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

Abstract

The dynamic deformation behaviour and dislocation substructure of AZ80 magnesium alloy are investigated at strain rates of 8 × 102, 1.5 × 103 and 2.2 × 103 s−1 and temperatures of −100, 25 and 300°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 × 103 and 2.2 × 103 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. This paper is part of a thematic issue on Light Alloys.

Light alloys

“…The inclusion of recent examples of simulations applied to Al and Mg alloys adds greatly to the value of the review. The original research articles that follow are then loosely grouped according to subject, commencing with studies on underpinning metallurgy [2][3][4][5], cast alloys [6][7][8], the properties and performance of extruded products [9][10][11][12], before moving to parallel tubular angular pressing [13] and selective laser melting [14]. The remaining articles deal with materials that may be considered to be composites based on an aluminium alloy, and these include an important contribution on foams [15], as well as contributions on synthesis [16] and the response of a composite to liquid-phase pulse impact treatment [17].…”