FeCoNiCrMn高熵合金动态力学性能与微观结构

采用分离式霍普金森压杆研究了等原子比FeCoNiCrMn高熵合金的动态力学性能及其微观结构。结果表明, FeCoNiCrMn高熵合金的锯齿行为在高应变速率下表现出明显的应变率敏感性。高熵合金在高应变率下的屈服强度随应变率增加而显著增加。当真应变为3.07时, 真应力达到1 270 MPa, 此时FeCoNiCrMn高熵合金帽型样品出现剪切失稳现象, 并形成一条宽20 μm左右的剪切带。利用光学显微镜、电子探针显微分析仪和透射电子显微镜分析了高熵合金显微组织的演变, 发现在剪切带的边界处, 位错胞和孪生结构沿剪切方向高度拉长, 直径约为150 nm的超细等轴晶粒和纳米孪晶共同存在于剪切带的中心。

Dynamic Mechanical Properties and Microstructure of FeCoNiCrMn High Entropy Alloy

A split-Hopkinson pressure bar was used to study the dynamic mechanical properties and microstructure of equiatomic FeCoNiCrMn high entropy alloy. Results showed that the serration behavior of FeCoNiCrMn high entropy alloy is obviously sensitive to strain rate at high strain rates. The yield strength of high entropy alloys at high strain rates was increased significantly with the increasing of strain rate. When the true strain was 3.07, the true stress reached 1 270 MPa. Meanwhile, an unstable shear deformation occurred in the FeCoNiCrMn alloy hat-shaped sample, forming a shear band with 20 μm in width. The microstructure of high entropy alloy was analyzed with an optical microscope, electron probe microanalyzer and transmission electron microscope. It is found that dislocation cells and twin structures of the boundary in the shear band were elongated along the shear direction. Both ultrafine-equiaxed grains and nano-twins with a diameter of about 150 nm were found to be existed in the core of the shear band.