Abstract: The creep property and mechanism of AZ31 magnesium alloy under high temperature and low stress is investigated. The results show that the creep curve presents obviously the three stages creep characteristic. The creep rate increases and the static creep stage shortens with increasing temperature and stress. When temperature is above 420℃, the creep of AZ31 magnesium alloy under lower stress is COBLE creep controlled by grain boundary diffusion of magnesium; however, at higher stress the creep accords with WEETMAN creep controlled by dislocation climb. The creep of AZ31 magnesium alloy is controlled by dislocation glide at temperature ranging from 320～420 ℃. The critical stress cr which results in changing from COBLE creep to WEETMAN creep is calculated, the magnitude of cr and the Nabarro-Peieris stress p has the relation as follows：cr≈(2～3)p.

Key words: AZ31 magnesium alloy, Creep mechanism, High temperature creep