Interactions between a migrating {101¯1} twin boundary and a 〈 c 〉 or 〈 c+a 〉 dislocation in magnesium

We conducted molecular dynamics simulations to study the interactions between a migrating {101¯1} twin boundary (TB) and prismatic 〈 c 〉 and 〈 c + a 〉 dislocations in magnesium. In the simulations, the 〈 c + a 〉 dislocation comprises 〈 c 〉 edge and 〈 a 〉 screw components. Both of these 〈 c 〉 and 〈 c + a 〉 dislocations are observed to exhibit a dissociated core comprising two partial dislocations. Upon interaction with a (101¯1) TB, these partials pin the TB and reside on a pyramidal-basal (PyB) or basal-pyramidal (BPy) twin interface. It was found that one of the two partials transmutes into a basal 〈 a 〉 dislocation inside the (101¯1) twin, and the other transforms into a Frank partial dislocation that is inside the twin and linked with a single-atomic-layer-height disconnection on the TB. The basal 〈 a 〉 dislocation has its extended core bounded by two Shockley partial dislocations. The simulations reveal that when the 90° Shockley is positioned close to the TB, the full 〈 a 〉 dislocation easily detaches. In contrast, when the 30° Shockley is located close to the TB, the 〈 a 〉 connects to the TB and migrate with the TB synchronously. It was observed that connection of the 〈 a 〉 to the (101¯1) TB leads to a configuration comprising an I₂ fault with one end linked to a two-atomic-layer-height disconnection on the TB through a 30° Shockley partial dislocation. Further examination suggested that such a two-atomic-layer-height disconnection has its riser plane parallel to a PyB interface when the shear direction of the connected I₂ points towards the TB, while has its riser plane parallel to a BPy interface when the shear direction of the connected I₂ points away from the TB.