Deformation criterion for face-centered-cubic metal nanowires

Much of our understanding of the tendency for deformation by dislocation slip (DS) versus deformation twinning (DT) in bulk metals relies on the magnitude of the stacking fault energy (SFE). However, the criterion based only on SFE is insufficient for evaluating the deformation behavior of nanowires (NWs) and possibly nano-grained crystalline metals. Here, by employing fault energy theories and dislocation theory, we have developed a parameter that enables the quantitative analysis of the relative tendency for DS and DT in Al NWs. In situ TEM tensile tests and atomic simulations of Al NWs showed that the competition between DS and DT is sensitive to the misfit energy, crystal size, and loading direction. Additional studies were conducted on Au and Pt NWs to determine the applicability of the proposed theory to other crystals. The theory produces self-consistent results even for metals with different SFE values.