Engineering a More Efficient Zirconium Grain Refiner For Magnesium

Zirconium is currently used as a grain refiner for high temperature magnesium alloys. However, currently around 1 wt% is used for grain refinement, and much of this is wasted as sludge due to settling, as zirconium has a density almost four times that of magnesium. Since a recent study suggested that only faceted particles were activated as nucleation sites during casting solidification, ECAE processing of a magnesium-15wt% zirconium grain refiner master alloy was attempted to try to increase the number of faceted particles. ECAE processing of the master alloy only resulted in a modest decrease in grain size, even though the percentage of faceted particles doubled as a result of ECAE processing, since only 1.6% of zirconium particles in the as-received master alloy were faceted and deemed to be likely nucleation sites. The results from this work provide insights for the future development of more efficient grain refiners.