Twinnability of hcp metals at the nanoscale
YF Guo and S Xu and XZ Tang and YS Wang and S Yip, JOURNAL OF APPLIED PHYSICS, 115, 224902 (2014).
Twinning is generally considered to be the primary deformation mechanism for hexagonal close-packed (hcp) metals due to their limited slip systems. Recent microcompression experiments point to strong size effects indicating that pyramidal slips can dominate in deformation under compression. We present analysis on the twinnability of an ideal hcp single crystal at the nanoscale. A criterion for deformation twinning is derived by considering the elastic lattice-rotation strain, and the result tested against molecular dynamics simulations of magnesium and titanium single crystals. We find < c + a > pyramidal slip dominates the compression deformation at the nanoscale, which is consistent with experimental observations on microcompression. This analysis gives an interpretation of size effects in deformation twinning, at the same time it provides an explanation for the so-called strength differential effect. (C) 2014 AIP Publishing LLC.
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