Interaction of a moving { } twin boundary with perfect dislocations and loops in a hcp metal

Abstract

. Interaction of a moving 101-2 twin boundary with perfect dislocations and loops in an HCP metal. Philosophical Magazine, Taylor & Francis, 2010, 90 (07-08) AbstractAtomic-scale computer simulation is used to investigate the interaction of a moving twin boundary in an HCP metal with either a straight 1/3 dislocation lying perpendicular to the direction of twinning shear or a periodic row of perfect dislocation loops. The screw dislocation does not decompose in the moving interface and has no effect on its motion. The 60° mixed dislocation is attracted by the boundary and decomposes into twinning dislocations and a disconnection (an interfacial defect with both step and dislocation character): the sign of the crystal dislocation determines the form of the disconnection and thus its effect on twin boundary motion.Boundary reactions with crystal dislocations are likely to be important for assisting the twinning process. Loops with Burgers vector, b, parallel to the interface are reformed in the other crystal after the twin boundary has passed through. The boundary attracts both interstitial and vacancy dislocation loops with inclined b but is not transparent to them, for the complete loop is swept along its glide prism by the moving interface.Depending on its nature, a loop either retains its structure in its parent crystal or is absorbed in the interface. The decomposition product in the latter case is consistent with the reactions of straight dislocations. The results indicate that twinning is efficient at sweeping loops from the microstructure when their density is low and is suppressed by loops when their density is high.

Effect of the loading mode on the evolution of the deformation mechanisms in randomly textured magnesium polycrystals – Comparison of experimental and modeling results

“…Naturally, the interaction between twins and dislocations should also be taken into account. First of all, the twin boundaries can act as barriers for gliding dislocations (Serra and Bacon, 2010). Furthermore, the matrix dislocations can transmute upon the passage of a twin front and cause latent hardening in the twin, as it was suggested recently by Niewczas and El Kadiri & Oppedal (Niewczas, 2007;El Kadiri and Oppedal, 2010;Oppedal et al, 2012a).…”

Dynamic observation of dislocation evolution and interaction with twin boundaries in silicon crystal growth using in – situ synchrotron X-ray diffraction imaging

“…Likely, when the dislocation impinges in the boundary, it is shredded by atomic redistribution and then absorbed by the twin which acts as a sink. This may lead to the distortion at the core of the dislocation, as well as the formation of disconnections namely interfacial steps at the twin boundary [43]. Sangid et al [42] performed molecular dynamics simulations to study the dislocationtwin boundary interaction mechanisms.…”

Interface structures and twinning mechanisms of twins in hexagonal metals

“…PB or BP facets that bond basal and prismatic planes (the first character, B or P, represents the twin plane and the second character represents the matrix plane) on a TB represent a pair of disclination dipoles with associated strain fields that can be large [8,19]. More subtly, domain defects at corners of boundaries often have some dislocation character and associated strains [8,[52][53][54]. In particular, this is true for coherent twins at or near the critical size for twin nucleation [32].…”