Experimental and numerical study on the dynamic shear banding mechanism of HfNbZrTi high entropy alloy

High-entropy alloys (HEAs) have attracted considerable attention in recent years because of their unique mechanical properties. In this work, the mechanism of dynamic shear banding (also called adiabatic shear bands, ASBs) in a BCC HEA HfNbZrTi was investigated combining dynamic experiments and numerical simulations. The temperature evolution during dynamic shear banding, which has been believed to play a dominant role during ASB formation in the literature, was measured using high-speed infrared thermal detectors synchronized with a split Hopkinson pressure bar system. The dynamic mechanical behavior of the BCC HEA was described using the Johnson-Cook model accompanied by damage accumulation. The process of ASB formation, considering potential contributions from thermal softening and damage softening, was numerically investigated by controlling the activation of each softening mechanism separately. Based on the results of experimental observation and numerical analysis, dynamic shear banding in this BCC HEA is proposed to be dominated by damage softening, and thermal softening only plays a secondary role, which differs from the thermal-softening-dominated ASB formation in typical FCC HEAs such as the Cantor alloy.