Creep Characteristics of Ca-Added Die-Cast AM50 Magnesium Alloys

Creep characteristics of the die-cast AM50 magnesium alloy containing 1.7mass%Ca were investigated in the temperature range of 150-225DGC. The as-cast microstructure of the alloy consists of a globular *a phase surrounded by a Mg-Al-Ca ternary intermetallic phase. Each creep curve exhibits three stages: a normal transient creep stage followed by a minimum creep rate stage and finally an accelerating stage. The stress exponent of the minimum creep rate, n, is 10 and markedly increases at the yield stress. The activation energy for the creep is 142 kJ/mol, which is close to the activation energy for the lattice self-diffusion of magnesium. These creep characteristics indicate that the creep of the AM50 alloy containing Ca is controlled by a dislocation climb in the *a grains.