In this work, the dynamic behavior of nano-bubbles near the surface of single crystal iron (Fe) was investigated using molecular dynamics simulations. The cavitation erosion behavior of single crystal Fe and the structural evolution of its eroded surface was examined at different bubble diameters. The results show that nano-bubble diameter is inversely correlated with impact pressure and diameter is positively correlated with nanojet energy. The volume, surface area, and depth of cavitation pits are nearly directly proportional to the bubble diameter with correlation linear fitting coefficients of R2 = 0.9837, R2 = 0.9922, and R2 = 0.9799, respectively. Additionally, cavitation erosion induces the structural evolution of iron atoms from bcc to fcc and hcp structures. The percentage of new phase transformed is related to the bubble diameter and the type of transformed structure, the percentage of fcc and hcp structures of Fe atoms exhibits an increasing trend with the increase in the bubble diameter, and the Fe atoms of fcc structures occur an obvious increase beyond a bubble diameter of 12 nm.

Copper matrix self-lubricating composites are critical for high-temperature industrial applications. In this study, Cu-Ni-Sn-Mo-Gr composites with 3–7 wt.% graphite were fabricated via spark plasma sintering (SPS). The influence of graphite content on microstructure, mechanical properties, and tribological behavior from room temperature (RT) to 500 °C were systematically investigated. The results demonstrate that increasing graphite content progressively reduces density, hardness, and yield strength, whereas it significantly enhances high-temperature tribological performance. The composites with 7 wt.% graphite addition achieve outstanding self-lubricity and wear resistance across the RT-500 °C, achieving an average friction coefficient of 0.09 to 0.21 and a wear rate of 1.32 × 10⁻⁶ to 7.52 × 10⁻⁵ mm³/N·m. Crucially, temperature-dependent lubrication mechanisms govern performance: graphite-dominated films enable friction reduction at RT, while synergistic hybrid films of graphite and in situ-formed metal oxides (Cu₂O, CuO, NiO) sustain effective lubrication at 300–500 °C.