Study on the Tribological Behavior and Mechanism of Cu-Mg Alloy under Coupled Elevated Temperature and Pre-corrosion Conditions

Cu-Mg alloy droppers in high-speed railways operate under complex conditions involving corrosion, heat, and mechanical load. However, the synergistic damage evolution mechanisms under such multi-physics coupling remain unclear. This study investigated the tribological behavior of CuMg0.4 alloy using a crossed-cylinder configuration, focusing on the synergistic effects of normal load, pre-corrosion, and temperature. The results indicate that the higher loads are associated with the formation of a more compact mechanically mixed layer (MML), which corresponds to more stable friction and a lower wear depth. In contrast, pre-corrosion severely deteriorates frictional stability due to brittle layer fragmentation and subsequent three-body abrasion. Notably, temperature exerted opposite effects on uncorroded and corroded surfaces. For uncorroded substrates, elevated temperatures (90–120 °C) increase wear depth via thermally activated plastic flow. Nevertheless, for pre-corroded specimens, the elevated temperature promotes a more pronounced tendency for surface reconstruction. The reduced post-wear Cu enrichment, together with the continued detection of O/Cl-containing species on the wear scar, suggests that the fractured corrosion products and wear debris are more readily retained and compacted within the contact zone at the elevated temperature. As a result, the worn surface tends to develop a more continuous and compact tribolayer consistent with MML formation, which is associated with reduced substrate exposure and lower material loss. The surface reconstruction tendency identified in this study provides further insight into the damage evolution of copper alloys under multi-physics coupling.