A porous high-entropy alloy material and a preparation method thereof

Abstract

The application discloses a kind of porous high-entropy alloy materials, by Ti, Ta, Nb, Zr and Hf element, and the atomic percentage of each element satisfies the following relationship: 2.3≤(1.5[Ti]+2.4[Ta]+2.7[Nb]-2.1[Hf]) / [Zr]≤5.1;Its preparation method is: one, Ti, Ta, Nb, ZrH2 and Hf powder are mixed;Two, with stearic acid powder mix evenly;Three, cold isostatic pressing is pressed;Four, heating defatting and pre-sintering;Five, heating sintering.The application obtains BCC / HCP dual-phase structure by accurate component design, and high hydrogen storage capacity and good activation performance are considered;The application utilizes the in-situ dehydrogenation effect of ZrH2 powder to promote alloying and refine grain, combined with stearic acid and two-step sintering process, the porosity and pore size of material are regulated, fine-grain strengthening is realized, so that material has high porosity and excellent mechanical property, and is suitable for hydrogen storage field.

Description

Technical Field

[0001] This invention belongs to the field of porous metal materials technology, specifically relating to a porous high-entropy alloy material and its preparation method. Background Technology

[0002] Hydrogen energy, as a clean energy carrier with high energy density and zero carbon emissions, is considered one of the key directions for future energy structure transformation. However, efficient, safe, and low-cost hydrogen storage technology remains a bottleneck restricting the large-scale application of hydrogen energy. Compared with traditional high-pressure gaseous hydrogen storage and cryogenic liquid hydrogen storage, metal hydride solid-state hydrogen storage has advantages such as high volumetric hydrogen storage density, mild operating pressure, and good safety, and has attracted widespread attention in recent years. High-entropy alloys, as a class of multi-principal alloys composed of five or more principal elements, have shown unique potential in the field of hydrogen storage due to their high configurational entropy, lattice distortion effect, and adjustable composition design space. Studies have shown that high-entropy alloys with BCC structures typically exhibit higher hydrogen storage capacity, while the Laves phase structure is beneficial for improving hydrogen absorption and desorption kinetics and resistance to disproportionation. However, existing high-entropy alloy hydrogen storage materials are mostly dominated by a single BCC or a single Laves phase, making it difficult to achieve both high hydrogen storage capacity and good activation performance.

[0003] Porous structure design has proven to be an effective strategy for improving the kinetic performance of hydrogen storage alloys. Due to their high specific surface area and nanoscale effect, porous materials can significantly shorten the diffusion path of hydrogen atoms and provide more active sites, thereby achieving rapid hydrogen adsorption / desorption kinetics and good room-temperature activation performance. Currently, researchers have prepared various porous hydrogen storage alloys, such as porous ZrCo alloys and porous TiFe alloys, using powder metallurgy combined with pore-forming agents, all exhibiting excellent hydrogen storage performance. However, research combining porous structure design with BCC / HCP dual-phase high-entropy alloys is still lacking. How to obtain novel porous high-entropy alloy materials that combine high porosity, dual-phase structure, and excellent hydrogen storage performance through compositional control and process optimization still requires further exploration of new technological pathways. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a porous high-entropy alloy material that addresses the shortcomings of the prior art. This method, through precise compositional design to accurately control the phase composition and lattice distortion of the porous high-entropy alloy, obtains a porous high-entropy alloy material with a BCC / HCP dual-phase structure. This material balances high hydrogen storage capacity with good activation performance, resulting in a porous high-entropy alloy material that combines high porosity, dual-phase structure, and excellent hydrogen storage performance. This fills the gap in the prior art regarding the lack of porous high-entropy alloy materials with excellent hydrogen storage performance.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a porous high-entropy alloy material, characterized in that it is composed of Ti, Ta, Nb, Zr and Hf elements, and the atomic percentage of each element satisfies the following relationship: 2.3≤(1.5[Ti]+2.4[Ta]+2.7[Nb]-2.1[Hf]) / [Zr]≤5.1. The microstructure of the porous high-entropy alloy material is a two-phase structure consisting of 70%~98% BCC structure and 2%~30% HCP structure, with a porosity of 0.5%~70%, an average pore size of 0.5µm~65µm, a room temperature compressive strength of 80MPa~2000MPa, and an elastic modulus of 2GPa~30GPa.

[0006] Meanwhile, this invention also discloses a method for preparing the porous high-entropy alloy material as described above, characterized in that the method includes the following steps: Step 1: According to the composition ratio of the target product porous high-entropy alloy material, mix Ti, Ta, Nb, ZrH2 and Hf powders to obtain the first mixed powder; Step 2: Mix the first mixed powder obtained in Step 1 with stearic acid powder until homogeneous to obtain the second mixed powder; Step 3: The second mixed powder obtained in Step 2 is pressed into a green body by cold isostatic pressing; Step 4: Under an argon atmosphere, the green blank from Step 3 is heated, and then degreased and pre-sintered in sequence, and cooled with the furnace to obtain a pre-sintered body; Step 5: Under an argon atmosphere, the pre-sintered body from Step 4 is heated and sintered, then cooled in the furnace to obtain a porous high-entropy alloy material.

[0007] The method described above is characterized in that the particle size range of the Ti, Ta, Nb, ZrH2 and Hf powders mentioned in step one is 0.5µm to 5µm.

[0008] The method described above is characterized in that the particle size range of the stearic acid powder in step two is 5µm to 200µm, and the volume percentage of stearic acid powder in the second mixed powder is 0.1% to 80%.

[0009] The method described above is characterized in that the pressure of the cold isostatic pressing in step three is 100MPa~300MPa, and the holding time is 1min~10min.

[0010] The above method is characterized in that the degreasing temperature in step four is 200℃~500℃ and the holding time is 1h~8h; the pre-sintering temperature is 700℃~1000℃ and the holding time is 1h~5h.

[0011] The method described above is characterized in that the sintering temperature in step five is 1200℃~1500℃, and the holding time is 1h~5h.

[0012] Compared with the prior art, the present invention has the following advantages: 1. Precise control of alloy phase composition by element ratio: Based on the atomic radius and crystal structure characteristics of each element, this invention precisely controls the phase composition and lattice distortion of porous high-entropy alloys by limiting the atomic percentages of five elements, Ti, Ta, Nb, Zr and Hf, to meet specific mathematical relationships. This ensures the formation of a stable BCC / HCP dual-phase structure, avoids the formation of impurity phases, and provides a compositional basis for obtaining excellent hydrogen storage performance.

[0013] 2. Synergistic enhancement of hydrogen storage performance by BCC / HCP dual-phase structure: The porous high-entropy alloy material of the present invention is composed of 70%~98% BCC structure and 2%~30% HCP structure. Among them, the BCC phase serves as the main hydrogen storage phase, providing high hydrogen storage capacity, while the dispersed HCP phase improves the activation performance of the alloy, suppresses the disproportionation reaction during hydrogen absorption and desorption, and enhances the mechanical stability of the material, thus achieving a good balance between hydrogen storage capacity and cycle stability.

[0014] 3. In-situ dehydrogenation of ZrH2 promotes alloying: This invention uses ZrH2 powder instead of metallic Zr powder as raw material. During sintering, zirconium hydride decomposes and releases highly active hydrogen atoms and fresh Zr surface. The in-situ dehydrogenation effect can effectively reduce the oxide film on the powder surface, promote diffusion and alloying between elements, and at the same time, the hydrogen microenvironment is conducive to the formation of pores, reduces the sintering temperature, and refines the grain structure.

[0015] 4. Stearic acid has both pore-forming and bonding functions: This invention uses stearic acid powder as an additive, which acts as a binder to improve the strength of the green body during the cold isostatic pressing stage, and decomposes to form uniform pores during the degreasing stage; at the same time, the instantaneous high-energy environment and residual pores generated during the decomposition of stearic acid can effectively inhibit grain boundary migration and hinder grain growth, thereby refining the grain size of porous high-entropy alloy materials and improving the mechanical properties of the materials.

[0016] 5. Two-step sintering process achieves grain refinement and microstructure stability: This invention employs a two-step process combining pre-sintering and sintering. In the pre-sintering stage (700℃~1000℃), the pre-sintered body undergoes recrystallization, forming a fine equiaxed crystal structure. Subsequently, in the high-temperature sintering stage (1200℃~1500℃), since the pre-sintered body already possesses a stable grain boundary structure, the driving force for grain growth is weakened, and the grain size is maintained as fine. Compared with conventional direct high-temperature sintering after debinding, the two-step sintering process of this invention avoids the grain coarsening problem caused by excessively rapid grain boundary migration, achieving synergistic optimization of fine grain strengthening and porous structure.

[0017] 6. Control of porosity and average pore size by raw material powder: This invention directly uses Ti, Ta, Nb, ZrH2 and Hf element powders instead of pre-alloyed powders. It utilizes the difference in interdiffusion rate of different elements during sintering to induce the Kirkendall effect, generating a large number of pores in situ. By controlling the element ratio, powder particle size, sintering temperature and holding time, and the addition of stearic acid pore-forming agent, the formation and evolution of Kirkendall pores are synergistically controlled, achieving precise control of the porosity (0.5%~70%) and average pore size (0.5µm~65µm) of porous materials.

[0018] The technical solution of the present invention will be further described in detail below through embodiments. Detailed Implementation

[0019] Example 1 The porous high-entropy alloy material in this embodiment is composed of Ti, Ta, Nb, Zr and Hf elements, and the atomic percentage of each element is 20:20:20:20:20. After calculation, (1.5[Ti]+2.4[Ta]+2.7[Nb]-2.1[Hf]) / [Zr]=4.5; The method for preparing porous high-entropy alloy materials in this embodiment includes the following steps: Step 1: According to the composition ratio of the target product porous high-entropy alloy material, mix Ti, Ta, Nb, ZrH2 and Hf powders to obtain the first mixed powder; the particle size range of the Ti, Ta, Nb, ZrH2 and Hf powders is 1µm~2µm. Step 2: Mix the first mixed powder obtained in Step 1 with stearic acid powder evenly to obtain a second mixed powder, wherein the particle size of the stearic acid powder ranges from 5µm to 20µm, and the volume percentage of stearic acid powder in the second mixed powder is 0.1%; Step 3: The second mixed powder obtained in Step 2 is pressed into a green body by cold isostatic pressing. The pressure of cold isostatic pressing is 220 MPa and the holding time is 2 min. Step 4: Under an argon atmosphere, the green blank from Step 3 is heated, and then degreased at 400℃ for 2 hours and pre-sintered at 800℃ for 1 hour, and then cooled with the furnace to obtain a pre-sintered body; Step 5: Under an argon atmosphere, the pre-sintered body from Step 4 is heated to 1450℃ and sintered for 2 hours, then cooled in the furnace to obtain a porous high-entropy alloy material.

[0020] Testing revealed that the microstructure of the porous high-entropy alloy material prepared in this embodiment is a two-phase structure consisting of 95.2% BCC structure and 4.8% HCP structure, with a porosity of 0.7%, an average pore size of 0.9µm, a room temperature compressive strength of 1969MPa, and an elastic modulus of 27.3GPa.

[0021] Example 2 The difference between this embodiment and Embodiment 1 is that the volume percentage of stearic acid powder in the second mixed powder in step two is 40%.

[0022] Testing revealed that the microstructure of the porous high-entropy alloy material prepared in this embodiment is a two-phase structure consisting of 94.4% BCC structure and 5.6% HCP structure, with a porosity of 34.8%, an average pore size of 24.2µm, a room temperature compressive strength of 229MPa, and an elastic modulus of 5.4GPa.

[0023] Example 3 The difference between this embodiment and Embodiment 1 is that the volume percentage of stearic acid powder in the second mixed powder in step two is 60%.

[0024] Testing revealed that the microstructure of the porous high-entropy alloy material prepared in this embodiment is a two-phase structure consisting of 93.2% BCC structure and 6.8% HCP structure, with a porosity of 47.1%, an average pore size of 30.1µm, a room temperature compressive strength of 145MPa, and an elastic modulus of 3.9GPa.

[0025] Example 4 The difference between this embodiment and Embodiment 1 is that the volume percentage of stearic acid powder in the second mixed powder in step two is 80%.

[0026] Testing revealed that the microstructure of the porous high-entropy alloy material prepared in this embodiment is a two-phase structure consisting of 94.2% BCC structure and 5.8% HCP structure, with a porosity of 60.3%, an average pore size of 60.2µm, a room temperature compressive strength of 93MPa, and an elastic modulus of 2.7GPa.

[0027] Example 5 The difference between this embodiment and Embodiment 2 is that the porous high-entropy alloy material is composed of Ti, Ta, Nb, Zr and Hf elements, and the atomic percentage of each element is 24:20:9:42:5. After calculation, (1.5[Ti]+2.4[Ta]+2.7[Nb]-2.1[Hf]) / [Zr]≈2.33.

[0028] Testing revealed that the microstructure of the porous high-entropy alloy material prepared in this embodiment is a two-phase structure consisting of 97.6% BCC structure and 2.4% HCP structure, with a porosity of 28.3%, an average pore size of 17.6µm, a room temperature compressive strength of 305MPa, and an elastic modulus of 7.2GPa.

[0029] Example 6 The difference between this embodiment and Embodiment 2 is that the porous high-entropy alloy material is composed of Ti, Ta, Nb, Zr and Hf elements, and the atomic percentage of each element is 25:15:20:15:25. After calculation, 2.3≤(1.5[Ti]+2.4[Ta]+2.7[Nb]-2.1[Hf]) / [Zr]=5.

[0030] Testing revealed that the microstructure of the porous high-entropy alloy material prepared in this embodiment is a two-phase structure consisting of 87.7% BCC structure and 12.3% HCP structure, with a porosity of 21.1%, an average pore size of 15.3 µm, a room temperature compressive strength of 334 MPa, and an elastic modulus of 8.3 GPa.

[0031] Example 7 The difference between this embodiment and Embodiment 2 is that the particle size range of Ti, Ta, Nb, ZrH2 and Hf powders in step one is 0.5µm~1µm.

[0032] Testing revealed that the microstructure of the porous high-entropy alloy material prepared in this embodiment is a two-phase structure consisting of 93.2% BCC structure and 6.8% HCP structure, with a porosity of 34.2%, an average pore size of 22.5µm, a room temperature compressive strength of 241MPa, and an elastic modulus of 5.6GPa.

[0033] Example 8 The difference between this embodiment and Embodiment 2 is that the particle size range of Ti, Ta, Nb, ZrH2 and Hf powders in step one is 4µm~5µm.

[0034] Testing revealed that the microstructure of the porous high-entropy alloy material prepared in this embodiment is a two-phase structure consisting of 94.8% BCC structure and 5.2% HCP structure, with a porosity of 35.6%, an average pore size of 25.1µm, a room temperature compressive strength of 215MPa, and an elastic modulus of 5.1GPa.

[0035] Example 9 The difference between this embodiment and Embodiment 2 is that the particle size range of the stearic acid powder in step two is 80µm~120µm.

[0036] Testing revealed that the microstructure of the porous high-entropy alloy material prepared in this embodiment is a two-phase structure consisting of 92.7% BCC structure and 7.3% HCP structure, with a porosity of 38.3%, an average pore size of 32.6µm, a room temperature compressive strength of 185MPa, and an elastic modulus of 4.5GPa.

[0037] Example 10 The difference between this embodiment and Embodiment 2 is that the particle size range of the stearic acid powder in step two is 170µm~200µm.

[0038] Testing revealed that the microstructure of the porous high-entropy alloy material prepared in this embodiment is a two-phase structure consisting of 94.1% BCC structure and 5.9% HCP structure, with a porosity of 41.6%, an average pore size of 44.8µm, a room temperature compressive strength of 135MPa, and an elastic modulus of 3.8GPa.

[0039] Example 11 The difference between this embodiment and embodiment 2 is that the pressure of cold isostatic pressing in step 3 is 100 MPa, and the holding time is 1 min.

[0040] Testing revealed that the microstructure of the porous high-entropy alloy material prepared in this embodiment is a two-phase structure consisting of 92.5% BCC structure and 7.5% HCP structure, with a porosity of 36.6%, an average pore size of 25.8µm, a room temperature compressive strength of 208MPa, and an elastic modulus of 5.1GPa.

[0041] Example 12 The difference between this embodiment and embodiment 2 is that the pressure of cold isostatic pressing in step 3 is 300 MPa, and the holding time is 10 min.

[0042] Testing revealed that the microstructure of the porous high-entropy alloy material prepared in this embodiment is a two-phase structure consisting of 93.2% BCC structure and 6.8% HCP structure, with a porosity of 31.6%, an average pore size of 21.2µm, a room temperature compressive strength of 246MPa, and an elastic modulus of 5.6GPa.

[0043] Example 13 The difference between this embodiment and embodiment 2 is that in step four, the green blank from step three is heated, and then degreased at 200°C for 1 hour and pre-sintered at 700°C for 1 hour in sequence, and then cooled with the furnace to obtain a pre-sintered body.

[0044] Testing revealed that the microstructure of the porous high-entropy alloy material prepared in this embodiment is a two-phase structure consisting of 94.2% BCC structure and 5.8% HCP structure, with a porosity of 33.6%, an average pore size of 23.6µm, a room temperature compressive strength of 232MPa, and an elastic modulus of 5.4GPa.

[0045] Example 14 The difference between this embodiment and embodiment 2 is that in step four, the green blank from step three is heated, and then degreased at 500°C for 8 hours and pre-sintered at 1000°C for 5 hours in sequence, and then cooled with the furnace to obtain a pre-sintered body; Testing revealed that the microstructure of the porous high-entropy alloy material prepared in this embodiment is a two-phase structure consisting of 93.8% BCC structure and 6.2% HCP structure, with a porosity of 32.9%, an average pore size of 22.8µm, a room temperature compressive strength of 239MPa, and an elastic modulus of 5.4GPa.

[0046] Example 15 The difference between this embodiment and embodiment 2 is that in step five, the pre-sintered body from step four is heated to 1200°C and sintered for 1 hour, then cooled in the furnace to obtain a porous high-entropy alloy material.

[0047] Testing revealed that the microstructure of the porous high-entropy alloy material prepared in this embodiment is a two-phase structure consisting of 95.5% BCC structure and 4.5% HCP structure, with a porosity of 38.3%, an average pore size of 28.1µm, a room temperature compressive strength of 195MPa, and an elastic modulus of 4.6GPa.

[0048] Example 16 The difference between this embodiment and embodiment 2 is that in step five, the pre-sintered body from step four is heated to 1500°C and sintered for 5 hours, then cooled in the furnace to obtain a porous high-entropy alloy material.

[0049] Testing revealed that the microstructure of the porous high-entropy alloy material prepared in this embodiment is a two-phase structure consisting of 94.8% BCC structure and 5.2% HCP structure, with a porosity of 31.2%, an average pore size of 20.8µm, a room temperature compressive strength of 259MPa, and an elastic modulus of 5.7GPa.

[0050] Example 17 The difference between this embodiment and Embodiment 2 is that the porous high-entropy alloy material is composed of Ti, Ta, Nb, Zr and Hf elements, and the atomic percentage of each element is 10:27:25:23:15. After calculation, 2.3≤(1.5[Ti]+2.4[Ta]+2.7[Nb]-2.1[Hf]) / [Zr]≈5.035.

[0051] Testing revealed that the microstructure of the porous high-entropy alloy material prepared in this embodiment is a two-phase structure consisting of 98% BCC structure and 2% HCP structure, with a porosity of 37.1%, an average pore size of 26.3µm, a room temperature compressive strength of 201MPa, and an elastic modulus of 5.1GPa.

[0052] Example 18 The difference between this embodiment and Embodiment 2 is that the porous high-entropy alloy material is composed of Ti, Ta, Nb, Zr and Hf elements, and the atomic percentage of each element is 47:5:5:20:23. After calculation, 2.3≤(1.5[Ti]+2.4[Ta]+2.7[Nb]-2.1[Hf]) / [Zr]=2.385.

[0053] Testing revealed that the microstructure of the porous high-entropy alloy material prepared in this embodiment is a two-phase structure consisting of 70% BCC structure and 30% HCP structure, with a porosity of 29.5%, an average pore size of 18.3µm, a room temperature compressive strength of 282MPa, and an elastic modulus of 6.1GPa.

[0054] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A porous high-entropy alloy material, characterized in that, Composed of Ti, Ta, Nb, Zr, and Hf elements, with the atomic percentages of each element satisfying the following relationship: 2.3≤(1.5[Ti]+2.4[Ta]+2.7[Nb]-2.1[Hf]) / [Zr]≤5.1, this porous high-entropy alloy material has a microstructure consisting of a two-phase structure of 70%~98% BCC structure and 2%~30% HCP structure, a porosity of 0.5%~70%, an average pore size of 0.5µm~65µm, a room temperature compressive strength of 80MPa~2000MPa, and an elastic modulus of 2GPa~30GPa.

2. A method for preparing the porous high-entropy alloy material as described in claim 1, characterized in that, The method includes the following steps: Step 1: According to the composition ratio of the target product porous high-entropy alloy material, mix Ti, Ta, Nb, ZrH2 and Hf powders to obtain the first mixed powder; Step 2: Mix the first mixed powder obtained in Step 1 with stearic acid powder until homogeneous to obtain the second mixed powder; Step 3: The second mixed powder obtained in Step 2 is pressed into a green body by cold isostatic pressing; Step 4: Under an argon atmosphere, the green blank from Step 3 is heated, and then degreased and pre-sintered in sequence, and cooled with the furnace to obtain a pre-sintered body; Step 5: Under an argon atmosphere, the pre-sintered body from Step 4 is heated and sintered, then cooled in the furnace to obtain a porous high-entropy alloy material.

3. The method according to claim 2, characterized in that, The particle size range of the Ti, Ta, Nb, ZrH2 and Hf powders mentioned in step one is 0.5µm to 5µm.

4. The method according to claim 2, characterized in that, The particle size range of the stearic acid powder in step two is 5µm to 200µm, and the volume percentage of stearic acid powder in the second mixed powder is 0.1% to 80%.

5. The method according to claim 2, characterized in that, The pressure of the cold isostatic pressing in step three is 100MPa~300MPa, and the holding time is 1min~10min.

6. The method according to claim 2, characterized in that, The degreasing temperature in step four is 200℃~500℃, and the holding time is 1h~8h; the pre-sintering temperature is 700℃~1000℃, and the holding time is 1h~5h.

7. The method according to claim 2, characterized in that, The sintering temperature in step five is 1200℃~1500℃, and the holding time is 1h~5h.