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).
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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