Influence of Ca and Sr Addition on Impression Creep Behavior of Mg-4Al-RE Alloy

摘要

The impression creep behavior of Mg-4Al-RE-0.8Ca-0.2Sr (AEXJ4110) alloy was investigated under the applied stresses of 55, 75, 95MPa and the temperatures of 398, 423, 448K on a special apparatus. The results showed that the microstructure of AEXJ4110 alloy consisted of acicular Al11La3, granular Al2La, bone shape Al2Ca and fish-bone shape Al4Sr. The impression creep resistance of AE41 alloy was improved by adding Ca and Sr. The primary impression creep depth of AEXJ4110 alloy was increased with increasing applied stress and temperature. The creep strain rates of AEXJ4110 alloy under different stresses and temperatures were a power function of time. The constitutive equation of steady-state impression creep for AEXJ4110 alloy can be written as epsilon s=9.71x10-3(E/T)(sigma/E)4.3exp((-100.449+3368.98(sigma/E))/RT) with stress exponent n 4.3 and creep activation energy Q(c) about 100.449kJ/mol. The impression creep mechanism of AEXJ4110 alloy in the temperature range of 398-448K and stress range of 55-95MPa is controlled by dislocation climb dominated by self-diffusion of magnesium atoms impeded by the precipitated phases with high melting temperatures.