Achieving strength-ductility synergy of spark plasma sintered (CoCrNi)94Al3Ti3 medium-entropy alloy via post-sintering in-situ precipitation treatment

作者：Shifeng Luo, Nan Wang, Yan Wang, Xiang Li, Xiaogang Fang, Hongwei Zhou, Jieming Chen, Xinyu Yang, Jiuxing Zhang · 发表于：Journal of Materials Research and Technology · 年份：2024 · DOI：10.1016/j.jmrt.2024.09.090 · 被引用次数：8 · 研究领域：High Entropy Alloys Studies、High-Temperature Coating Behaviors、Advanced materials and composites

The single-phase face-centered cubic medium-entropy alloys (MEAs) normally have coarse grains in as-cast state, which exhibit insufficient strength for engineering applications. Here, a superior tensile strength-ductility synergy in a fine grained (CoCrNi) 94 Al 3 Ti 3 MEA hardened by nanoscale L1 2 precipitates was fabricated by spark plasma sintering (SPS) and post-sintering in - situ precipitation treatment. The SPSed MEAs have a fine grain size of ⁓ 5 μm, and a high number density of L1 2 precipitates form after in - situ annealing within the SPS machine. A high tensile yield strength of 1141 MPa with an adequate elongation to fracture of 25.8% was achieved in (CoCrNi) 94 Al 3 Ti 3 MEA after annealing at 700 °C for 4 h. Electron backscattered diffraction and transmission electron microscopy characterizations indicate that the superior mechanical properties mainly originate from fine grains and the coherent spherical L1 2 precipitates. The dislocation slips and stacking faults prevail in all SPSed MEAs during tensile deformation, while extra Lomer-Cottrell locks are observed in annealed MEAs. The deformation twinning is absent in these precipitation-hardened MEAs with a low stacking fault energy, which may be attributed to the fine grains and numerous nanoscale L1 2 precipitates. This study not only confirms the effectiveness of powder metallurgy when sintering and precipitation are combined in - situ during the SPS cycle, but also provide guidance for the microstructure r...