Atomistic simulations of interaction between basal dislocations and three-dimensional twins in magnesium

• Published in: Acta materialia Vol. 155; no. C; pp. 187 - 198
• Main Authors: Gong, Mingyu, Liu, Guisen, Wang, Jian, Capolungo, Laurent, Tomé, Carlos N.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Ltd 15.08.2018; Elsevier
• Subjects: 3D twin; Atomistic simulation; Dislocation; Slip transformation; Atomistic simulation; Slip transformation; 3D twin; Dislocation
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2018.05.066

Dislocation slip and twinning are equally important in the plastic deformation of hexagonal close packed crystals. Basal slip and extension 101¯2<1¯011> twins can be activated concurrently in magnesium and, as a result, complex dislocation-dislocation, twin-twin, and dislocation-twin interactions take place and determine the hardening behavior. Here, using atomistic simulations, we study the latter mechanism, namely, the interactions between basal dislocations and a three-dimensional (3D) {101¯2} twin. According to our findings, a basal screw dislocation can fully transform into the twin via multiple cross-slip between basal and prismatic planes in the matrix. This process causes the formation of jogs and basal stacking faults in the matrix, and prismatic dislocations in the twin. We also find that a basal mixed dislocation cannot directly transform into the twin. Instead, it dissociates into twinning dislocations, resulting in a change in twin thickness and the formation of basal/prismatic steps. When the dislocation interacts with the lateral twin boundary, slip transformation in the twin is accomplished through the gliding of either ½<a+c> or <a+c> on the prismatic plane in the twin. Accompanying the gliding of ½<a+c>, a prismatic stacking fault is created inside the twin. By accounting for the 3D character of the dislocation-twin reactions, our results extend our understanding of slip transformation into a twin, the formation of basal and prismatic stacking faults in matrix and twin, and the role that local stresses and the lateral boundary of the twin play in this process. [Display omitted]