Coupling effect of temperature and strain rate on mechanical properties and deformation mechanisms of Cr26Mn20Fe20Co20Ni14 high-entropy alloy

Abstract

It is proposed that high-entropy alloys (HEAs) with face-centered cubic (FCC) structure possess superior strength-ductility synergy at low temperature or high tensile rate, attributing to enhanced twinning ability. In present work, the coupling effects between low temperature and high strain rate on the mechanical properties and deformation mechanisms of the Cr26Mn20Fe20Co20Ni14 HEA were investigated. Compared with that at room temperature (RT) with a strain rate of 10−3 s−1, the HEA exhibits enhanced strength but sacrificial ductility at liquid nitrogen temperature (LNT) with a higher strain rate of 10−1 s−1. Investigation of the microstructures reveals that twinning and stacking fault dominate the deformation at RT with a strain rate of 10−3 s−1. At LNT and 10−1 s−1, the deformation is inhomogeneous, characterized by local twinning and dislocation planar slip as well as relatively less HCP phase transformation. Moreover, numerous cracks induced by weakened interfaces and high flow stress at LNT lead to premature fracture.