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Strengthening and toughening by partial slip in nanotwinned diamond

Yang, Bo, Peng, Xianghe, Huang, Cheng, Wang, Zhongchang, Yin, Deqiang, Fu, Tao
Carbon 2019 v.150 pp. 1-7
carbon, deformation, hardness, silicon
It was reported recently that synthesized nanotwinned diamond (nt-diamond) possesses unprecedented hardness and ductility, however, the role of nanotwins in strengthening and toughening mechanisms remains unclear. In this article, we compared the atomic reconfiguration patterns of nt-diamond and nt-Si obtained with first principles calculations. We found that the detwinning in nt-diamond, which can be achieved by partial slip on the glide-set plane, could account for the strengthening of nt-diamond. Such continuous partial slip could lead to an extremely large increase in strain range and intragranular deformation resistance for nt-diamond. In contrast, the stress of nt-Si could be released by the slip on the shuffle-set plane, which could not induce detwinning. Different responses in nt-diamond and nt-Si can be accounted for with their generalized stacking fault energies (GSFEs). The glide-set plane in diamond has lower GFSE, therefore, the atoms would slide preferentially along the glide-set plane; while in Si, the shuffle-set plane has lower GFSE. These results can provide insights into the atomic reconfiguration as well as the unprecedented strength and ductility of nt-diamond under shear deformation.