Synergistic enhancement of corrosion resistance in LZ91 Mg-Li alloys via ultrasonic surface rolling process and micro-arc oxidation

Dual-phase Mg-Li alloys such as LZ91 offer exceptional lightweight properties and high specific strength, making them highly promising for aerospace and automotive applications, yet their widespread use is severely limited by poor corrosion resistance. To address this issue, a synergistic surface modification strategy combining ultrasonic surface rolling process (USRP) and micro-arc oxidation (MAO) is introduced for LZ91 Mg-Li alloy. Systematic investigations reveal that USRP pretreatment significantly enhances surface integrity by reducing roughness and introducing compressive residual stresses, while subsequent MAO forms a dense 15-μm-thick ceramic coating primarily composed of MgSiO₃ and MgO. The combined treatment improves coating adhesion by 20.3%, reduces porosity by 63.1%, and achieves further enhanced corrosion resistance compared with MAO-only samples. Microstructural analyses show that USRP-induced grain refinement and dislocation accumulation promote a uniform MAO layer with enhanced resistance to crack propagation and chloride penetration. This work demonstrates a scalable approach to enhancing the corrosion resistance of Mg-Li alloys, presenting a viable strategy for their application in aerospace and automotive industries.