Effect of Pr addition on microstructure and mechanical properties of AZ61 magnesium alloy.

To improve the strength, hardness and heat resistance of Mg-6Al-1Zn (AZ61) alloy, the effects of Pr addition on the as-cast microstructure and mechanical properties of AZ61 alloy were investigated at room and elevated temperatures by means of Brinell hardness measurement, optical microscope (OM), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), X-ray diffractometer (XRD) and DNS100 electronic universal testing machine. The results show that the microstructures of Pr-containing AZ61 alloys were refined, with primary β -Mg17Al12 phase distributed homogeneously. When the addition of Pr is up to 1.2wt.%, the β phase becomes finer, and new needle-like or short-rod shaped Al11Pr3 phase and blocky AlPr phase appear. As a result, optimal tensile properties are obtained. However, greater than 1.2wt.% Pr addition leads to poorer mechanical properties due to the aggregation of the needle-like phase and large size of grains. The present research findings provide a new way for strengthening of magnesium alloys at room and elevated temperatures, and a method of producing thermally-stable AZ61 magnesium alloy. [ABSTRACT FROM AUTHOR]