Effects of aging on the microstructures and mechanical properties of extruded AM50 + xCa magnesium alloys

The effects of aging treatment on the microstructures and mechanical properties of extruded AM50 + xCa alloys (x = 0, 1, 2 wt.%) were studied. The results indicated the secondary phase Mg17Al12 precipitated from the saturated α-Mg solid solution while Al2Ca changed slightly when the aging time was increased. The hardness of extruded AM50 + xCa alloys increased initially to its peak, and then dropped to reach its original hardness with the increase in aging time. With the increase in aging temperature, the hardness of the AM50 + 2Ca alloy decreased, whereas the hardness of AM50 and AM50 + 1Ca alloys decreased in the initial stages of aging treatment and increased in the later stages of aging treatment. The tensile strengths of AM50 and AM50 + 1Ca alloys increased after aging treatment for the precipitation of Mg17Al12 phase, which increases the resistance against dislocation movement at the grain boundary; with increase in aging temperature, their tensile strengths increased. For AM50 + 2Ca alloy, the tensile strength declined after aging at 150°C and 175°C, while it increased slightly at 200°C. The ductility of AM50 + xCa alloys (x = 0, 1, 2 wt.%) declined after aging treatment.