Abstract: This study investigates the mechanical properties and energy release behaviours of W_xNbTiZr medium entropy alloys under varying strain rates, ranging from 1 × 10^-3 s^-1 to 4 × 10³ s^-1. The results reveal significant strain rate sensitivity, with dynamic loading enhancing the strength of these alloys compared to quasi-static conditions. Notably, the alloys W_0.5NbTiZr and W_0.75NbTiZr exhibit reduced sensitivity due to their higher density of grain and phase boundaries, which impede dislocation movement. Single-phase alloys (with x ≤ 0.25) do not undergo fragmentation or energy release at any tested strain rates, while dual-phase alloys (W_0.5NbTiZr, W_0.75NbTiZr, and WNbTiZr) show severe fragmentation and combustion beyond specific strain rate thresholds. Theoretical calculations suggest that higher tungsten content should result in lower energy release, but experimental observations indicate that W_0.75NbTiZr releases the least energy, highlighting the importance of microstructure in addition to composition. The fragmentation process is associated with the formation of adiabatic shear bands and microcracks along the pearl chain microstructure, leading to multiple exothermic events. The WNbTiZr alloy, with its prevalent pearl chain structure, demonstrates the most comprehensive properties, emphasizing the significance of integrated alloy design strategies that optimize both composition and microstructure.

Key words: Energetic structural materials, Medium entropy alloy, Dynamic mechanical property