Effect of Cooling Rate on the Grain Refinement of Mg-Y-Zr Alloys

The grain refinement resulting from the addition of yttrium (Y) (1, 3 pct, and 9 wt pct) and zirconium (Zr) (0.1, 0.2, and 0.5 wt pct) to magnesium (Mg) under a wide range of cooling rates (0.8 to 160 K/s) has been investigated. This study quantifies the effect of Y and Zr on the grain size (d(gs)) of Mg-Y base alloys followed by examination of the effect of cooling rate on these alloys. The Interdependence Model was able to describe the reduction in grain size caused by the growth restriction provided by Y and soluble Zr, and the introduction of potent Zr particles. It is shown that by incorporating a term for cooling rate into the Interdependence model the effect of cooling rate on grain size can be assessed for the range of growth restriction values and cooling rates investigated.