Hardening and Softening in Magnesium Alloys

Abstract

There is an increasing interest in automobile and aerospace industries for lightweight materials (alloys and metal matrix composites). Magnesium alloys with their high specific strength (the strength-to-density ratio – ┫/ρ) may be used as structural materials. Over the last two decades, use of magnesium alloys has progressively grown. Different magnesium alloys have been developed and tested. Research and development of magnesium alloys have shown that they have a great potential for applications as the lightweight materials. This is because of their high specific strength, high damping capacity and good machinability. However, their applications are limited at elevated temperatures. New alloys with improved creep resistance and high strength have been developed in recent years. Among the alloys, the Mg-Al-Ca and Mg-Al-Sr alloys exhibit good creep resistance due to the presence of thermally stable phases. During plastic deformation over wide ranges of temperature and strain rate, different micro-mechanisms may play important role. It is important to estimate the mechanisms responsible for the deformation behaviour – hardening and softening – of the alloys. An analysis of deformation microstructures has shown that one should consider dislocation-based mechanisms in order to explain the deformation behaviour. The values of strength may be influenced by different hardening mechanisms. The aim of this paper is to present the deformation behaviour of some magnesium alloys at different temperatures and to propose the mechanisms responsible for plastic deformation of the alloys.