Removing basal-dissociated < c plus a > dislocations by 10(1)over-bar2 deformation twinning in magnesium alloys

XZ Zhou and HH Su and HQ Ye and ZQ Yang, ACTA MATERIALIA, 217, 117170 (2021).

DOI: 10.1016/j.actamat.2021.117170

Reactions of 10 (1) over bar2 twin boundaries (TBs) with dislocations in a Mg alloy subjected to cyclic deformation were studied and modeled, based on atomic-resolution observations, theory of interfacial defects and molecular dynamics (MD) simulations. Atomic-resolution observations provide evidence for occurrence of reactions of 10 (1) over bar2 TBs with basal < a(60)> and basal-dissociated < c + a > dislocations upon back and forth migration of 10 (1) over bar2 TBs, respectively, during cyclic deformation. MD simulations show that immobile basal-dissociated < c + a(s)>,< c + a(60)> and < c > dislocations in Mg can be incorporated into 10 (1) over bar2 TBs to produce steps which can move together with the TBs upon twinning/detwinning under low shear stresses. And such steps can usually emit < a(60)> dislocations under simultaneous application of shear and normal stresses. Importantly, the normal stresses required to transmute immobile basal-dissociated < c + a > dislocations to glissile < a(60)> dislocations are much lower than those required to transmute basal < a(60)> dislocations to < c + a > dislocations during 10 (1) over bar2 deformation twinning. Our results may have implications for comprehensive understanding of the roles of deformation twinning, < c + a > dislocations, and their interactions/reactions in plastic deformation of Mg alloys. (C) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

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