Dislocation configurations in an extruded ZK60 magnesium alloy

Transmission electron microscopy (TEM) was performed to study the types of dislocations and their configurations in a commercially extruded ZK60 magnesium (Mg) alloy. We mainly employed the weak-beam dark-field (WBDF) technique with 〈0110〉 zone axis to unambiguously identify Burgers vectors of various types of dislocations in the microstructure. It was found that nonbasal 〈a〉 dislocations and 〈c〉 dislocations were predominant. No 〈c+a〉 was observed. Rearrangement of these dislocations, due to dynamic recovery during extrusion, led to cell walls and low-angle grain boundaries with relatively high density dislocations. Dissociation of the 〈c〉 dislocations with a relatively narrow split distance was observed. The dissociated 〈c〉 dislocations could form a nodular structure. Fringes of stacking faults from the dislocation dissociation were observed.