Microstructure and mechanical properties of ultra-lightweight Mg-Li-Al/Al-Li composite produced by accumulative roll bonding at ambient temperature

Microstructural evolution and mechanical properties of ultra-lightweight Mg-14 wt% Li-1wt.% Al/Al-2wt.% Li composite produced by accumulative roll bonding (ARB) at ambient temperature were investigated. The computational simulation revealed the complicated stress and strain distribution in Mg-Li-Al and Al-Li layers during ARB process. The compositions of Al and Mg elements across the interface between Mg-Li-Al and Al-Li layers were increasingly homogeneous with the increase of ARB cycles due to the atomic inter-diffusion, indicating that the bonding between Mg-Li-Al and Al-Li layers was gradually improved. The grain sizes of Mg-Li-Al and Al-Li layers were decreased to about 300 nm and 200 nm after 4 cycles of ARB process, respectively. The brittle intermetallic compounds of Al3Mg2 and Al12Mg17 were gradually formed with the increase of ARB cycles. The microhardness and strength of Mg-Li-Al/Al-Li composite continuously increased, however, the ductility first decreased and then increased with the increase of ARB cycles. The tensile properties, with the ultimate tensile strength (UTS) of 308 MPa and the elongation (EL) of 17.4%, were achieved after 4-cycle ARB process.