Investigation of thermal and mechanical effects during electrically-assisted compression of CoCrFeNiW0.5 high entropy alloy

Abstract

Electrically-assisted manufacturing (EAM) has many advantages than ambient temperature manufacturing and thermoforming for the building of hard-to-deform alloys. The EAM technique of High entropy alloys (HEAs), a newer alloy category, is an issue worth of research, especially the deformation mechanism in the process of EAM. In the paper, the electrically-assisted compressive mechanical behavior of CoCrFeNiW0.5 HEA composed of face centered cubic phase and μ phase precipitate was studied under current density and strain rate region of 0–40 A/mm2 and 0.0005 s−1-0.1 s−1, respectively. At high current density and strain rate, the reduction of yield stress is remarkable. Electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) techniques were utilized to analyze the effect of current density on the flow stress behaviors and microstructure evolution under plastic deformation. The results show that the introduced electric current enhances the movement and annihilation of dislocations as well as dynamic recovery, resulting in the continuous decrease of flow stress. Additionally, we can clearly observed that the dislocation-free ring or some very low dislocation density regions around the μ phase precipitates, that's because μ phase precipitate can lead to severe lattice distortion and thus increase the electron scattering, and then the local high temperature appeared around the defect regions due to local Joule heating effect, which is recognized as the principal reason leading to the significant decrease of mechanical properties during electrically-assisted compression.