Dynamic testing at high strain rates of an ultrafine-grained magnesium alloy processed by ECAP

A ZK60 magnesium alloy was processed by equal-channel angular pressing (ECAP) at 473 K to produce a grain size of similar to 0.8 mu m and it was then tested under dynamic conditions at strain rates up to 4.0 x 10(3) s(-1) using a split-Hopkinson bar. The stress-strain curves in dynamic testing exhibited upwards concave curvature suggesting the occurrence of twinning. Examination by transmission electron microscopy showed that dislocation slip played a major role in the flow behavior with dislocation accumulation as the main source of work hardening. An identification of Burgers vectors revealed the extensive presence of prismatic dislocations. Rod-shaped Mg-1 (Zn,Zr)(1) precipitates present in the as-received alloy become fragmented and overaged during ECAP. (C) 2009 Elsevier B.V. All rights reserved,