阅读说明：本技术 兼具高强度和高弹性应变的TiHfFeNiNbx定向凝固高熵合金及其制备 (TiHfFeNiNb with high strength and high elastic strainxDirectional solidification high-entropy alloy and preparation thereof ) 是由 朱正旺 李欢 张海峰 张宏伟 付华萌 李宏 王爱民 张龙 李正坤 李松涛 于 2021-07-22 设计创作，主要内容包括：一种兼具高强度和高弹性应变的TiHfFeNiNb-(x)定向凝固高熵合金及其制备方法,属于金属材料技术领域。该定向凝固高熵合金的组成元素为Ti、Hf、Fe、Ni、Nb,各组分原子百分比为：30：10：10：30：x。定向凝固生长速度范围为0～180mm/h,定向凝固旋转速度范围为0～60rpm。该类合金在定向凝固后,合金横截面由烟花状的团簇组成,而纵截面却呈现出了不同的形貌特征,即呈现出了不同程度的方向性。合金的晶体结构为BCC+B2。合金的拉伸过程中,展现了高的弹性应变。(TiHfFeNiNb with high strength and high elastic strain x A directional solidification high-entropy alloy and a preparation method thereof belong to the technical field of metal materials. The directional solidification high-entropy alloy comprises the following components in percentage by atom: 30: 10: 10: 30: x. The range of the growth speed of the directional solidification is 0-180 mm/h, and the range of the rotation speed of the directional solidification is 0-60 rpm. After the alloy is directionally solidified, the cross section of the alloy consists of firework-shaped clusters, while the longitudinal section of the alloy shows different morphological characteristics, namely shows no appearanceWith the same degree of directionality. The crystal structure of the alloy is BCC + B2. During the elongation of the alloy, a high elastic strain is exhibited.)

1. TiHfFeNiNb with high strength and high elastic strain_xThe directional solidification high-entropy alloy is characterized in that: the atomic percentage expression of the directional solidification high-entropy alloy is Ti₃₀Hf₁₀Fe₁₀Ni₃₀Nb_xAnd the value range of the Nb content x in the components of the directionally solidified high-entropy alloy is 15-30.

2. TiHfFeNiNb with high strength and high elastic strain according to claim 1_xThe directional solidification high-entropy alloy is characterized in that: the purities of the components of titanium, niobium, hafnium, iron and nickel are more than or equal to 99.9 percent, and the pure metal raw materials are all blocky or granular.

3. The preparation method of the TiNbHfFeNi eutectic high-entropy alloy with high strength and high elastic strain according to claim 1, is characterized by comprising the following steps:

step 1), converting the atomic percentage into the mass percentage according to the high-entropy alloy components, and weighing the ingredients;

step 2), removing oxide skins on the surfaces of the weighed raw materials one by one, and ultrasonically cleaning the raw materials by using industrial ethanol;

step 3), placing the processed raw materials in a copper crucible of a vacuum non-consumable electric arc furnace according to the sequence of melting points from low to high; and titanium sponge is put into the rest copper crucible;

step 4) pumping the vacuum chamber in the smelting furnace to the vacuum degree of 1 multiplied by 10^-3～5×10^-3After Pa, argon gas with pressure of-0.05 to-0.1 MPa is filled into the furnace, and the button-shaped ingot is obtained after repeated and uniform smelting;

step 5), putting the button-shaped cast ingot into an Edmund Buehler arc furnace, and turning over the liquid into a copper mold after smelting to obtain the button-shaped cast ingotThe mother bar of (4);

and 6) melting the bottom of the mother rod by using an optical floating zone furnace, solidifying the bottom of the mother rod on a base with the same components, gradually moving a light focusing point upwards, and controlling the growth speed of the directional solidification by controlling the upward moving speed of the light focusing point, wherein the growth speed range is 1-180 mm/h, and the rotation speed range is 0-60 rpm in the directional solidification process.

4. The preparation method of the TiNbHfFeNi eutectic high-entropy alloy with high strength and high elastic strain according to claim 3, characterized by comprising the following steps: in the step 1), raw materials Ti is sponge titanium, Nb is niobium particles, Hf is crystallized hafnium, Fe is iron blocks, and Ni is nickel particles.

5. The preparation method of the TiNbHfFeNi eutectic high-entropy alloy with high strength and high elastic strain according to claim 3, characterized by comprising the following steps: in the step 4), magnetic stirring is started in the process of repeatedly and uniformly smelting for multiple times, wherein the smelting times are 4 times.

6. TiHfFeNiNb with high strength and high elastic strain prepared by the method of claim 3_xThe directional solidification high-entropy alloy is characterized in that: the TiHfFeNiNb_xThe microstructure of the directionally solidified high-entropy alloy is an irregular eutectic structure consisting of a Nb-rich BCC phase and a Nb-poor B2 phase.

7. TiHfFeNiNb with high strength and high elastic strain according to claim 6_xThe directional solidification high-entropy alloy is characterized in that: the compressive yield strength range of the directionally solidified high-entropy alloy is 1600-2174 MPa, and the elastic strain range is 2.52-3.73%.

Technical Field

The invention belongs to the field of designed metal materials and preparation thereof, and particularly relates to TiHfFeNiNb with high strength and high elastic strain_xA directional solidification high-entropy alloy and a preparation method thereof.

Background

The key point of the directional solidification technology is that various properties of the material are related to the distribution and the shape of a microstructure, and the shape of the microstructure depends on the temperature gradient of a solid-liquid interface in a solidification stage and the distribution among elements. Therefore, how to regulate and control the mass transfer and the heat transfer of the solid-liquid interface in the solidification stage is an important research direction for the development of the directional solidification theory. The heat conduction direction in the solidification stage is regulated and controlled through the directional solidification technology, so that the appearance and the growth mode of the microstructure are regulated and controlled, the microstructure is arranged towards a determined direction, and excellent physical properties and mechanical properties are obtained. High entropy alloys are a revolutionary new concept proposed in recent years. But the research on applying the directional solidification preparation technology to the example of the high-entropy alloy is limited.

Disclosure of Invention

The invention develops TiHfFeNiNb with high strength and high elastic strain_xThe cross section of the directionally solidified high-entropy alloy is composed of firework-like clusters, while the longitudinal section of the directionally solidified high-entropy alloy showsDifferent morphological features, i.e. presenting different degrees of directionality, the alloy has a two-phase (BCC + B2) structure.

The technical scheme of the invention is as follows:

TiHfFeNiNb with high strength and high elastic strain_xThe directional solidification high-entropy alloy is characterized in that: the atomic percentage expression of the directional solidification high-entropy alloy is Ti₃₀Hf₁₀Fe₁₀Ni₃₀Nb_xAnd the value range of the Nb content x in the components of the directionally solidified high-entropy alloy is 15-30.

The purity of the alloy constituent elements titanium, niobium, hafnium, iron and nickel is more than or equal to 99.9 percent, and the pure metal raw materials are all blocky or granular.

The invention also aims to provide a method for directionally solidifying the TiNbHfFeNi high-entropy alloy, which is characterized by comprising the following steps:

step 1), converting the atomic percentage into the mass percentage according to the high-entropy alloy components, and weighing the ingredients;

step 2), removing oxide skins on the surfaces of the weighed raw materials one by one, and ultrasonically cleaning the raw materials by using industrial ethanol;

step 3), placing the processed raw materials in a copper crucible of a vacuum non-consumable electric arc furnace according to the sequence of melting points from low to high; and titanium sponge is put into the rest copper crucible;

step 4) pumping the vacuum chamber in the smelting furnace to the vacuum degree of 1 multiplied by 10^-3Pa～5×10^-3After Pa, argon gas with pressure of-0.05 to-0.1 MPa is filled into the furnace, and the button-shaped ingot is obtained after repeated and uniform smelting;

step 5), putting the button-shaped cast ingot into an Edmund Buehler arc furnace, and turning over the liquid into a copper mold after smelting to obtain the button-shaped cast ingotThe mother bar of (4);

and 6) melting the bottom of the mother rod by using an optical floating zone furnace, solidifying the bottom of the mother rod on a base with the same components, gradually moving a light focusing point upwards, controlling the growth speed of directional solidification by controlling the upward moving speed of the light focusing point, wherein the growth speed range is 1-180 mm/h, the rotation speed range is 0-60 rpm in the directional solidification process, the elastic strain and the strength of the high-entropy alloy prepared by the directional solidification technology are greatly improved, and the microstructure is more complex.

As a preferred technical scheme:

in the step 1), raw materials Ti is sponge titanium, Nb is niobium particles, Hf is crystallized hafnium, Fe is iron blocks, and Ni is nickel particles.

In the step 4), magnetic stirring is started in the process of repeatedly and uniformly smelting for multiple times, wherein the smelting times are 4 times.

Compared with the prior art, the invention has the advantages that:

1. TiHfFeNiNb designed by the invention_xThe preparation method of the directional solidification high-entropy alloy is novel, and the directional solidification technology is applied to the high-entropy alloy concept, and the advantages are taken.

2. The invention provides TiHfFeNiNb_xThe microstructure of the directionally solidified high-entropy alloy is not proposed in reports, and is an irregular eutectic structure consisting of a Nb-rich BCC phase and a Nb-poor B2 phase for the first time. The structure will promote the elastic strain of the alloy and the strength of the alloy. The fiber tissue prepared by the directional solidification technology can present directionality, and the mechanical property of the tissue with directionality can be improved.

3. The invention provides TiHfFeNiNb_xThe directionally solidified high-entropy alloy has high tensile strength and high elastic strain in a room temperature tensile test. High yield strength and high elastic strain in room temperature compression tests. Wherein the compressive yield strength range is 1600MPa to 2174MPa, and the elastic strain range is 2.52 percent to 3.73 percent.

Drawings

FIG. 1 is a comparison of X-ray diffractometry (XRD) patterns of directionally solidified high entropy alloys prepared in examples 1-6;

FIG. 2 is a graph comparing the quasi-static tensile engineering stress-strain curves of the directionally solidified high entropy alloys prepared in examples 1-6;

FIG. 3 is a graph comparing the quasi-static compressive engineering stress-strain curves of directionally solidified high entropy alloys prepared in examples 1-6;

FIG. 4 is a comparison of quasi-static high temperature compressive true stress-strain curves for directionally solidified high entropy alloys prepared in example 1;

FIG. 5 is a scanning electron microscope picture of a directionally solidified high entropy alloy prepared in example 1 (images A and B are cross-sectional scanning pictures, and images C and D are longitudinal-sectional scanning pictures);

FIG. 6 is a scanning electron microscope picture of a directionally solidified high entropy alloy prepared in example 2 (a picture A is a cross-sectional scanning picture, and a picture B is a longitudinal-sectional scanning picture);

FIG. 7 is a scanning electron microscope picture of a directionally solidified high entropy alloy prepared in example 3 (a picture A is a cross-sectional scanning picture, and a picture B is a longitudinal-sectional scanning picture);

FIG. 8 is a scanning electron microscope picture of a directionally solidified high entropy alloy prepared in example 4 (a picture A is a cross-sectional scanning picture, and a picture B is a longitudinal-sectional scanning picture);

FIG. 9 is a scanning electron micrograph of a directionally solidified high entropy alloy prepared in example 5 (FIG. A is a cross-sectional scanning photograph and FIG. B is a longitudinal-sectional scanning photograph);

FIG. 10 is a scanning electron microscope picture of a directionally solidified high entropy alloy prepared in example 6 (a picture A is a cross-sectional scanning picture, and a picture B is a longitudinal-sectional scanning picture).

Detailed Description

The technical scheme of the invention is clearly and completely described in the following with reference to the accompanying drawings and specific embodiments.

Example 1

Ti with high strength and high elastic strain₃₀Hf₁₀Fe₁₀Ni₃₀Nb₂₀The directional solidification growth speed of the directionally solidified high-entropy alloy is 60 mm/h. The directional solidification rotation speed is 15 rpm. The method comprises the following specific steps:

(1) preparing raw materials: the metal raw material used is high-purity (more than or equal to 99.9%). Wherein, the raw material Ti is sponge titanium, Nb is niobium particles, Hf is crystallized hafnium, Fe is iron block, and Ni is nickel particles. Weighing and proportioning according to the mass ratio, removing oxide skin on the surface of the raw material, cleaning by ultrasonic oscillation in alcohol, and drying.

(2) Preparing an alloy: the alloy is melted by a vacuum arc furnace. The raw materials of Fe and Ni are separately placed in one copper crucible, and the raw materials of Nb, Hf and Ti are placed in the other copper crucible, so that the intermediate alloy is firstly prepared. Titanium sponge is added into the vacant copper crucible. Vacuum-pumping to 3.5X 10^-3Pa, then filling high-purity argon to-0.08 MPa. And (3) opening magnetic stirring in the smelting process to ensure that the chemical components are uniform. And putting the smelted intermediate alloys together, and smelting the final alloy. The melting is repeated for 4 times.

And (3) finishing alloy smelting, filling air after the furnace body is cooled, opening the furnace door, and taking out an alloy ingot to obtain the as-cast alloy. Putting the button-shaped cast ingot into an Edmund Buehler electric arc furnace, and turning the liquid into a copper mold after smelting to obtain the alloyThe mother bar of (1). Melting the bottom of the mother rod by using an optical floating zone furnace, solidifying the mother rod on a base with the same components, gradually moving a light focusing point upwards, controlling the growth speed of directional solidification by controlling the upward moving speed of the light focusing point, wherein the growth speed is 60mm/h, the rotating speed is 15rpm, and performing organizational structure characterization and mechanical property test.

Referring to FIG. 1, it can be seen that the crystal structure of the alloy is BCC + B2. Referring to fig. 1 and a diagram in fig. 4, it can be seen that the directionally solidified high entropy alloy of the embodiment of the present invention has an irregular eutectic structure composed of a white Nb-rich BCC phase and a black Nb-poor B2 phase in a cross section at room temperature. Referring to fig. 5B, it can be seen that the cross section is covered with irregular eutectic structures. Referring to fig. 5C and D, it can be seen that the longitudinal section is filled with cluster bands in the same direction, and the direction of the cluster bands is parallel to the growth direction of the alloy, which illustrates that the directional solidification technique makes the fiber structure of the alloy grow in a specific direction. The average width of the cluster band is 200 um. Referring to FIG. 2, it can be seen that the alloy has a tensile strength of 1410MPa and an elastic strain of 3.1%. Referring to FIG. 3, it can be seen that the alloy has room temperature compressive yield strength of 2174MPa, compressive strength of 2300MPa, and elastic section as high as 3.73%. Referring to fig. 4, it can be seen that example 1 has excellent high temperature mechanical properties, has a yield strength of 1510MPa in an environment of 500 ℃, an elastic strain of up to 5%, a stress of 2737MPa at a strain of 41%, and exhibits a work hardening phenomenon. The elastic strain of the alloy has a yield strength of 1230MPa in an environment of 600 ℃, and the elastic strain is up to 4.3 percent. At 50% strain, the stress reached a maximum of 2121MPa and the sample did not fracture, while showing a slight work hardening phenomenon. Example 1 exhibited large elastic strain and extremely high strength at various temperatures of 700 c, 800 c, 900 c and 1000 c, and no fracture occurred at strain up to 50%. In conclusion, the alloy prepared in the embodiment 1 has the characteristics of novel and complex microstructure, excellent room-temperature mechanical property and high-temperature mechanical property, high strength, high elastic strain and the like.

Example 2

Ti with high strength and high elastic strain₃₀Hf₁₀Fe₁₀Ni₃₀Nb₂₀The directional solidification growth speed of the directionally solidified high-entropy alloy is 180 mm/h. The directional solidification rotation speed is 15 rpm. The method comprises the following specific steps:

(1) preparing raw materials: the metal raw material used is high-purity (more than or equal to 99.9%). Wherein, the raw material Ti is sponge titanium, Nb is niobium particles, Hf is crystallized hafnium, Fe is iron block, and Ni is nickel particles. Weighing and proportioning according to the mass ratio, removing oxide skin on the surface of the raw material, cleaning by ultrasonic oscillation in alcohol, and drying.

(2) Preparing an alloy: the alloy is melted by a vacuum arc furnace. The raw materials of Fe and Ni are separately placed in one copper crucible, and the raw materials of Nb, Hf and Ti are placed in the other copper crucible, so that the intermediate alloy is firstly prepared. Oxygen-absorbing titanium sponge is added into the vacant copper crucible. Vacuum-pumping to 3.5X 10^-3Pa, then filling high-purity argon to-0.08 MPa. And (3) opening magnetic stirring in the smelting process to ensure that the chemical components are uniform. And putting the smelted intermediate alloys together, and smelting the final alloy. The melting is repeated for 4 times.

And (3) finishing alloy smelting, filling air after the furnace body is cooled, opening the furnace door, and taking out an alloy ingot to obtain the as-cast alloy. Putting the button-shaped cast ingot into an Edmund Buehler electric arc furnace, and smeltingThen turning the liquid into a copper mold to obtainThe mother bar of (1). Melting the bottom of the mother rod by using an optical floating zone furnace, solidifying the mother rod on a base with the same components, gradually moving a light focusing point upwards, controlling the growth speed of directional solidification by controlling the upward moving speed of the light focusing point, wherein the growth speed is 180mm/h, the rotating speed is 15rpm, and performing organizational structure characterization and mechanical property test.

Referring to FIG. 1, it can be seen that the crystal structure of the alloy is BCC + B2. Referring to fig. 1 and a in fig. 6, it can be seen that the directionally solidified high entropy alloy of the embodiment of the present invention has an irregular eutectic structure composed of Nb-rich white BCC phase and Nb-poor black B2 phase in the cross section at room temperature. It can be seen that clusters of irregular eutectic structures are distributed over the cross section. Referring to fig. 6B, it can be seen that the longitudinal section is honeycomb-shaped, illustrating that the longitudinal section of the alloy at the directional solidification growth rate has the lowest directionality. Referring to FIG. 2, it can be seen that the alloy has a tensile strength of 1151MPa and an elastic strain of 2.05%. Referring to FIG. 3, it can be seen that the alloy has a room temperature compressive yield strength of 1858MPa, a compressive strength of 2122MPa, and an elastic section as high as 3.5%. In conclusion, the alloy prepared in the embodiment 2 has the characteristics of novel and complex microstructure, excellent room-temperature mechanical property, high strength, high elastic strain and the like.

Example 3

Ti with high strength and high elastic strain₃₀Hf₁₀Fe₁₀Ni₃₀Nb₂₀The directional solidification growth speed of the directionally solidified high-entropy alloy is 180 mm/h. The directional solidification rotation speed is 0 rpm. The method comprises the following specific steps:

(1) preparing raw materials: the metal raw material used is high-purity (more than or equal to 99.9%). Wherein, the raw material Ti is sponge titanium, Nb is niobium particles, Hf is crystallized hafnium, Fe is iron block, and Ni is nickel particles. Weighing and proportioning according to the mass ratio, removing oxide skin on the surface of the raw material, cleaning by ultrasonic oscillation in alcohol, and drying.

(2) Preparing an alloy: the alloy is melted by a vacuum arc furnace. Raw materials of Fe and Ni are separatedPlacing the raw materials Nb, Hf and Ti in one copper crucible and placing the raw materials Nb, Hf and Ti in another copper crucible, and firstly preparing the intermediate alloy. Oxygen-absorbing titanium sponge is added into the vacant copper crucible. Vacuum-pumping to 3.5X 10^-3Pa, then filling high-purity argon to-0.08 MPa. And (3) opening magnetic stirring in the smelting process to ensure that the chemical components are uniform. And putting the smelted intermediate alloys together, and smelting the final alloy. The melting is repeated for 4 times.

And (3) finishing alloy smelting, filling air after the furnace body is cooled, opening the furnace door, and taking out an alloy ingot to obtain the as-cast alloy. Putting the button-shaped cast ingot into an Edmund Buehler electric arc furnace, and turning the liquid into a copper mold after smelting to obtain the alloyThe mother bar of (1). Melting the bottom of the mother rod by using an optical floating zone furnace, solidifying the mother rod on a base with the same components, gradually moving a light focusing point upwards, controlling the growth speed of directional solidification by controlling the upward moving speed of the light focusing point, wherein the growth speed is 180mm/h, the rotating speed is 0rpm, and performing organizational structure characterization and mechanical property test.

Referring to FIG. 1, it can be seen that the crystal structure of the alloy is BCC + B2. Referring to fig. 1 and a diagram in fig. 7, it can be seen that the directionally solidified high entropy alloy of the present invention comprises irregular eutectic structures composed of Nb-rich white BCC phase and Nb-poor black B2 phase in cross section at room temperature. It can be seen that the cross-section is covered with irregular eutectic structures. Referring to fig. 7B, it can be seen that the longitudinal section is corrugated, illustrating that the longitudinal section of the alloy at the directional solidification growth rate has a low directionality. Referring to FIG. 2, it can be seen that the alloy has a tensile strength of 1188MPa and an elastic strain of 1%. Referring to FIG. 3, it can be seen that the alloy has room temperature compressive yield strength of 1845MPa, compressive strength of 2355MPa, and elastic section as high as 1.5%. In conclusion, the alloy prepared in the embodiment 3 has the characteristics of novel and complex microstructure, excellent room-temperature mechanical property, high strength, high elastic strain and the like.

Example 4

Ti with high strength and high elastic strain₃₀Hf₁₀Fe₁₀Ni₃₀Nb₂₀OrientationSolidifying the high-entropy alloy, wherein the directional solidification growth speed of the high-entropy alloy is 180 mm/h. The directional solidification rotation speed is 60 rpm. The method comprises the following specific steps:

(1) preparing raw materials: the metal raw material used is high-purity (more than or equal to 99.9%). Wherein, the raw material Ti is sponge titanium, Nb is niobium particles, Hf is crystallized hafnium, Fe is iron block, and Ni is nickel particles. Weighing and proportioning according to the mass ratio, removing oxide skin on the surface of the raw material, cleaning by ultrasonic oscillation in alcohol, and drying.

(2) Preparing an alloy: the alloy is melted by a vacuum arc furnace. The raw materials of Fe and Ni are separately placed in one copper crucible, and the raw materials of Nb, Hf and Ti are placed in the other copper crucible, so that the intermediate alloy is firstly prepared. Oxygen-absorbing titanium sponge is added into the vacant copper crucible. Vacuum-pumping to 3.5X 10^-3Pa, then filling high-purity argon to-0.08 MPa. And (3) opening magnetic stirring in the smelting process to ensure that the chemical components are uniform. And putting the smelted intermediate alloys together, and smelting the final alloy. The melting is repeated for 4 times.

And (3) finishing alloy smelting, filling air after the furnace body is cooled, opening the furnace door, and taking out an alloy ingot to obtain the as-cast alloy. Putting the button-shaped cast ingot into an Edmund Buehler electric arc furnace, and turning the liquid into a copper mold after smelting to obtain the alloyThe mother bar of (1). Melting the bottom of the mother rod by using an optical floating zone furnace, solidifying the mother rod on a base with the same components, gradually moving a light focusing point upwards, controlling the growth speed of directional solidification by controlling the upward moving speed of the light focusing point, wherein the growth speed is 180mm/h, the rotating speed is 60rpm, and performing organizational structure characterization and mechanical property test.

Referring to FIG. 1, it can be seen that the crystal structure of the alloy is BCC + B2. Referring to fig. 1 and a in fig. 8, it can be seen that the directionally solidified high entropy alloy of the embodiment of the present invention has an irregular eutectic structure composed of Nb-rich white BCC phase and Nb-poor black B2 phase in the cross section at room temperature. It can be seen that the cross-section is covered with irregular eutectic structures. Dendritic shape in longitudinal section can be seen with reference to diagram B in fig. 8, illustrating that the longitudinal section of the alloy at this directional solidification growth rate has the strongest directionality. Referring to FIG. 2, it can be seen that the alloy has a tensile strength of 1359MPa and an elastic strain of 1.4%. Referring to fig. 3, it can be seen that the alloy has a room temperature compressive yield strength of 1556MPa, a compressive strength of 2391MPa, and an elastic section as high as 2%. In conclusion, the alloy prepared in the embodiment 4 has the characteristics of novel and complex microstructure, excellent room-temperature mechanical property, high strength, high elastic strain and the like.

Example 5

Ti with high strength and high elastic strain₃₀Hf₁₀Fe₁₀Ni₃₀Nb₁₅The directional solidification growth speed of the directionally solidified high-entropy alloy is 180 mm/h. The directional solidification rotation speed is 15 rpm. The method comprises the following specific steps:

(1) preparing raw materials: the metal raw material used is high-purity (more than or equal to 99.9%). Wherein, the raw material Ti is sponge titanium, Nb is niobium particles, Hf is crystallized hafnium, Fe is iron block, and Ni is nickel particles. Weighing and proportioning according to the mass ratio, removing oxide skin on the surface of the raw material, cleaning by ultrasonic oscillation in alcohol, and drying.

(2) Preparing an alloy: the alloy is melted by a vacuum arc furnace. The raw materials of Fe and Ni are separately placed in one copper crucible, and the raw materials of Nb, Hf and Ti are placed in the other copper crucible, so that the intermediate alloy is firstly prepared. Oxygen-absorbing titanium sponge is added into the vacant copper crucible. Vacuum-pumping to 3.5X 10^-3Pa, then filling high-purity argon to-0.08 MPa. And (3) opening magnetic stirring in the smelting process to ensure that the chemical components are uniform. And putting the smelted intermediate alloys together, and smelting the final alloy. The melting is repeated for 4 times.

And (3) finishing alloy smelting, filling air after the furnace body is cooled, opening the furnace door, and taking out an alloy ingot to obtain the as-cast alloy. Putting the button-shaped cast ingot into an Edmund Buehler electric arc furnace, and turning the liquid into a copper mold after smelting to obtain the alloyThe mother bar of (1). Melting the bottom of the mother rod by using an optical floating zone furnace, solidifying the mother rod on a base with the same components, gradually moving a light focusing point upwards, controlling the growth speed of directional solidification by controlling the upward moving speed of the light focusing point,the growth speed is 180mm/h, the rotation speed is 15rpm, and the tissue structure characterization and the mechanical property test are carried out.

Referring to FIG. 1, it can be seen that the crystal structure of the alloy is BCC + B2. Referring to fig. 1 and a in fig. 9, it can be seen that the directionally solidified high entropy alloy of the present invention comprises a hypoeutectic structure composed of Nb-rich white BCC phase and Nb-poor black B2 phase in cross section at room temperature. The short dendrites in the longitudinal section can be seen by referring to the diagram B in FIG. 9, which shows that the longitudinal section of the alloy at the directional solidification growth rate has certain directionality. Referring to FIG. 2, it can be seen that the alloy has a tensile strength of 1123MPa and an elastic strain of 1.5%. Referring to FIG. 3, it can be seen that the alloy has a room temperature compressive yield strength of 1545MPa, a compressive strength of 2415MPa, and an elastic section as high as 1%. In conclusion, the alloy prepared in the embodiment 5 has the characteristics of novel and complex microstructure, excellent room-temperature mechanical property, high strength, high elastic strain and the like.

Example 6

Ti with high strength and high elastic strain₃₀Hf₁₀Fe₁₀Ni₃₀Nb₃₀The directional solidification growth speed of the directionally solidified high-entropy alloy is 180 mm/h. The directional solidification rotation speed is 15 rpm. The method comprises the following specific steps:

(1) preparing raw materials: the metal raw material used is high-purity (more than or equal to 99.9%). Wherein, the raw material Ti is sponge titanium, Nb is niobium particles, Hf is crystallized hafnium, Fe is iron block, and Ni is nickel particles. Weighing and proportioning according to the mass ratio, removing oxide skin on the surface of the raw material, cleaning by ultrasonic oscillation in alcohol, and drying.

(2) Preparing an alloy: the alloy is melted by a vacuum arc furnace. The raw materials of Fe and Ni are separately placed in one copper crucible, and the raw materials of Nb, Hf and Ti are placed in the other copper crucible, so that the intermediate alloy is firstly prepared. Oxygen-absorbing titanium sponge is added into the vacant copper crucible. Vacuum-pumping to 3.5X 10^-3Pa, then filling high-purity argon to-0.08 MPa. And (3) opening magnetic stirring in the smelting process to ensure that the chemical components are uniform. And putting the smelted intermediate alloys together, and smelting the final alloy. The melting is repeated for 4 times.

After the alloy smelting is finished, the furnace body is charged with air after being cooled,and opening the furnace door, and taking out the alloy ingot to obtain the as-cast alloy. Putting the button-shaped cast ingot into an Edmund Buehler electric arc furnace, and turning the liquid into a copper mold after smelting to obtain the alloyThe mother bar of (1). Melting the bottom of the mother rod by using an optical floating zone furnace, solidifying the mother rod on a base with the same components, gradually moving a light focusing point upwards, controlling the growth speed of directional solidification by controlling the upward moving speed of the light focusing point, wherein the growth speed is 180mm/h, the rotating speed is 15rpm, and performing organizational structure characterization and mechanical property test.

Referring to FIG. 1, it can be seen that the crystal structure of the alloy is BCC + B2. Referring to fig. 1 and a in fig. 10, it can be seen that the directionally solidified high entropy alloy of the present invention comprises a hypereutectic structure composed of Nb-rich white BCC phase and Nb-poor black B2 phase in cross section at room temperature. Referring to fig. 10B, the longitudinal section is corrugated, which indicates that the longitudinal section of the alloy at the directional solidification growth rate has a certain directionality. Referring to FIG. 2, it can be seen that the alloy has a tensile strength of 1202MPa and an elastic strain of 0.9%. Referring to FIG. 3, it can be seen that the alloy has a room temperature compressive yield strength of 1574MPa, a compressive strength of 2402MPa and an elastic section as high as 1.7%. In conclusion, the alloy prepared in the embodiment 6 has the characteristics of novel and complex microstructure, excellent room-temperature mechanical property, high strength, high elastic strain and the like.

The invention is not the best known technology.

The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.