Mechanism for the Formation of Partial Stacking Faults in Magnesium

Anomalous basal stacking faults (SFs) have been frequently observed inside {10-11} and {10-12} twins in hexagonal close-packed metals. These SFs were first described by Song and Gray as "partial stacking faults" in the sense that only every other basal plane is displaced by the SFs. To further understand the formation mechanism of these SFs, in this work, we performed lattice correspondence analysis in the simulations of these two twinning modes. The corresponding plane of the parent to the prismatic plane of the twin was pre-selected and tracked before and after twinning. The atomic positions were closely examined to reveal the stacking sequence change in the twin due to the formation of the basal SFs. The results show that, indeed, only half of the atoms are displaced by the presence of the basal SFs, indicating that no global displacement vector can be defined and no dislocation activities are involved in the formation of the SFs. A special configuration of SFs was observed, which has limited mobility via coordinated atomic shuffles.