Spalling damage is one of the typical forms of material dynamic failure, of which the damage modes and physical mechanisms are directly related to the design of material impact protection. NiTi alloys have already been used in some dynamic extreme environments. However, its dynamic failure behavior and mechanism under high pressure and high strain rate are still unclear. In this study, nonequilibrium molecular dynamics simulations (NEMD) were used to explore the spalling modes and physical mechanisms of shocked nanocrystalline NiTi (nc-NiTi) at different loadings and temperatures. The results show that its spalling modes include classical-spall without melting state, multi-spall with partial-melting or partial-disorder states and micro-spall with complete melting or disorder states according to the thermodynamic states and melting characteristics of the spall region. It was found that the multi-spall or micro-spall depends on the homogeneity of the main Voronoi polyhedrons (VPs) of the short-range order (SRO) under different shock stresses, and that the spall strength at T${}_{\mathrm{0}}$=1000 K decreases more regularly than that of T${}_{\mathrm{0}}$=300 K with the increase of shock loading velocity Up. Moreover, increasing the initial ambient temperature T${}_{\mathrm{0}}$ from 300 K to 1000 K not only reduced the spall strength of nc-NiTi, but also reduced the critical stress required for different spalling modes. This is attributed to the temperature softening effect occupying a dominant position during the spalling, including the grain boundary diffusion and the change of the thermodynamic paths due to the increase of initial ambient temperature T${}_{\mathrm{0}}$.

剥落损伤是材料动态失效的典型形式之一，其损伤模式和物理机制直接关系到材料冲击防护的设计。NiTi合金已经在一些动态的极端环境中使用。然而，其在高压和高应变率下的动态破坏行为和机制尚不清楚。在这项研究中，非平衡分子动力学模拟 (NEMD) 用于探索在不同负载和温度下冲击纳米晶 NiTi (nc-NiTi) 的剥落模式和物理机制。结果表明，其剥落模式包括经典剥落无熔融态，根据剥落区域的热力学状态和熔化特性，分为部分熔化或部分无序状态的多层剥落和完全熔化或无序状态的微剥落。发现多剥落或微剥落取决于短程有序 (SRO) 的主要 Voronoi 多面体 (VP) 在不同冲击应力下的均匀性，以及 T 处的剥落强度${}_{\mathrm{0}}$=1000 K 比 T 更规律地减少${}_{\mathrm{0}}$=300 K 随着冲击加载速度 Up 的增加。此外，增加初始环境温度 T${}_{\mathrm{0}}$从 300 K 到 1000 K 不仅降低了 nc-NiTi 的剥落强度，而且还降低了不同剥落模式所需的临界应力。这归因于在剥落过程中温度软化效应占据主导地位，包括晶界扩散和由​​于初始环境温度 T 增加引起的热力学路径的变化${}_{\mathrm{0}}$.