Temperature-dependent variation in dynamic deformation behaviour and dislocation substructure in AZ80 magnesium

摘要

The dynamic deformation behaviour and dislocation substructure of AZ80 magnesium alloy are investigated at strain rates of 8 x 10(2), 1.5 x 10(3) and 2.2 x 10(3) s(-1) and temperatures of - 100, 25 and 300 degrees C using a compressive split-Hopkinson pressure bar system. The flow stress, work hardening coefficient, strain rate sensitivity and temperature sensitivity all increase with increasing strain rate or decreasing temperature. Moreover, the dynamic deformation behaviour is well described by the Zerilli-Armstrong hexagonal close packed (hcp) constitutive equation. Catastrophic failure occurs at all three temperatures under strain rates of 1.5 x 10(3) and 2.2 x 10(3) s(-1). Transmission electron microscopy observations show that the dislocation density increases with a higher strain rate or a lower temperature. Finally, the flow stress varies linearly with the square root of the dislocation density in accordance with the Bailey-Hirsch model.