沉淀强化对CoCrFeNiTi0.2多相高熵合金动态力学性能的影响

    Effect of Precipitation Strengthening on Dynamic Mechanical Properties of CoCrFeNiTi0.2 Multiphase High Entropy Alloy

    • 摘要: 采用真空感应熔炼(VIM)和特殊的热加工工艺制备富含两种沉淀析出相的CoCrFeNiTi0.2高熵合金,通过SEM、XRD、EDS测试方法观察合金变形前后的组织、结构,并进行静、动态压缩对照试验。结果表明:晶内析出与FCC固溶体共格的L12纳米沉淀相粒子,晶界处偏析粗大且不规则的片状HCP相粒子。该合金具有良好的塑性,变形过程中表现显著的加工硬化特点,动态加载中出现动态应变时效产生的PLC锯齿屈服强化。准静态压缩下,弹性模量约为7.23 GPa,没有明显屈服阶段。当应变率由500 s-1变化到2000 s-1时,其屈服强度从670 MPa上升到1005 MPa,弹性模量由30.43GPa增加到87.62 GPa。其组织表现为由晶界衍生的大量空洞转变成绝热剪切导致的脆性撕裂,晶内伴随着树枝晶的产生。

       

      Abstract: CoCrFeNiTi0.2 high-entropy alloy being rich in two precipitation phases was prepared by vacuum induction melting(VIM) and special hot working process, and the microstructure and structure of the alloy before and after deformation were observed by SEM, XRD and EDS test methods, the static and dynamic compression contrast tests were also conducted.The results show that the L12 nanometer precipitated particles of FCC solid solution are precipitated in the grains, and the coarse and irregular lamellar HCP particles are separated at the grain boundary. The alloy has good plasticity, showing significant work hardening characteristics during deformation, and PLC sawtooth yield strengthen is generated by dynamic strain aging during dynamic loading. Under quasi-static compression, the elastic modulus is about 7.23 GPa and there is no obvious yield phase. When the strain rate changes from 500 s-1 to 2000 s-1, the yield strength increases from 670 MPa to 1005 MPa, and the elastic modulus increases from 30.43 GPa to 87.62 GPa. The microstructure exhibits brittle tearing caused by the transformation of a large number of cavities derived from grain boundaries into adiabatic shear, accompanied by the production of dendritic crystals within the crystal.

       

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