The Microstructure and Mechanical Properties of AZ31-xRE Magnesium Alloys

Abstract

The effect of Ce-rich mischmetal (RE) contents on microstructures and mechanical properties of the AZ31-xRE (x=0, 1, 2 or 3 mass%) magnesium alloys is investigated. The constituent phases of AZ31 are α-Mg and few β (Mg₁₇Al₁₂). The intermetallic phase, Al₁₁RE₃, is precipitated in the α-Mg matrix after adding the RE into the AZ31 alloy. The amount and the granule size of Al₁₁RE₃ precipitates increase with increasing the contents of RE added in the alloy. The hardness of the AZ31-xRE alloys also increases with increasing the adding amounts of RE. The superior thermal stability of the Al₁₁RE₃ intermetallic can suppress the grain growth of AZ31-xRE alloys, thus the reduction of hardness of RE-containing alloys after solid solution treatment is less than that of the AZ31 alloy. The results of compression tests show that AZ31-xRE alloys present an inferior deformability and are fractured by the crack propagation along the direction of 45° with respect to the compression axis at room temperature. The compression formability of AZ31 is better than that of RE-containing alloys at the temperature above 473 K. The flow stress of testing alloys increases with increasing the strain rate, but with decreasing the compression temperature.