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CN-121988751-A - Low-fault-energy high-entropy alloy and preparation method thereof

CN121988751ACN 121988751 ACN121988751 ACN 121988751ACN-121988751-A

Abstract

The invention discloses a preparation method of low-fault energy high-entropy alloy, which comprises the following steps of (1) weighing spherical CoCrNiAl alloy and Co, cr, ni, ti powder according to stoichiometric Al a Ti b Ni c Co d Cr e , (2) putting the weighed powder into a ball milling tank for ball milling, uniformly mixing the powder, then drying, sieving, drying and storing, (3) selecting 304L stainless steel as a base material, polishing the surface of the base material by using a sand mill to remove surface oxide skin until a bright surface is exposed, and (4) placing the dried powder into a powder feeding tank in a laser system by using high-purity Ar gas, and carrying out melting and stacking on the powder by using a circular spot laser head for layer-by-layer continuous deposition. The initiation and the extension of cracks in the laser additive manufacturing are inhibited by reducing the stacking fault energy of a high-entropy alloy system, and a large amount of coherent L12 phases can be separated out in situ, so that the high-entropy alloy has excellent mechanical properties at normal temperature.

Inventors

  • LIU QIBIN
  • Liao Tianhai
  • GUO YAXIONG
  • WANG FANGPING
  • SHANG XIAOJUAN

Assignees

  • 贵州大学
  • 贵阳职业技术学院
  • 贵州交通职业大学

Dates

Publication Date
20260508
Application Date
20260126

Claims (10)

  1. 1. The preparation method of the low-fault-energy high-entropy alloy is characterized by comprising the following steps of: (1) Weighing spherical CoCrNiAl alloy and Co, cr, ni, ti powder according to a stoichiometric formula Al a Ti b Ni c Co d Cr e , wherein a and b are 6.25 (at.%), c is 25-50 (at.%), d is 25-50 (at.%), and e is 12.5 (at.%); (2) Placing the weighed powder into a ball milling tank for ball milling to ensure that the powder is uniformly mixed, and then drying, sieving, drying and preserving; (3) Selecting 304L stainless steel as a base material, polishing the surface of the base material to remove surface oxide skin until a bright surface is exposed; (4) And (3) placing the dried powder in a powder feeding tank in a laser system by adopting a laser directional energy deposition method, and feeding the powder to a circular spot laser head by using high-purity Ar gas for melting and stacking, and continuously depositing layer by layer.
  2. 2. The method for preparing a low-stacking fault energy high-entropy alloy according to claim 1, wherein the stoichiometric formula is Al 6.25 Ti 6.25 Ni 50 Co 25 Cr 12.5 , al 6.25 Ti 6.25 Ni 37.5 Co 37.5 Cr 12.5 or Al 6.25 Ti 6.25 Ni 25 Co 50 Cr 12.5 .
  3. 3. The method for preparing low-stacking fault energy high-entropy alloy according to claim 1, wherein the grain size of CoCrNiAl, ti, ni, co, cr powder is 45-105 μm, and the purity is not less than 99.5%.
  4. 4. The method for preparing the low-stacking fault energy high-entropy alloy according to any one of claims 1 to 3, wherein the ball milling parameters are ball milling parameters, the ball milling speed is 200-300rpm/min, the ball milling speed is 1h in forward rotation and 1h in reverse rotation, the intermediate interval is 300s, and after ball milling, the mixed powder is dried in a vacuum drying oven to remove surface moisture.
  5. 5. The method for preparing a low-stacking fault energy high-entropy alloy according to claim 4, wherein the alloy is sieved through a 100-200 mesh sieve.
  6. 6. The method for preparing the low-fault-energy high-entropy alloy according to claim 5, wherein in the step (3), oil stains on the surface of the 304L stainless steel are cleaned by alcohol after polishing.
  7. 7. The method of manufacturing a low-stacking fault energy high-entropy alloy according to claim 6, wherein the type of the laser is RC-LMS-6000-R fiber laser.
  8. 8. The method of producing a low-stacking fault energy high-entropy alloy according to claim 7, wherein the laser energy density is 18.75-35J/mm 2 .
  9. 9. The method for preparing the low-stacking fault energy high-entropy alloy according to claim 8, wherein the laser parameters are laser power P=950W, scanning speed v=780 mm/min, Z-axis lifting speed is 0.3-mm circular spot diameter 3mm for each layer, and powder filling speed is 2r/min.
  10. 10. A low-stacking fault energy high-entropy alloy prepared by the method for preparing a low-stacking fault energy high-entropy alloy according to any one of claims 1 to 9.

Description

Low-fault-energy high-entropy alloy and preparation method thereof Technical Field The invention relates to the technical field of high-entropy alloy, in particular to a low-fault-energy high-entropy alloy and a preparation method thereof. Background Laser additive manufacturing technology is leading a revolution in the metal working field with its unique advantages in terms of manufacturing complex geometries and achieving ultra fine grain microstructures. Meanwhile, the multi-principal element high-entropy alloy is used as a new material breaking through the traditional design concept, and has great potential in extreme environment applications such as aerospace, energy chemical industry and the like due to the excellent strength, corrosion resistance and high/low temperature performance. The laser additive manufacturing technology is applied to the forming of the high-entropy alloy, and the advantages of the laser additive manufacturing technology and the high-entropy alloy can be combined theoretically, so that a brand new path is opened for manufacturing high-performance and structurally integrated key parts. However, this ideal path faces a serious common challenge in that microcracks are very easily formed during additive manufacturing, severely compromising the integrity, reliability and mechanical properties of the component. The crack problem has become one of the core bottlenecks that restrict the laser additive manufacturing of high-entropy alloys to engineering applications. The essence of laser additive manufacturing is an extremely unbalanced rapid fusing and complex thermal cycling process. The rapid scanning of the laser beam causes the material to undergo intense and localized heating and cooling, resulting in extremely high temperature gradients and cooling rates (up to 10 3-108 K/s). Uncoordinated thermal shrinkage (thermal stress) and phase change volume change (phase change stress) between different regions of the material are "frozen" inside the component, creating significant residual tensile stress. When the local stress exceeds the strength limit or crack propagation resistance of the material, the crack initiates and propagates. And unbalanced solidification forms tissue features such as fine cellular structure, high dislocation density, element segregation, etc. These structures, although potentially providing strengthening effects, may also become stress concentration points or brittle paths, especially along columnar grain boundaries or pool boundaries, promoting the generation of thermal cracks (solidification cracking) or solid state cracking. Studies have shown that many high entropy alloy systems, including classical FeCoCrNi systems and refractory high entropy alloys, have a prevalent crack susceptibility in the LPBF process, in amounts far beyond the ranges reported in the published literature. These cracks not only reduce the compactness and mechanical properties of the part, but also pose a fatal threat to its fatigue life and dynamic reliability. To address this challenge, researchers have proposed solutions from a number of angles, including mainly optimizing heat input and temperature field distribution to reduce residual stress by adjusting laser power, scan speed, scan strategy, etc. However, this method has limited effectiveness on materials with high intrinsic crack sensitivity of the alloy, and has narrow optimization window and poor universality. Developing new alloys that are specifically adapted for additive manufacturing conditions. For example, by adding trace amounts of carbon (C) or the like to strengthen grain boundaries and improve the bonding force of the grain boundaries, thereby suppressing grain boundary cracking, or by inducing dissolution of a second phase by thermal cycle of additive manufacturing, modifying the matrix composition to reduce the stacking fault energy, and promoting twinning plasticization. In recent years, a strategy based on the physical nature of material deformation has received high attention, namely, the regulation of the stacking fault energy of alloys. The stacking fault energy is the energy required for generating unit area fault in the crystal, and deeply influences the plastic deformation mechanisms such as dislocation slip, cross slip, twinning, martensitic transformation and the like. In conventional high-fault-energy materials, dislocation is prone to cross-slip and climb, forming entanglement or cellular structures. Under the action of thermal stress of additive manufacturing, stress is easily concentrated in local areas such as dislocation cell walls, and finally energy is released in a mode of initiating microcracks, so that cracking is caused. Conversely, lowering the stacking fault energy may cause the material to preferentially coordinate strain in deformation (including deformation caused by thermal stress) in the manner of planar slip, forming stacking faults, producing mechanical twins, or inducing epsilon-ma