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 °C-175 °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 °C and 70 MPa was only 82.4 h corresponding to the large creep rate 1.6841 × 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 ε˙=2.6067×10−10σ5.623exp(−50510/RT) and ε˙=3.7708×10−8σ3.901exp(−60820/RT), respectively.