The influence of thermomechanical processing on the strength and the creep behaviour of the age-hardenable magnesium-alloy MgNd2Ag2Zr

Thermomechanical treatment of aluminium and titanium-based light metal alloys is known to be a useful and highly effective process, which offers superior mechanical properties. In contrast there is a lack of equivalent knowledge and experience in the field of magnesium alloys. This situation forms the background of the present work, which has the aim to show the beneficial effects of thermomechanical processing on a commercial age hardenable Magnesium alloy. The main strengthening mechanisms available in the magnesium-alloy considered are work hardening and to a minor extent precipitation hardening. The work hardening capacity is only limited by dynamic recovery, which strongly depends on the starting microstructure. Dynamic recrystallization can not take place under any circumstances, even if high deformation degrees and high deformation temperature are concerned. This is why thermomechanical treatment has a considerable effect on the yield-strength, which amounts to at last twice the yield-strength of fully heat-treated material. Furthermore the thermomechanical treatment is expected to improve the creep behaviour. Considering the creep-strength this is true until the temperature exceeds 100 degrees C. Above this temperature the thermomechanically treated microstructure is not stable and therefore offerns no longer advantages in strength. (IFAM)