Coherent interface strengthening of ultrahigh pressure heat-treated Mg-Li-Y alloys

Achieving good strength-ductility of Mg alloys has always been a crucial issue for the widespread applications of Mg-based structural materials.Herein,an unexpected double-stage strengthening phenomenon was discovered in Mg-8Li-1Y(wt.%)alloys through high pressure(6 GPa)heat treatments over a range of 700-1300℃.Attractively,the yield strength values are improved remarkably without losing their ductility.The low temperature strengthening mechanism is mainly driven by the formation of large-volume nanoscale contraction twins.In contrast,the high-temperature strengthening reason is ascribed to the presence of densely nano-sized stacking faults.Both coherent interfaces contribute effectively to high mechanical strength without any tradeoff in ductility.