Underlying mechanisms for deformation and fracture behaviour of some BCC and FCC high entropy alloys

Abstract

In this investigation synergistic assessments of fracture toughness and activation volume for plastic deformation of two typical body centered crystalline (bcc) and face centered crystalline (fcc) high entropy alloys containing Al, Cr, Co, Cu, Fe and Ni have been made by standard practices; these experiments together with the assessment of conventional mechanical properties were carried out to understand the underlying mechanisms responsible for the deformation and fracture response of high entropy alloys. The estimations of the mechanical properties are supplemented by micro- and sub-structural examinations using optical, scanning and electron microscopy as well as X-ray diffraction analyses. The major results indicate that the bcc alloy exhibits higher hardness and strength with inferior fracture toughness compared to the fcc alloy. This characteristic observation has been explained with the nature of the constituent phases in the two alloys, the magnitudes of the activation volume which dictate the underlying deformation mechanisms and some limited qualitative signatures of the dislocation characteristics. The exploration and the understanding of the underlying mechanisms for deformation and fracture would assist the technologists to evaluate the potential of high entropy alloys for structural applications.