Interactions between 〈a〉 dislocations and three-dimensional [formula omitted] twin in Ti

Abstract

〈a〉dislocations on basal or prismatic planes and {112¯2} compression twins are commonly activated in deformed Titanium (Ti). In the present work, their interactions are investigated by both crystallographic analysis and atomistic simulations. For a three-dimensional {112¯2} twin, we firstly analyze seven possible twin boundaries (TBs) bonding two low index planes in matrix and twin. Next, we focus on the two lower energy boundaries, {112¯2}M/T∥{112¯2}T/M coherent twin boundary (CTB) and {1¯21¯1}M/T∥{12¯11¯}T/M. Depending on dislocation character and boundary type, we define four types of interactions between 〈a〉 dislocations and these TBs. Further, we predict possible dislocation reactions on/across TBs using crystallographic analysis according to the deformation compatibility and the change in elastic energy, such as twinning/detwinning of the primary twin, slip transmission and secondary twinning, for each type of interaction. Molecular dynamics (MD) simulations are then conducted for all interactions under pre-selected loadings in order to explore the dynamic process associated with each of these interactions and examine the predicted reactions. MD simulations predict that the interaction between 〈a〉 dislocations and some facets can lead to the formation of secondary twins and 〈a〉 dislocations on basal or prismatic planes in twins, and reveal the possibility of forming 〈c〉 and 〈c+a〉 dislocations in twins. Moreover, some of the possible reactions take place on lateral TBs other than CTBs.