Microstructure and mechanical properties of Mg-Nd-Zn-Zr billet prepared by direct chill casting

High-quality Mg-Nd-Zn-Zr magnesium alloy billets with diameter of 200 mm were successfully prepared by direct chill (DC) casting. The results show that microstructures of the as-cast billet prepared by DC casting are mainly composed of equiaxed a-Mg and Mg12Nd eutectic compound distributing along the grain boundaries. The average grain size decreases along the radius of the billet. And the alloying elements of Nd and Zn distribute homogeneously across the large billet. The optimum process parameters for DC casting of the Mg-Nd-Zn-Zr magnesium alloy billet with diameter of 200 mm have been experimentally determined as follows: casting temperature 710 °C and casting speed 80 mm/min.