Twinning pathway in BCC molybdenumS. Ogata1, 2, 3, J. Li4 and S. Yip1, 5
1 Department of Nuclear Engineering, Massachusetts Institute of Technology Cambridge, MA 02139, USA
2 Handai Frontier Research Center, Osaka University - Osaka, Japan
3 Department of Mechanical Engineering and Systems, Osaka University Osaka 565-0871, Japan
4 Department of Materials Science and Engineering, Ohio State University Columbus, OH 43210, USA
5 Department of Materials Science and Engineering Massachusetts Institute of Technology - Cambridge, MA 02139, USA
received 27 May 2004; accepted in final form 27 August 2004
published online 16 October 2004
The twinning energy landscape of BCC is determined using the density functional theory for embryos containing 2 to 7 layers. The 2-layer embryo is metastable, whereas the 3- and 4-layer ones are unstable. Layer-by-layer growth starts at 5 layers. The twin boundary formation and migration energies are found to be 607 and 40 , respectively, indicating that twin partial dislocations have wide cores and high mobilities. The stress to homogeneously nucleate an additional partial loop on the boundary of a sufficiently thick twin is only 1.4 ; this implies that once a deformation twin reaches critical thickness, which we estimate to be 6 layers, subsequent growth in thickness is easy.
62.20.Fe - Deformation and plasticity (including yield, ductility, and superplasticity).
61.72.Nn - Stacking faults and other planar or extended defects.
61.72.Mm - Grain and twin boundaries.
© EDP Sciences 2004