Deformation twinning of ultrahigh strength aluminum nanowire

Recent studies have demonstrated that many metal nanowires (NWs) with low stacking-fault energies display ultrahigh strength and can accommodate large plastic strains by spreading mechanical twins throughout the entire volume of the NWs. This previous observation on the plasticity, however, is largely different from that exhibited by Al NWs. In situ tensile tests performed on the <110> Al NW revealed that the NW exhibited ultrahigh strength (∼2.7 GPa) and superelasticity (∼4.8%), while contrary to expectations, it failed quickly once plastic flow initiates and displayed a limited plasticity (∼1.2%). This low plasticity was attributed to the formation of thin-layered twins with a zigzag configuration. Upon further deformation, these twins self-locked with each other, which prevented the NWs from carrying further plastic strains. Here, by employing the in situ micro-mechanical test and the atomic simulations, we performed quantitative and comprehensive analyses to explore why Al NWs display ultrahigh strength and how twins with a zigzag configuration are formed in the Al NWs.