Towards resolving the anonymity of pyramidal slip in magnesium

Plasticity in magnesium crystals oriented for c-axis compression has been usually attributed to 〈c+a〉 dislocation slip on second-order pyramidal {112¯2} planes. Through molecular dynamics simulations, we investigated the formation and slip characteristics of 〈c+a〉 dislocations on second-order pyramidal planes. It is shown that the critical c-axis compressive stress for these dislocations is almost seven times that for 〈c+a〉 dislocations on first-order pyramidal {101¯1} planes. In particular, it is concluded that first-order pyramidal near-screw 〈c+a〉 dislocations play a predominant role during the c-axis compression of magnesium crystals. Careful reexaminations of published experimental observations show good agreements with the current predictions.