Deformation due to migration of faceted {101¯2} twin boundaries in magnesium and cobalt

Abstract

Recent experimental observations show that $\{10\overline{1}2\}$ twin boundaries in hexagonal close-packed (hcp) metals are frequently faceted. The objective of this paper is to investigate the influence of this faceting on the strain produced by twinning. We show that basal–prismatic (BP) facets are terminated by opposite disclinations and the migration of these facets along a straight $\{10\overline{1}2\}$ twin boundary produces ordinary twinning shear. On the other hand, joining conjugate twins gives rise to BP facets terminated on the parent twin boundaries by identical disclinations. In this case, the strain produced by the migration of BP facets is an average between the strains produced by the individual conjugate twins. These theoretical studies are complemented by two EBSD measurements on cobalt that is closely related to magnesium. The misorientation profiles measured across two conjugate twin boundaries yield a misfit of approx. 7° consistent with the theoretical prediction that the corner of a twin embryo is terminated by two identical disclinations, each accommodating a misfit of 3.7°.

Keywords:

• twinning
• computer simulation
• faceting
• deformation
• grain boundaries

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Academy of Sciences of the Czech Republic, project No. RVO:68081723. This work has been carried out at the Central European Institute of Technology (CEITEC) with research infrastructure supported by project CZ.1.05/1.1.00/02.0068 financed from the EU Structural Funds.