Strength and ductility with {10(1)over-bar1} - {10(1)over-bar2} double twinning in a magnesium alloy

Based on their high specific strength and stiffness, magnesium alloys are attractive for lightweight applications in aerospace and transportation, where weight saving is crucial for the reduction of carbon dioxide emissions. Unfortunately, the ductility of magnesium alloys is usually limited. It is thought that one reason for the lack of ductility is that the development of {10 (1) over bar1}-{10 (1) over bar2} double twins (DTW) cause premature failure of magnesium alloys. Here we show with a magnesium alloy containing 4 wt% lithium, that the same impressively large compression failure strains can be achieved with DTWs as without. The DTWs form stably across the microstructure and continuously throughout straining, forming three-dimensional intra-granular networks, a potential strengthening mechanism. We rationalize that relatively easier <c+a> slip characteristic of this alloy plastically relaxed the localized stress concentrations that DTWs can generate. This result may provide key insight and an alternative perspective towards designing formable and strong magnesium alloys.