Creep and Corrosion Properties of the Extruded Magnesium Alloy Containing Rare Earth

Abstract

Effects of microstructures on the creep and corrosion properties were investigated in the Mg-8Al alloys with addition of the rare earth elements (La-rich Mischmetal, RE). The addition of RE to Mg-8Al alloy may form a stable intermetallic phase, Al₁₁RE₃ at elevated temperature, and suppress the β phase (Mg₁₇Al₁₂) with poor stability at high temperature. The corrosion rate of the alloy slightly decreases with increasing the added RE contents. The constant-load creep behavior was examined at 423, 448 and 473 K under stresses between 40 and 100 MPa. The RE-containing alloy showed a prolonged period of stead-state creep compared to the Mg-8Al base alloy and slightly reduced minimum creep rates. A stress exponent of 2 estimated suggests that the creep behavior can be controlled by the grain boundary sliding. The apparent activation energy for creep of Mg-8Al and Mg-8Al-2RE alloys are 114 and 104 kJ mol⁻¹, respectively.