Formation of {1 1 (2)over-bar 1} twins from I1-type stacking faults in Mg: A molecular dynamics study

The nature of the reaction and transient behavior of I-1-type stacking faults (SFs) under shear stress was investigated to understand the role of I-1 SFs in non-basal plastic deformation of Mg. This was because it has been suggested that I-1 SFs formed via solute (such as Y) additions to Mg may act as the nucleation source of non-basal dislocations, which serve as important deformation modes to improve the workability. Crystal models of pure Mg containing an I-1 SF were deformed by simple shear along the basal plane using molecular dynamics simulations with many-body interatomic potentials. The characteristic dissociation reaction was observed at the boundaries of the I-1 SF, where < c + a > dislocations on the pyramidal plane, Shockley partial dislocations on the basal plane, and stair-rod dislocations were nucleated. Interestingly, instead of activation of the non-basal dislocations, {11 (2) over tilde1} twins were nucleated in the early stage of the reaction and grew steadily as the applied stress was increased. It was suggested that the I-1 SF was likely to act as a reactive defect to assist and accommodate the c-axis deformation. Further, the deformation-induced twin boundaries were found to act as moderate obstacles to dislocation movement on the basal planes in the Mg matrix, without significantly sacrificing its plasticity. (C) 2016 Elsevier B.V. All rights reserved.