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CN-122007442-A - LPBF prepared high-strength high-toughness NiCoCr medium-entropy alloy and preparation process thereof

CN122007442ACN 122007442 ACN122007442 ACN 122007442ACN-122007442-A

Abstract

The invention discloses a LPBF-prepared high-strength high-toughness NiCoCr medium-entropy alloy and a preparation process thereof, and belongs to the technical field of metal materials and additive manufacturing. The preparation process includes preparing NiCoCr alloy powder through supersonic gas atomization to form Ti/Al enriched layer on the surface, forming with LPBF double energy fields, constructing continuous dislocation cytoskeleton with main forming laser, clustering high density dislocation and solute nanometer by auxiliary modulating laser, and final aging at 700-800 deg.c/1-2 h to induce precise nucleation of very small gamma' phase. The method prepares the extremely small precipitated phase of 10nm which is difficult to obtain by the entropy alloy in the traditional forging NiCoCr, solves the technical bottlenecks of insufficient dislocation cell stability, disordered nucleation of the reinforced phase and unbalanced toughness in the prior art, and the prepared alloy has excellent strength and toughness, simple and controllable process and obvious industrialization potential, and is suitable for severe service environments such as aerospace, high-end equipment and the like.

Inventors

  • ZHANG YONG
  • CHEN PENGPENG
  • ZHANG BOHOU
  • WU ZHIHAN
  • WANG DIE
  • SHEN JIAJIA
  • YUAN SHENGYUN

Assignees

  • 南京理工大学

Dates

Publication Date
20260512
Application Date
20260318

Claims (9)

  1. 1. The preparation process of the high-strength high-toughness NiCoCr medium-entropy alloy prepared by LPBF is characterized by comprising the following steps of: preparing NiCoCr alloy powder; step two, LPBF double energy fields are cooperatively formed to obtain a formed blank; and thirdly, performing short-time heat treatment on the formed blank.
  2. 2. The manufacturing process according to claim 1, wherein step one comprises the steps of: S1, raw material pretreatment, namely proportioning pure metal raw materials ：Ni 49.21at%、Co 24.71at%、Cr 15.10at%、Al 2.48at%、Ti 3.23at%、Mo 2.93at%、W 1.36at%、Nb 0.43at%、Ta 0.55at%, according to atomic percent, wherein the purity of the raw materials is more than or equal to 99.95at%, removing oxide scales from bulk raw materials, cutting into 8-12mm small blocks, cutting into 15-20 mm sections of filiform raw materials, and drying in a 120 ℃ vacuum drying box for 4 h; S2, vacuum induction smelting, namely adding the pretreated raw materials into a vacuum induction smelting furnace crucible, vacuumizing to be less than or equal to 5 multiplied by 10 -3 Pa, introducing argon to be 0.3MPa, heating to 1620 ℃ at 40 ℃ per min, preserving heat to 40 min, and stirring once every 8 min to obtain uniform alloy liquid; S3, performing supersonic gas atomization, namely introducing alloy liquid into an atomization chamber through a 6 mm guide pipe, adopting argon with the purity of more than or equal to 99.99% as an atomization medium, wherein the atomization pressure is 5.0-5.5 MPa, the pressure of the atomization chamber is 0.6 MPa, and crushing and cooling the alloy liquid to form spherical powder, wherein the atomization air flow speed reaches 680-850 m/S; S4, powder grading treatment, namely, screening out 15-53 mu m powder by a standard sieve with 150 meshes and 400 meshes after cyclone separation, and drying the powder in a vacuum drying box at 100 ℃ for 3 h to obtain NiCoCr alloy powder.
  3. 3. The preparation process according to claim 1, wherein the second step comprises the steps of: s01, niCoCr alloy powder pretreatment, namely drying NiCoCr alloy powder in a 120 ℃ vacuum drying box for 6 h; s02, controlling a forming atmosphere, namely vacuumizing a printing cabin, introducing argon, maintaining the oxygen content to be less than or equal to 30 ppm, and preheating a forming cylinder substrate to 100 ℃; S03, main forming laser scanning, namely setting power 280W, speed 850 mm/S, scanning interval 60 mu m and layer thickness 30 mu m, adopting a 6X 6 mm island scanning strategy, constructing a continuous dislocation cytoskeleton and capturing cell wall solutes, wherein the overlapping rate is 12%; s04, scanning by auxiliary modulation laser, namely, in-situ re-scanning in 30S after the main scanning of each layer is finished, wherein the power is 90W, the speed is 1600 mm/S, the defocus amount is +3.5 mm, and the clustering of high-density geometric necessary dislocation and solute nanometer is induced to form a metastable precursor structure.
  4. 4. The process according to claim 1, wherein the third step comprises the steps of placing the shaped blank in a box furnace, preserving heat at 700-800 ℃ for 1-2 h, and naturally cooling to room temperature to obtain the target alloy.
  5. 5. The process according to claim 3, wherein in S03, the cooling rate of the main forming laser scan is not less than 1X 10 4 K/S.
  6. 6. A LPBF-prepared high-strength high-toughness NiCoCr medium-entropy alloy obtained by a preparation process according to any one of claims 1 to 5.
  7. 7. The high-strength high-toughness NiCoCr medium-entropy alloy prepared by LPBF according to claim 6, wherein the alloy has a double-scale synergistic structure of dislocation cytoskeleton and extremely small gamma ' precipitated phases, wherein the dislocation cytoskeleton is of a continuous through submicron-scale structure, the average size is 450-500 nm, the geometric necessary dislocation density of cell walls is more than or equal to 1.8x10 11 m -2 , nano clustered precursors with the size of 5-10 nm are uniformly distributed on the cell walls, sites are provided for nucleation of gamma ' phases, the extremely small gamma ' precipitated phases are of an L1 2 ordered structure, and the average particle size is less than 10 nm and is coherent with a gamma matrix.
  8. 8. The high strength, high toughness NiCoCr medium entropy alloy according to claim 6, wherein the alloy has room temperature yield strength of 1284-1332 MPa, tensile strength of 1571-1641 MPa, elongation at break of 18.1-20.4% and plane strain fracture toughness KIC of 121-135mpa.m 1/2 .
  9. 9. Use of an entropy alloy in NiCoCr of high strength and high toughness prepared according to claim 6 in aerospace equipment, energy power equipment.

Description

LPBF prepared high-strength high-toughness NiCoCr medium-entropy alloy and preparation process thereof Technical Field The invention relates to a LPBF prepared high-strength high-toughness NiCoCr medium entropy alloy and a preparation process thereof, in particular to a LPBF prepared dislocation cell-minimum gamma' phase cooperative reinforcement NiCoCr medium entropy alloy and a preparation method thereof, which are particularly suitable for realizing cooperative optimization of alloy structure and performance by combining additive manufacturing and accurate structure regulation. Belonging to the technical field of metal material and additive manufacturing. Background The NiCoCr medium-entropy alloy is used as a face-centered cubic structure multi-principal element alloy, has excellent plasticity, fracture toughness and corrosion resistance, and has wide application prospect in the fields of high-end equipment such as aerospace, energy power and the like. The laser powder bed melting (LPBF) additive manufacturing technology can rapidly realize the direct manufacture of complex structural components by virtue of a discrete-stacking forming principle, and can form submicron dislocation cellular substructure by extremely rapid solidification (10 3-106 K/s) effect, thereby providing a good mechanical property foundation for materials. The entropy alloy in the conventional forging NiCoCr is difficult to obtain 10 nm extremely small gamma 'phase, and coarse gamma' can seriously affect the toughness of the material while improving the strength. However, the prior art still has a significant bottleneck in LPBF preparation and performance regulation of the entropy alloy in NiCoCr, and the coarsening behavior of gamma' is still difficult to control after aging treatment. The traditional gas atomization powder is of a uniform component structure, solute atoms are uniformly distributed, so that the dislocation cell walls lack of the LPBF formed dislocation cell skeleton to be strong in pertinence and insufficient in structural stability, the single laser scanning can only form a basic dislocation cell skeleton, the dislocation density of the cell walls is low, the effective enrichment of the solute atoms is not realized, dislocation cell deformation and the disorder of a strengthening phase are easy to occur in the subsequent heat treatment process, the precise matching of the structure and the strengthening phase is difficult to realize, the conventional strengthening scheme is easy to cause strength and toughness unbalance, and the severe requirements of high-end equipment on the comprehensive performance of materials cannot be met. Therefore, developing a preparation method for realizing dislocation cell stabilization and strengthening phase precise nucleation matching through full-process innovation becomes a key for promoting the engineering application of the entropy alloy in NiCoCr. Disclosure of Invention Aiming at the technical defects of insufficient dislocation cell stability, disordered strengthening phase nucleation and unbalanced toughness of the entropy alloy in NiCoCr in the prior art, the invention provides a preparation method of the entropy alloy in NiCoCr with cooperative strengthening of dislocation cell-minimum gamma' phase prepared by LPBF, which comprises the steps of constructing a stable dislocation cell skeleton and solute clustering precursor through full chain innovation of powder preparation, forming process and heat treatment, and inducing precise nucleation of strengthening phase through heat treatment, so that excellent toughness of the material is realized. Meanwhile, the invention provides the high-strength high-toughness NiCoCr medium-entropy alloy prepared by LPBF, which has a dislocation cytoskeleton-extremely small gamma' precipitated phase double-scale cooperative reinforcement structure. Meanwhile, the invention provides application of the high-strength high-toughness NiCoCr entropy alloy prepared by LPBF in aerospace equipment and energy power equipment. In order to solve the technical problems, the invention adopts the following technical scheme: A preparation process of an entropy alloy in NiCoCr with high strength and high toughness, which is prepared by LPBF, comprises the following steps: 1. the preparation of the powder comprises constructing a Ti/Al element enriched layer on the surface of the powder by adopting a supersonic gas atomization technology. The design solves the problem of insufficient dislocation cell stability caused by the traditional uniform component powder from the source, and provides a natural component basis for enrichment of cell wall solutes and nucleation of strengthening phases after subsequent forming. The LPBF double energy field collaborative forming comprises the steps of designing a collaborative scanning mode of 'main forming laser and auxiliary modulating laser', rapidly constructing a continuous dislocation cytoskeleton by the main energ