Atomic-Scale Comparison Between {(1)over-bar101} and {(1)over-bar102} Twin Growth Mechanisms in Magnesium

The two most frequently observed twins in hexagonal close-packed (HCP) Mg, {(1) over bar 101} and {(1) over bar 102} twins, have surprisingly different properties and morphologies, with {(1) over bar 101} twins appearing under higher stresses and being much thinner than {(1) over bar 102} twins. By considering the atomic-scale elementary properties of the twin interfaces and their disconnections, we show that (1) the transverse propagation of {(1) over bar 101} twins is hindered by the absence of low-energy mobile interfaces, whereas {(1) over bar 102} twins benefit from prismatic-basal interfaces and (2) the thickening of {(1) over bar 101} twins is slowed by higher energy barriers against both the nucleation and propagation of disconnections along their interfaces.