Accommodation and formation of {1¯012} twins in Mg-Y alloys

The {1¯012} tensile twins terminating inside the grains of a deformed Mg-Y alloy were investigated by transmission electron microscopy. The crystallographic features of terminating twins and associated slip structures were quantified and correlated. The local stresses developed at a terminating {1¯012} twin were computed using crystal plasticity simulations in order to interpret the observed slip patterns. Results indicate that both basal 〈a〉 and 〈c+a〉 matrix glide were involved in accommodating the plastic stresses developed in the vicinity of terminating twins. Along the twin boundary, the defect contrast consistent with that of lattice dislocations and twinning partials was observed. Based on these observations, a dislocation reaction is proposed that establishes an interrelationship between the observed matrix glide and {1¯012} twinning in Mg-Y alloys.