Effect of Y and Ca addition on the creep behaviors of AZ61 magnesium alloys

The creep behaviors of AZ61-1.2Y and AZ61-1.2Y-1.0Ca alloys under the temperature 125 degrees C-175 degrees C and the applied stress 50-70 MPa for 100 h were investigated in a typical creep testing machine. The stress exponent n at different stresses and creep activation energy Q at different temperatures for the two alloys were discussed also. Results showed that the creep resistance of AZ61 alloy can be significantly improved by the addition of Y and Ca. The steady creep rates of AZ61-1.2Y and AZ61-1.2Y-1.0Ca alloys increased obviously with increasing applied stress and temperature. The creep rate of AZ61-1.2Y alloy was significantly larger than that of AZ61-1.2Y-1.0Ca alloy under all experimental conditions. The creep life of AZ61-1.2Y alloy under 150 degrees C and 70 MPa was only 82.4 h corresponding to the large creep rate 1.6841 x 10(-7). But the creep life of AZ61-1.2Y-1.0Ca alloy was always greater than 100 h, exhibiting excellent creep resistance at this experimental condition. The creep constitutive equation of AZ61-1.2Y alloy and AZ61-1.2Y-1.0Ca alloy can be expressed as (epsilon)over dot = 2: 6067 x 10(-10) sigma(5.623) exp(-50510/RT) and (epsilon)over dot = 3.7708 x 10(-8) sigma(3.901) exp(-60820/RT), respectively. (C) 2016 Elsevier B.V. All rights reserved.