A rare-earth cerium microalloyed high-strength, high-toughness, high-entropy alloy material and its preparation method

Abstract

This invention discloses a rare-earth cerium microalloyed high-strength and high-toughness high-entropy alloy material and its preparation method, belonging to the technical field of rare-earth alloy new materials. The method uses a FeCoCrNiMn high-entropy alloy with an atomic ratio of 1:1:1:1:1 as the matrix, adding 0.01%–0.1% by mass of rare-earth Ce; the alloy is then cast into ingots under vacuum induction melting and circulating water cooling; subsequently, the ingots undergo homogenization annealing, secondary cold rolling, and tertiary annealing to obtain the rare-earth cerium microalloyed high-entropy alloy material. This invention significantly improves the strength and toughness of the alloy through rare-earth cerium microalloying combined with multi-stage cold rolling and annealing processes. The resulting high-entropy alloy exhibits a maximum increase in yield strength of 127 MPa, a maximum increase in tensile strength of 164 MPa, and an increase in fracture strain rate of over 2%. The process of this invention is stable, simple to operate, and suitable for large-scale production.

Description

Technical Field

[0001] This invention relates to the field of rare earth alloy new materials technology, specifically to a high-strength, high-toughness, high-entropy alloy material with rare earth cerium microalloying and its preparation method. Background Technology

[0002] High-entropy alloys (HEAs), also known as multi-principal element alloys, represent a breakthrough in traditional alloy design logic. They abandon the single-element design approach centered on mixing enthalpy and relying on one or two principal elements, instead prioritizing high configurational entropy to construct novel multi-principal element metallic material systems. Typically, HEAs consist of five or more elements, with each principal element comprising 5% to 35% of the total atoms. This multi-element synergy breaks the limitations of traditional alloy composition. From a materials design perspective, HEAs significantly expand the selection and combination space of elements. Compared to the single-principal or dual-principal element schemes of traditional alloys, the number of alloying elements and combinations available for selection in the periodic table increases exponentially, fully releasing the resource potential of the periodic table in materials design. Therefore, HEAs are not only an innovative carrier for developing high-performance metallic materials but also a new design concept that maximizes the potential of alloy performance. The unique characteristics exhibited by HEAs are summarized into four distinct effects: the high-entropy effect, the lattice distortion effect, the slow diffusion effect, and the "cocktail" effect.

[0003] Among numerous high-entropy alloy systems, FeCoCrNiMn (Cantor alloy) has attracted much attention due to its excellent ductility and good phase stability. However, although this alloy exhibits excellent ductility at room temperature, its strength is relatively low, which has become a major factor limiting its future engineering applications. Therefore, how to resolve the contradiction between strength and ductility, and improve the strength of FeCoCrNiMn high-entropy alloys while ensuring good ductility, thereby obtaining an excellent strength-toughness balance, is currently the main research direction for high-entropy alloys in this system.

[0004] Essentially, the key to improving the strength-toughness balance of metallic materials lies in regulating and optimizing the "strengthening" and "softening" behaviors during material processing, preparation, and service, thereby coordinating and improving the balance between "dynamic" and "static" processes during plastic deformation, represented by dislocation slip or twinning mechanisms. Rare earth cerium (Ce) plays a significant role in synergistically regulating recrystallization softening and precipitation strengthening in FeCoCrNiMn high-entropy alloys. The Bayan Obo mine in Inner Mongolia Autonomous Region contains high abundance, large reserves, and relatively inexpensive rare earth cerium, making it a valuable resource to fully utilize. Therefore, the microalloying of rare earth cerium has great potential for regulating the strength and toughness of FeCoCrNiMn high-entropy alloys. Currently, alloys prepared using the FeCoCrNiMn high-entropy alloy preparation process generally suffer from a significant decrease in plasticity along with increased strength; that is, the poor strength-toughness balance remains a major bottleneck affecting the widespread application of this alloy. Summary of the Invention

[0005] The present invention aims to provide a rare earth cerium microalloyed high strength and toughness high entropy alloy material and its preparation method, so as to solve the technical problems of the significant decrease in plasticity and poor strength and toughness combination of existing FeCoCrNiMn high entropy alloys when the strength is improved.

[0006] The technical solution adopted in this invention is as follows:

[0007] A method for preparing a rare-earth cerium microalloyed high-strength, high-toughness, high-entropy alloy material includes the following steps:

[0008] (1) Composition design: A high-entropy alloy composed of five elements, Fe, Co, Cr, Ni and Mn with an atomic ratio of 1:1:1:1:1, is used as the matrix, and rare earth element Ce with a total alloy mass percentage of 0.01% to 0.1% is added to it;

[0009] (2) Alloy smelting and casting: A vacuum induction furnace is used to melt the metal or alloy raw materials of Fe, Co, Cr, Ni and Mn into liquid state. Then, metal Ce or Ce-Fe alloy is added to the melt. After holding the temperature for 1 min to 3 min, the alloy melt is cast into the cast iron mold. Before the melt is cast, the circulating water around the cast iron ingot mold is turned on to accelerate the cooling until the alloy melt is completely solidified into an alloy ingot.

[0010] (3) Homogenization treatment: The alloy ingot is placed in a tube furnace under the protection of high-purity argon gas and kept at 1100 ℃~1200 ℃ for 6 h~12 h;

[0011] (4) Cold rolling in one step: After the surface of the homogenized alloy ingot is polished to a bright finish and free of visible defects, it is cold rolled at room temperature with a reduction rate of 75% to 85%;

[0012] (5) First annealing: The cold-rolled high-entropy alloy plate is annealed at a holding temperature of 500 ℃~650℃ and a holding time of 1 min~10 min, so that fine and dispersed local chemically ordered structures and second phase particles are formed in the alloy.

[0013] (6) Secondary annealing: The high-entropy alloy cold-rolled sheet is annealed again at a holding temperature of 900 ℃~950 ℃ and a holding time of 5 s~60 s to allow the alloy matrix to recrystallize for the first time and refine the grains.

[0014] (7) Secondary cold rolling: The high-entropy alloy cold-rolled sheet is cold-rolled at room temperature with a reduction rate of 80% to 90%;

[0015] (8) Third annealing: The high entropy alloy cold-rolled plate is annealed for the third time at a temperature of 900 ℃~950 ℃ and a holding time of 5 s~30 s, so that the alloy matrix undergoes a second recrystallization, further refining the grains, thus completing the preparation process.

[0016] The content of impurity elements in the metal or alloy raw materials mentioned in step (2) should be ≤0.1%, and the size of the added metal Ce or Ce-Fe alloy should be a cube with a length, width and height in the range of 10 mm to 15 mm.

[0017] Before use, the inner wall of the cast iron mold described in step (2) should be uniformly coated with a mixture of lanthanum oxide, cerium oxide or yttrium oxide and anhydrous ethanol and dried to facilitate the demolding of the alloy ingot after casting. The ratio of oxide to anhydrous ethanol is 0.5 to 1 g: 10 mL.

[0018] In the annealing process described in steps (5), (6) and (8), after each annealing and heat preservation is completed, the sample is quickly transferred to water to cool to room temperature.

[0019] A rare-earth cerium microalloyed high-strength, high-toughness, high-entropy alloy material is prepared using the method described above.

[0020] This invention achieves synergistic effects of multiple strengthening mechanisms by adding trace amounts of rare earth cerium to FeCoCrNiMn high-entropy alloys and employing a process route of low-temperature short-time annealing, high-temperature ultra-short-time recrystallization annealing, secondary cold rolling, and ultra-short-time recrystallization annealing. This results in the synergistic enhancement of fine-grain strengthening, precipitation strengthening, dislocation strengthening, and local chemically ordered strengthening.

[0021] The beneficial effects of this invention:

[0022] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0023] (1) Significantly Improved Strength and Toughness: By adding trace amounts of rare earth cerium and combining it with multi-step heat treatment and cold deformation processes, the FeCoCrNiMn high-entropy alloy prepared by this invention achieves significant improvements in both strength and ductility while maintaining good plasticity. Example data shows that, compared with the control alloy without added rare earth cerium, the alloy of this invention exhibits a maximum increase in yield strength of 127 MPa, a maximum increase in tensile strength of 164 MPa, and an increase in fracture strain rate of over 2%, effectively overcoming the problem of the inherent contradiction between strength and plasticity in traditional FeCoCrNiMn high-entropy alloys, making it difficult to simultaneously improve both.

[0024] (2) Synergistic optimization of microstructure: The present invention achieves the synergistic effect of multiple strengthening mechanisms in the alloy through a unique process route of “low temperature short time annealing + high temperature ultra-short time recrystallization annealing + secondary cold rolling + final ultra-short time recrystallization annealing”.

[0025] Specifically: First annealing (500–650 °C, 1–10 min) promotes the formation of fine, dispersed locally chemically ordered (LCO) structures and nanoscale second-phase particles, providing significant precipitation strengthening and order strengthening; second annealing (900–950 °C, 5–60 s) triggers the first recrystallization, initially refining the grains; second cold rolling introduces high-density dislocations and deformation energy storage; third annealing (900–950 °C, 5–30 s) triggers the second recrystallization, further refining the grains while retaining some substructures. Ultimately, a multiphase microstructure composed of a fine-grained matrix, dispersed nanoprecipitates, and locally chemically ordered regions is obtained, achieving a synergistic effect of grain refinement strengthening, precipitation strengthening, dislocation strengthening, and locally chemically ordered strengthening.

[0026] (3) Multiple effects of rare earth cerium: The addition of trace rare earth cerium, on the one hand, during the solidification process, Ce atoms are enriched at the solid-liquid interface, reducing the distribution kinetics of solute atoms at the solid-liquid interface and refining the as-cast structure; on the other hand, Ce elements are segregated at grain boundaries and dislocations, inhibiting grain coarsening during recrystallization and promoting the formation of a uniform and fine recrystallized structure, thereby simultaneously improving strength and plasticity.

[0027] (4) Stable process and suitable for large-scale production: The process technology adopted in this invention has low equipment requirements, wide operating window (such as a wide range of annealing temperature and time), and is easy to realize industrial mass production, with good market application prospects. Attached Figure Description

[0028] Figure 1 The image shows a comparison of the tensile stress-strain rate curves of the rare-earth cerium microalloyed high-entropy alloy prepared in Example 1 and the control high-entropy alloy without cerium.

[0029] Figure 2This is a comparison of the tensile stress-strain rate curves of the rare earth cerium microalloyed high-entropy alloy prepared in Example 2 and the control high-entropy alloy without cerium. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to specific experimental examples. The embodiments are only used to explain the present invention and are not intended to limit the scope of protection of the present invention.

[0031] Example 1

[0032] This embodiment provides a method for preparing a rare-earth cerium microalloyed high-strength, high-toughness, high-entropy alloy material, the specific steps of which are as follows:

[0033] (1) Composition design: Fe, Co, Cr, Ni and Mn in an equiatomic ratio (1:1:1:1:1) are used as the matrix, and rare earth Ce elements accounting for 0.03% of the total alloy mass are added.

[0034] (2) Alloy smelting and casting: A vacuum induction furnace is used. First, Fe, Co, Cr, Ni, and Mn metal raw materials (purity ≥99.9%, total impurity element content ≤0.1%) are melted into a liquid state. Then, Ce-Fe alloy with 10% Ce content is added to the melt. The added Ce-Fe alloy is a block material with a length, width, and height of 10~15 mm. After holding at the temperature for 2 min, the alloy melt is poured into a cast iron mold. Before the melt is poured, the circulating water around the cast iron ingot mold is turned on to accelerate cooling until the alloy melt is completely solidified into an alloy ingot. Before use, the inner wall of the cast iron mold is uniformly coated with a mixture of yttrium oxide and anhydrous ethanol and dried (the ratio of yttrium oxide to anhydrous ethanol is 0.5 g: 10 mL) to facilitate demolding.

[0035] (3) Homogenization treatment: The above alloy ingots are placed in a tube furnace under the protection of high-purity argon gas and kept at 1150 ℃ for 8 hours.

[0036] (4) Cold rolling: After the surface of the homogenized alloy ingot is polished to a bright finish and free of visible defects, it is cold rolled at room temperature with a reduction rate of 80%.

[0037] (5) First annealing: The cold-rolled high-entropy alloy plate was annealed in a tube furnace at a holding temperature of 550°C for 5 min to form a fine, dispersed local chemically ordered structure and second-phase particles in the high-entropy alloy. After the annealing holding was completed, the sample was quickly transferred to water to cool to room temperature.

[0038] (6) Secondary annealing: The above-mentioned high-entropy alloy cold-rolled sheet was annealed again at a holding temperature of 920 ℃ for 10 s to allow the high-entropy alloy matrix to recrystallize for the first time and refine the grains. After the annealing holding was completed, the sample was quickly transferred to water to cool to room temperature.

[0039] (7) Secondary cold rolling: The above-mentioned high-entropy alloy cold-rolled sheet is cold-rolled at room temperature with a reduction rate of 85%.

[0040] (8) Third annealing: The above-mentioned high-entropy alloy cold-rolled sheet is subjected to a third annealing treatment at a holding temperature of 930 ℃ for 15 s, so that the high-entropy alloy matrix undergoes a second recrystallization, further refining the grains. After the annealing holding is completed, the sample is quickly transferred to water to cool to room temperature, and the finished product is obtained.

[0041] Comparative Example 1: To facilitate the evaluation of the performance of the product of the present invention, a control alloy without the addition of rare earth cerium was set up simultaneously: that is, the matrix composition is FeCoCrNiMn with equal atomic ratio and no Ce is added, and the other preparation process parameters are the same as those in Example 1.

[0042] Performance testing:

[0043] The results were obtained through room temperature tensile testing. Figure 1 As shown, the rare-earth cerium microalloyed FeCoCrNiMn high-entropy alloy prepared in Example 1 has a yield strength of 1140 MPa, a tensile strength of 1240 MPa, and a fracture strain rate of 34.6%. The control alloy's FeCoCrNiMn high-entropy alloy has a yield strength of 1013 MPa, a tensile stress of 1076 MPa, and a fracture strain rate of 32.6%. Compared to the control alloy, the alloy in Example 1 shows an increase of 127 MPa in yield strength, 164 MPa in tensile stress, and 2.0% in fracture strain rate.

[0044] Example 2

[0045] A method for preparing a rare-earth cerium microalloyed high-strength, high-toughness, high-entropy alloy material, the specific steps of which are as follows:

[0046] (1) Composition design: Fe, Co, Cr, Ni and Mn in an equiatomic ratio (1:1:1:1:1) are used as the matrix, and rare earth element Ce is added at 0.075% of the total alloy mass.

[0047] (2) Alloy smelting and casting: A vacuum induction furnace is used to first melt Fe, Co, Cr, Ni, and Mn metal raw materials (purity ≥99.9%, impurity content ≤0.1%) into a liquid state, and then add Ce-Fe alloy with a Ce content of 30% to the melt. The added Ce-Fe alloy is in the form of square material with a length, width, and height of 10~15 mm. After holding at the temperature for 1.5 min, the alloy melt is poured into a cast iron mold. Before the melt is poured, the circulating water wrapped around the cast iron ingot mold is turned on to accelerate cooling until the alloy melt is completely solidified into an alloy ingot. Before use, the inner wall of the cast iron mold is uniformly coated with a mixture of cerium oxide and anhydrous ethanol (the ratio of cerium oxide to anhydrous ethanol is 0.7 g:10 mL) and dried.

[0048] (3) Homogenization treatment: The above alloy ingots are placed in a tube furnace under the protection of high-purity argon gas and kept at 1100 ℃ for 10 h.

[0049] (4) Cold rolling: After the surface of the homogenized alloy ingot is polished to a bright finish and free of visible defects, it is cold rolled at room temperature with a reduction rate of 85%.

[0050] (5) First annealing: The cold-rolled high-entropy alloy plate was annealed at a holding temperature of 620 °C for 8 min to form a fine, dispersed local chemically ordered structure and second-phase particles in the high-entropy alloy. After the annealing holding was completed, the sample was quickly transferred to water to cool to room temperature.

[0051] (6) Secondary annealing: The above-mentioned high-entropy alloy cold-rolled sheet was annealed again at a holding temperature of 930 ℃ for 10 s to allow the high-entropy alloy matrix to recrystallize for the first time and refine the grains. After the annealing holding was completed, the sample was quickly transferred to water to cool to room temperature.

[0052] (7) Secondary cold rolling: The above-mentioned high-entropy alloy cold-rolled sheet is cold-rolled at room temperature with a reduction rate of 80%.

[0053] (8) Third annealing: The above-mentioned high-entropy alloy cold-rolled sheet is subjected to a third annealing treatment at a holding temperature of 910 ℃ for 20 s, so that the high-entropy alloy matrix undergoes a second recrystallization, further refining the grains. After the annealing holding is completed, the sample is quickly transferred to water to cool to room temperature, and the finished product is obtained.

[0054] Comparative Example 2: To facilitate the evaluation of the performance of the product of the present invention, a control alloy without the addition of rare earth cerium was set up simultaneously: that is, the matrix composition is FeCoCrNiMn with equal atomic ratio and no Ce is added, and the other preparation process parameters are the same as those in Example 2.

[0055] Performance testing:

[0056] The results were obtained through room temperature tensile testing. Figure 2 As shown, the rare-earth cerium microalloyed FeCoCrNiMn high-entropy alloy prepared in Example 2 has a yield strength of 1067 MPa, a tensile strength of 1120 MPa, and a fracture strain rate of 22.9%. The control alloy's FeCoCrNiMn high-entropy alloy has a yield strength of 998 MPa, a tensile stress of 1020 MPa, and a fracture strain rate of 20.6%. Compared to the control alloy, the alloy in this example shows an increase of 69 MPa in yield strength, 100 MPa in tensile stress, and 2.3% in fracture strain rate.

Claims

1. A method for preparing a rare-earth cerium microalloyed high-strength, high-toughness, high-entropy alloy material, characterized in that, Includes the following steps: (1) Composition design: A high-entropy alloy composed of five elements, Fe, Co, Cr, Ni and Mn with an atomic ratio of 1:1:1:1:1, is used as the matrix, and rare earth element Ce with a total alloy mass percentage of 0.01% to 0.1% is added to it; (2) Alloy smelting and casting: A vacuum induction furnace is used to melt the metal or alloy raw materials of Fe, Co, Cr, Ni and Mn into liquid state. Then, metal Ce or Ce-Fe alloy is added to the melt. After holding the temperature for 1 min to 3 min, the alloy melt is cast into the cast iron mold. Before the melt is cast, the circulating water around the cast iron ingot mold is turned on to accelerate the cooling until the alloy melt is completely solidified into an alloy ingot. (3) Homogenization treatment: The alloy ingot is placed in a tube furnace under the protection of high-purity argon gas and kept at 1100 ℃~1200 ℃ for 6 h~12 h; (4) Cold rolling in one step: After the surface of the homogenized alloy ingot is polished to a bright finish and free of visible defects, it is cold rolled at room temperature with a reduction rate of 75% to 85%; (5) First annealing: The cold-rolled high-entropy alloy plate is annealed at a holding temperature of 500 ℃~650 ℃ and a holding time of 1 min~10 min, so that fine and dispersed local chemically ordered structures and second phase particles are formed in the alloy. (6) Secondary annealing: The high-entropy alloy cold-rolled sheet is annealed again at a holding temperature of 900 ℃~950℃ for 5 s~60 s to allow the alloy matrix to recrystallize for the first time and refine the grains. (7) Secondary cold rolling: The high-entropy alloy cold-rolled sheet is cold-rolled at room temperature with a reduction rate of 80% to 90%; (8) Third annealing: The high entropy alloy cold-rolled plate is annealed for the third time. The holding temperature is 900 ℃~950 ℃ and the holding time is 5 s~30 s, so that the alloy matrix undergoes a second recrystallization, further refining the grains, thus completing the preparation process.

2. The preparation method according to claim 1, characterized in that, The content of impurity elements in the metal or alloy raw materials mentioned in step (2) should be ≤0.1%, and the size of the added metal Ce or Ce-Fe alloy should be a cube with a length, width and height in the range of 10 mm to 15 mm.

3. The preparation method according to claim 1, characterized in that, Before use, the inner wall of the cast iron mold described in step (2) should be uniformly coated with a mixture of lanthanum oxide, cerium oxide or yttrium oxide and anhydrous ethanol and dried to facilitate the demolding of the alloy ingot after casting. The ratio of oxide to anhydrous ethanol is 0.5 to 1 g: 10 mL.

4. The preparation method according to claim 1, characterized in that, In the annealing process described in steps (5), (6) and (8), after each annealing and heat preservation is completed, the sample is quickly transferred to water to cool to room temperature.

5. A rare-earth cerium microalloyed high-strength, high-toughness, high-entropy alloy material, characterized in that, It is prepared by any one of claims 1-4.

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