0.18 b +0.17 c, or d is more than 0.35 a +0.18 b +0.17 c; the alloy composition is a silicide phase and a BCC phase.

2. The low density dual phase silicide-reinforced refractory high entropy alloy of claim 1, wherein: the content of Si is controlled within 25 percent.

3. A method of preparing a low density dual phase silicide reinforced refractory high entropy alloy as claimed in claim 1, wherein: the method comprises the following steps:

step one, sequentially putting the materials into a non-consumable vacuum electric arc melting furnace according to the sequence of the melting points from low to high, namely Si, Ti, Nb and Mo;

pumping the non-consumable vacuum arc melting furnace to a vacuum state, and introducing high-purity argon with the purity of 99.99 wt% as protective gas;

step three, smelting the MoaNbbTicSid alloy until the alloy is completely melted and uniformly mixed, then turning over the master alloy through a manipulator after the master alloy button ingot is cooled, and carrying out the next smelting through the same method for five times; wherein, when smelting for the third time to the fourth time, magnetic stirring is required to be started, so that the high-entropy alloy master alloy ingot is more uniform;

and step four, after the smelting of the MoaNbbTicSid alloy is finished, cooling the copper mold to room temperature, opening the furnace door, and taking out the sample to obtain the MoaNbbTicSid alloy.

Technical Field

The invention relates to a low-density dual-phase silicide reinforced refractory high-entropy alloy and a preparation method thereof, in particular to a MoNbTiSi series refractory high-entropy alloy material and a preparation method thereof, belonging to the field of high-entropy alloys.

Background

The high-entropy alloy is a novel alloy design concept proposed in recent ten years. Compared with the traditional alloy which only has one to two main elements, the high-entropy alloy has a plurality of main elements and forms a single solid solution phase. The characteristics enable the high-entropy alloy to have structural lattice distortion effect, thermodynamic high-entropy effect, kinetic delayed diffusion effect and performance cocktail effect. These effects make the high-entropy alloy have huge application potential in the fields of aerospace, protection, biology and the like. Therefore, in recent years, high-entropy alloys have become a great research hotspot in the field of alloys.

The high-entropy alloy has lattice distortion and delayed diffusion effect, so that the high-entropy alloy has good application prospect in the field of high temperature. At present, the high-melting-point high-entropy alloy is a novel alloy material expected to replace the traditional high-temperature alloy. The WNbMoTa, WNbMoTaV and other refractory high-entropy alloys have high-temperature strength but high density, which is contrary to the current great trend of advocating energy conservation and emission reduction. In addition, the poor oxidation resistance of refractory metals makes these alloys difficult to use under truly high temperature conditions. Some studies have been conducted to reduce the alloy density and improve the oxidation resistance by adding Al, Cr, Si, and the like. However, since these elements usually segregate in the grain boundary to form B2 phase, Laves phase and silicide phase, on the one hand, the mechanical properties are greatly reduced, and on the other hand, these intermetallic compounds have no protective effect on the matrix, so that the oxidation resistance still cannot meet the application requirements. Therefore, how to obtain the oxidation-resistant high-strength refractory high-entropy alloy with low density is urgent.

Disclosure of Invention

The invention aims to solve the problems of high density and poor oxidation resistance of the conventional high-temperature high-entropy alloy, and provides a low-density dual-phase silicide reinforced refractory high-entropy alloy and a preparation method thereof.

The purpose of the invention is realized by the following technical scheme.

A low-density dual-phase silicide reinforced refractory high-entropy alloy comprises MoaNbbTicSid, wherein the atomic percent of a is 20-30%, the atomic percent of b is 20-40%, the atomic percent of c is 20-40%, and the atomic percent of d is 20-25%, wherein d is more than 0.35 a +0.18 b +0.17 c. The alloy composition is a silicide phase and a BCC phase. a + b + c + d equals 100%.

According to Mo-Si, Nb-Si and Ti-Si phase diagrams, the Si content in each binary system is 25.9%, 15.25% and 14.5%, respectively. That is, at the eutectic point, the ratio of Mo to Si is 1: 0.35, Nb-Si ratio of 1: 0.18, Ti-Si ratio of 1: 0.17. the multicomponent eutectic composition can be decomposed into a binary eutectic weighted average according to the multicomponent alloy eutectic formation rule. Therefore, when d is 0.35 a +0.18 b +0.17 c, the alloy composition is a eutectic alloy. In order to improve the oxidation resistance, the Si content is increased so that the silicide becomes a matrix, and the BCC phase is distributed on the silicide matrix to realize the oxidation resistance at high temperature. In order to have better plastic deformation capability, the content of Si is controlled within 25 percent.

The preparation method of the MoaNbbTicSid refractory high-entropy alloy material comprises the following steps:

the method comprises the following steps: selecting five elements of Mo, Nb, Ti and Si, accurately weighing according to atomic percent, and sequentially placing the elements into a copper crucible of a non-consumable vacuum arc melting furnace according to the sequence of melting points from low to high, namely Si, Ti, Nb and Mo.

Step two: and closing the furnace door, pumping the non-consumable vacuum arc melting furnace to a vacuum state, and introducing high-purity argon with the purity of 99.99 wt% as protective gas.

Step three: and smelting the MoaNbbTicSid alloy until the alloy is completely melted and uniformly mixed, then turning over the master alloy by a manipulator after the master alloy button ingot is cooled, and smelting the next time by the same method for five times. And during the third smelting to the fourth smelting, magnetic stirring is required to be started, so that the high-entropy alloy master alloy ingot is more uniform.

Step four: and after the smelting of the MoaNbbTicSid alloy is finished, cooling the copper mold to room temperature, opening the furnace door, and taking out the sample to obtain the MoaNbbTicSid alloy.

Advantageous effects

The invention relates to a low-density dual-phase silicide reinforced refractory high-entropy alloy material which is composed of MoaNbbTicSid and is prepared by a vacuum non-consumable arc melting furnace to obtain a phase composition containing silicide and BCC. Through reasonable component and microstructure design, the MoaNbbTicSid alloy has low density, high-temperature strength and good oxidation resistance.

The SEM and EDS test results show that the alloy consists of a silicide phase and a BCC phase distributed thereon. The MoaNbbTicSid alloy has low density, high room high temperature strength, good plastic deformation capacity and good oxidation resistance. The density is 5.5g/cm³～6.2g/cm³The strength at room temperature can reach more than 1.2GPa, and the compressive fracture strain is about 15 percent. At 1000 ℃, the strength can reach 800MPa, which far exceeds most refractory high-entropy alloys.

Drawings

FIG. 1 is Mo₂₃Nb₂₇Ti₂₆Si₂₄Microstructure of the alloy;

FIG. 2 is Mo₂₃Nb₂₇Ti₂₆Si₂₄Compressive stress strain curves of the alloy at room temperature and 1000 ℃.

Detailed Description

The invention is further described with reference to the following figures and examples.

Example 1

A low-density dual-phase silicide reinforced refractory high-entropy alloy material is characterized by comprising Mo₂₃Nb₂₇Ti₂₆Si₂₄The alloy has a silicide phase and a BCC phase, as shown in FIG. 1.

The Mo₂₃Nb₂₇Ti₂₆Si₂₄The refractory high-entropy alloy material is characterized by comprising the following steps of:

the method comprises the following steps: selecting five elements of Mo, Nb, Ti and Si, accurately weighing according to atomic percent, and sequentially placing the elements into a copper crucible of a non-consumable vacuum arc melting furnace according to the sequence of melting points from low to high, namely Si, Ti, Nb and Mo.

Step two: and closing the furnace door, pumping the non-consumable vacuum arc melting furnace to a vacuum state, and introducing high-purity argon with the purity of 99.99 wt% as protective gas.

Step three: and smelting the MoaNbbTicSid alloy until the alloy is completely melted and uniformly mixed, then turning over the master alloy by a manipulator after the master alloy button ingot is cooled, and smelting the next time by the same method for five times. And during the third smelting to the fourth smelting, magnetic stirring is required to be started, so that the high-entropy alloy master alloy ingot is more uniform.

Step four: wait for Mo₂₃Nb₂₇Ti₂₆Si₂₄After the alloy smelting is finished, cooling the copper mold to room temperature, opening the furnace door, taking out a sample to obtain Mo₂₃Nb₂₇Ti₂₆Si₂₄And (3) alloying.

The alloy was tested for compressive mechanical properties at room temperature and 1000 c as shown in figure 2. Experiments show that: the yield strength of the alloy at room temperature is 1350MPa, the fracture strain is 15 percent, the yield strength of the alloy at 1000 ℃ is 800MPa, and the fracture strain is 20 percent. The density of the alloy was measured to be 6.13g/cm by Archimedes drainage method³. The alloy is oxidized for 6 hours in the heat treatment of 1000 ℃, and the alloy is found to keep better original appearance, which shows that the alloy has better oxidation resistance.

Example 2

A low-density dual-phase silicide reinforced refractory high-entropy alloy material is characterized by comprising Mo₂₄Nb₂₆Ti₂₈Si₂₂The alloy consists of a silicide phase and a BCC phase.

The Mo₂₄Nb₂₆Ti₂₈Si₂₂The refractory high-entropy alloy material is characterized by comprising the following steps of:

the method comprises the following steps: selecting five elements of Mo, Nb, Ti and Si, accurately weighing according to atomic percent, and sequentially placing the elements into a copper crucible of a non-consumable vacuum arc melting furnace according to the sequence of melting points from low to high, namely Si, Ti, Nb and Mo.

Step two: and closing the furnace door, pumping the non-consumable vacuum arc melting furnace to a vacuum state, and introducing high-purity argon with the purity of 99.99 wt% as protective gas.

Step three: for Mo₂₄Nb₂₆Ti₂₈Si₂₂And smelting the alloy until the alloy is completely melted and uniformly mixed, then turning over the master alloy by a manipulator after the master alloy button ingot is cooled, and smelting the next time by the same method for five times. And during the third smelting to the fourth smelting, magnetic stirring is required to be started, so that the high-entropy alloy master alloy ingot is more uniform.

Step four: wait for Mo₂₄Nb₂₆Ti₂₈Si₂₂After the alloy smelting is finished, cooling the copper mold to room temperature, opening the furnace door, taking out a sample to obtain Mo₂₄Nb₂₆Ti₂₈Si₂₂And (3) alloying.

The alloy was tested for compressive mechanical properties at room temperature and 1000 ℃. Experiments show that: the yield strength of the alloy at room temperature is 1250MPa, the breaking strain is 17 percent, the yield strength of the alloy at 1000 ℃ is 780MPa, and the breaking strain is 25 percent. The density of the alloy was measured to be 6.19g/cm by Archimedes drainage method³。

Example 3

A low-density dual-phase silicide reinforced refractory high-entropy alloy material is characterized by comprising Mo₂₀Nb₃₀Ti₃₀Si₂₀The alloy consists of a silicide phase and a BCC phase.

The Mo₂₀Nb₃₀Ti₃₀Si₂₀The refractory high-entropy alloy material is characterized by comprising the following steps of:

the method comprises the following steps: selecting five elements of Mo, Nb, Ti and Si, accurately weighing according to atomic percent, and sequentially placing the elements into a copper crucible of a non-consumable vacuum arc melting furnace according to the sequence of melting points from low to high, namely Si, Ti, Nb and Mo.

Step two: and closing the furnace door, pumping the non-consumable vacuum arc melting furnace to a vacuum state, and introducing high-purity argon with the purity of 99.99 wt% as protective gas.

Step three: for Mo₂₀Nb₃₀Ti₃₀Si₂₀And smelting the alloy until the alloy is completely melted and uniformly mixed, then turning over the master alloy by a manipulator after the master alloy button ingot is cooled, and smelting the next time by the same method for five times. And during the third smelting to the fourth smelting, magnetic stirring is required to be started, so that the high-entropy alloy master alloy ingot is more uniform.

Step four: wait for Mo₂₀Nb₃₀Ti₃₀Si₂₀After the alloy smelting is finished, cooling the copper mold to room temperature, opening the furnace door, taking out a sample to obtain Mo₂₀Nb₃₀Ti₃₀Si₂₀And (3) alloying.

The alloy was tested for compressive mechanical properties at room temperature and 1000 ℃. Experiments show that: the alloy has yield strength of 1210MPa at room temperature and breaking strain of 18 percent, and has yield strength of 750MPa at 1000 ℃ and breaking strain of 30 percent. The density of the alloy was measured to be 6.20g/cm by Archimedes drainage method³。

The foregoing is a description of the preferred embodiments of the present invention. It should be noted that the present invention is not limited to the above embodiments, and any modifications, equivalent replacements, or improvements that can be made to the present invention are included in the protection scope of the present invention when the scope of the claims, the summary of the invention, and the accompanying drawings are satisfied.