Anomalous temperature dependence of shock response in a refractory multi-principal element alloy: from shear localization to homogeneous plasticity

Abstract The shock response and underlying deformation mechanisms of a polycrystalline MoNbTa refractory multi-principal element alloy (RMPEA) are investigated using large-scale molecular dynamics simulations. The simulations systematically explore the effects of initial temperature on the dynamic mechanical response and microstructural evolution. The results revealed that within the initial temperature range of 5–1200 K, the shock behavior of MoNbTa RMPEA exhibited a weak temperature dependence. The longitudinal and transverse stresses only slightly decrease with the increase of temperature, while the waveform changes of stress, particle velocity and density remain almost unchanged, demonstrating the high-temperature impact stability. The analysis of the stress state indicates that volumetric strain and distortion strain are separated. Hydrostatic pressure maintains a continuous and stably propagating impact front, while von Mises stress maps the persistent non-uniform plastic zone behind the front, indicating that energy is widely dissipated through defect-induced plasticity. In addition, the shock damage is mainly manifested in the diffusion of the initial grain boundary dislocation network, the formation of dislocations within the grains, and amorphous transformation. Some damaged structures can recover dynamically after the shock. Compared with pure Nb and NbMo alloys, MoNbTa RMPEA exhibits suppressed amorphization, reduced grain boundary degradation, and superior resistance to catastrophic shear localization under extreme shock loading. These findings provide atomic‐scale insight into the coupled effects of temperature and high‐strain‐rate deformation in RMPEAs.