Effect of Ca and Sr on the compressive creep behavior of Mg-4Al-RE based magnesium alloys

The compressive creep behavior of Mg-4Al-RE-1.2Ca (AEC4112) alloy and Mg-4Al-RE-1.2Ca-0.2Sr (AECJ411202) alloy is investigated on a special apparatus. The stress exponent n under different stresses and the creep activation energy Q(c) under different temperatures of AEC4112 alloy and AECJ411202 alloy are estimated by an empirical equation. The results reveal that the compressive creep resistance of Mg4-Al-RE (AE41) alloy is improved significantly by a small amount of Ca and Sr. The steady state compressive creep rates of AEC4112 alloy and AECJ411202 alloy are increased with increasing temperature and applied stress. The steady state compressive creep rates of AEC4112 alloy and AECJ411202 alloy are 2.2817 x 10 (7) mm/s and 1.3041 x 10 (7) mm/s under 150 degrees C and 100 MPa, respectively. The compressive creep resistance is improved by intermetallic compounds Al2Ca, Al2RE and Al4Sr inhibiting the climbing of the dislocation, the sliding and diffusion of the grain boundary. The compressive creep constitutive equations of AEC4112 alloy and AECJ411202 alloy are written as (epsilon) over dot(s1) = 2.0276 x 10 (10) x sigma(5.662)exp(-47447/RT) and (epsilon) over dot(s2) = 5.8208 x 10 (11) x sigma(6.123)exp(-68252/RT) respectively. The compressive creep mechanism of AEC4112 alloy and AECJ411202 alloy is the combined effects of grain boundary diffusion and grain boundary sliding determined by dislocation climbing. (C) 2014 Elsevier Ltd. All rights reserved.