Effect of Precipitation Strengthening on Dynamic Mechanical Properties of CoCrFeNiTi_0.2 Multiphase High Entropy Alloy

CoCrFeNiTi_0.2 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.