Tensile creep behavior of a die-cast Mg-6Al-0.2Mn-2Ca-0.3Si (wt.%) alloy

Tensile creep property of a die-cast AMXS6020 (Mg-6Al-0.2Mn-2Ca-0.3Si, wt.%) alloy has been investigated. The as-die-cast AMXS6020 alloy consists of alpha-Mg, Al2Ca and (Mg, Al)(2)Ca eutectics at grain boundaries. MgCaSi and Al8Mn5 intermetallic particles also exist both inside alpha-Mg grains and along the grain boundaries. Tensile creep tests, which were carried out at temperatures from 100 to 225 degrees C and stress range of 30-75 MPa for 100 h, show that the AMXS6020 alloy has excellent creep resistance as compared to commercial Mg alloys. When the temperature is increased from 100 degrees C to 180 degrees C or higher, the creep activation energy, Q, changes from 73 to 191 kJ/mot under the applied stress of 50 MPa. The creep results and TEM analysis of the specimens crept at 150 and 200 degrees C under the applied stress of 50 MPa suggest that the creep is controlled by grain boundary sliding at the temperature below 180 degrees C, while the creep is controlled by cross slip to non-basal planes at the temperature over 180 degrees C.