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

Abstract

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 α-Mg, Al2Ca and (Mg, Al)2Ca eutectics at grain boundaries. MgCaSi and Al8Mn5 intermetallic particles also exist both inside α-Mg grains and along the grain boundaries. Tensile creep tests, which were carried out at temperatures from 100 to 225 °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 °C to 180 °C or higher, the creep activation energy, Q, changes from 73 to 191 kJ/mol under the applied stress of 50 MPa. The creep results and TEM analysis of the specimens crept at 150 and 200 °C under the applied stress of 50 MPa suggest that the creep is controlled by grain boundary sliding at the temperature below 180 °C, while the creep is controlled by cross slip to non-basal planes at the temperature over 180 °C.