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, Al 11RE3, is precipitated in the α-Mg matrix after adding the RE into the AZ31 alloy. The amount and the granule size of Al 11 RE3 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. © 2007 The Japan Institute of Metals.