Influence of Nano-Lubricants on Edge Cracking and Surface Quality of Rolled Mg/Al Composite Foils

This study systematically investigates the effect and mechanism of a TiO₂ nano-lubricant on edge cracking and surface quality during the rolling of Mg/Al composite foils. Initial friction and wear tests identified an optimal nano-lubricant concentration of 3.0 wt.%, at which the system achieved a minimum average coefficient of friction of 0.067. Subsequent rolling tests using this concentration showed that the nano-lubricant reduced rolling force by 5.39–7.54% compared to dry conditions. It also significantly suppressed the initiation and propagation of edge cracks. Furthermore, the surface roughness parameters Ra and Rz were reduced by 16.5% to 24.0%, and the height profile fluctuation range was reduced by 33% to 45%, resulting in a smoother and more uniform surface morphology. The analysis of the underlying mechanism indicates that the superior performance originates from the synergistic effects of the rolling effect, the mending effect, the polishing effect, and the protective film effect. This work establishes that the use of a 3.0 wt.% TiO₂ nano-lubricant is a viable strategy for fabricating high-quality Mg/Al composite foils with minimal defects. It thereby offers both theoretical and practical guidance for the advanced rolling of bimetallic composites.