Hardening and softening in deformed magnesium alloys

The deformation behaviour of three commercial magnesium alloys AZ91, AS21 and AE42 has been investigated in a wide temperature range. Specimens were deformed in tension and in compression in the temperature range of 300-573 K at constant but various strain rates. The form of the stress-strain curves is very sensitive to the test temperature and the strain rate. The deformation behaviour of the specimens can be attributed to the occurrence of hardening and softening during straining. In order to identify hardening and softening processes, the stress dependence of the strain-hardening coefficient was evaluated. Different models describing hardening and softening were used to analyse the observed behaviour. The model proposed by Lukac and Balik can describe the experimental data in the temperature range of 373-473 K. The analysis shows that conservative slip of dislocations is the main recovery process. The yield stress analysis reveals an asymmetry of values obtained in tensile and compression tests. (C) 2002 Elsevier Science B.V. All rights reserved.