Effects of Shock Peak Stress and Pulse Duration on Spall Damage of NbTiZr Medium-Entropy Alloy

Dynamic mechanical behaviors of high entropy alloys (HEAs) or medium-entropy alloys (MEAs) have attracted significant attention due to their exceptional strength-toughness balance and promising potential applications in extreme conditions. This work investigates the effects of peak shock stress and pulse duration on the spall damage of the NbTiZr MEA under dynamic shock loading. Peak shock stresses, pulse durations and spall strengths are determined by analyzing free surface velocity profiles, with postmortem microstructural analysis to reveal the underlying deformation and failure mechanisms. The measured spall strength of NbTiZr MEA ranges from 3.77 GPa to 4.80 GPa, showing minimal dependence on the peak shock stress but high sensitivity to the pulse duration. Furthermore, the damage morphologies are significantly influenced by pulse durations. The damage is recognized as a quasi-cleavage fracture mode. No phase transition or deformation twins are observed within the recovered NbTiZr alloy.