Europhys. Lett.
Volume 68, Number 3, November 2004
Page(s) 405 - 411
Section Condensed matter: structure, mechanical and thermal properties
Published online 16 October 2004
Europhys. Lett., 68 (3), pp. 405-411 (2004)
DOI: 10.1209/epl/i2004-10201-y

Twinning pathway in BCC molybdenum

S. 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 $(2\bar{1}\bar{1})\langle111\rangle$ twinning energy landscape of BCC $\chem{Mo}$ 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 $\un{mJ/m^2}$ and 40 $\un{mJ/m^2}$, 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 $\un{GPa}$; 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