Strengthening Mechanism of Cold-Sprayed Al6061 Protective Coating on LAZ931 Mg-Li Alloy

To address the key problems of dual-phase magnesium-lithium alloy LAZ931 such as easy corrosion, flammability and low strength, AA6061 protective coating was fabricated on LAZ931 alloy via cold spraying to form an Al6061/LAZ931/Al6061 sandwich structure. The strengthening mechanism of the coating on interfacial microstructure, mechanical properties, creep behavior and corrosion resistance was systematically investigated. The results show that the cold-sprayed AA6061 coating is compact and uniform with a low porosity of 0.3% and surface roughness of 37.02 μm, which significantly improves the combustion resistance and corrosion resistance of the alloy. The coating/substrate interface exhibits jagged and tight bonding without obvious cracks or delamination. Abundant dislocations and Al–Mg–Li composite precipitates form at the interface, which effectively strengthen the interfacial bonding and enhance the tensile and yield strengths. Room-temperature creep tests reveal that the creep behavior of the composite is dominated by the LAZ931 matrix, and the coating carries load synergistically to improve deformation stability. Electrochemical impedance spectroscopy shows that the coating increases the low-frequency impedance by more than two orders of magnitude, greatly elevating corrosion resistance. This study confirms that cold-sprayed AA6061 protective layer can comprehensively enhance LAZ931 alloy through interfacial bonding, microstructural strengthening and protective barrier effects, providing a new strategy for protection and toughening of ultra-light Mg-Li alloys.