Interactive contraction nanotwins-stacking faults strengthening mechanism of Mg alloys

Abstract Light-weight Mg alloys with higher strength are especially desirable for the applications in transportation, aerospace, electronic components and implants owing to their high stiffness, abundant raw materials and environmental friendliness. Nevertheless, the majority of traditional strengthening approaches involving grain refining and precipitation strengthening could effectively prohibit dislocation movement as well as compromise ductility invariably. Here we report a novel strategy for simultaneously achieving a high specific yield strength (182 ± 8 kNmKg−1) and a good elongation (21 ± 2%) in the Mg-13 wt% Li at room temperature, based on the formation of a hierarchical contraction nanotwins-stacking faults (CTWSFs) structure by cryorolling followed by ultrahigh pressure. Both of them are the highest values reported so far, even compared to commercial Al/Ti alloys and steel. The formation process and strengthening mechanism have been clarified by ex-situ transmission electron microscopy observation and molecule dynamics simulations. It demonstrates that this unique nanoscale interactive coherent interface structure is effective to prohibit dislocation motion in Mg crystal, analogous to twin boundaries. Those new results provide insights towards designing alternative and more innovative HCP-type structural materials with higher mechanical properties.