Microstructure and Mechanical Properties of AZ61 Magnesium Alloys with the Y and Ca Combined Addition

Abstract

In this paper, microstructure and mechanical properties of AZ61 magnesium alloys with the Y and Ca combined addition were investigated. The results exhibit that the addition of Y and Ca into AZ61 alloy leads to effective refinement of the microstructure and additional block-like Al2Y and long-rod Al2Ca phases found in AZ61–1.2Y alloy and AZ61–1.2Y–1.0Ca alloy, respectively. The tensile strength, elongation and creep properties of AZ61–Y–Ca alloy are significantly increased by the addition of Y and Ca. The tensile strength of AZ61–1.2Y–1.0Ca alloy at 20 and 175 °C is up to 225 and 175 MPa, and compared with AZ61 alloy, the strengths of the alloy are enhanced by 37 and 80%, respectively. AZ61–1.2Y–1.0Ca alloy achieves the lowest steady creep rate 2.5027 × 10−7 s−1 that is about 4 times lower than that of AZ61 alloy. The poor mechanical properties of AZ61 magnesium alloy is attributed to the softening of β-phase Mg17Al12, especially at elevated temperature. The tensile strength and creep resistance of AZ61–1.2Y–1.0Ca alloy are effectively improved by the Al2Ca and Al2Y phases.