Issues with contact and friction in thin-film devices are inevitable in the field of micro-engineering, especially in micro-electro-mechanical systems (MEMS). In this study, the nano-indentation and nano-scratching behaviours of pure nickel and NiTi shape memory alloy (SMA) nano-films, two common materials used in MEMS, were comparatively investigated using large-scale molecular dynamics simulations. For the nickel nano-film structure, the load–displacement (P–h) curve demonstrated distinct elasto-plastic characteristics, and visible permanent deformation remained after unloading. In contrast, for the NiTi SMA, the P–h curve formed a hysteresis loop, and no evident deformation remained on the surface after unloading. It is noteworthy that during scratching, despite a lower applied normal pressure on the nickel nano-film than on the NiTi SMA, the friction and friction coefficient of the former were much higher. These differences in performance are closely related to the super-elasticity induced by the martensitic transformation within the NiTi SMA.

薄膜器件中的接触和摩擦问题在微工程领域是不可避免的，尤其是在微机电系统 (MEMS) 中。在这项研究中，使用大规模分子动力学模拟比较研究了纯镍和 NiTi 形状记忆合金 (SMA) 纳米膜（MEMS 中使用的两种常见材料）的纳米压痕和纳米划痕行为。对于镍纳米膜结构，载荷-位移（P-h）曲线表现出明显的弹塑性特性，卸载后仍然存在可见的永久变形。相比之下，对于 NiTi SMA，P – h曲线形成滞后回线，卸载后表面无明显变形。值得注意的是，在划痕过程中，尽管对镍纳米膜施加的法向压力低于 NiTi SMA，但前者的摩擦和摩擦系数要高得多。这些性能差异与 NiTi SMA 内马氏体相变引起的超弹性密切相关。