Creep Resistance of Die-Cast Mg-Al-Base Alloys

The deformation resistance under creep conditions was investigated at temperatures up to 150 deg C for the high-purity die-cast alloys AZ91, AS21, AS41, AM60 and AE42. Results are reported for the work hardening at constant strain rate of 10 exp -3 /s up to a certain stress and the subsequent creep. The influence of temperature on creep can be described on the basis of thermal activation with a single apparent activation energy of about 135 kJ/mol. Comparison of the times for creep by strains Delta epsilon = 0.003, 0.01, and 0.05 indicate that die-cast AZ91 has a relatively good creep resistance at temperatures up to 150 deg C compared to annealed AZ91 as well as the other investigated die-cast Mg-Al-base alloys at stresses above 100 MPa. Below 100 MPa the creep resistance of AS21 and AS41 is distinctly better than that of AZ91, probably due to better precipitation hardening.