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 < 01 (1) over bar0 > 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.