A new approach to designing a grain refiner for Mg casting alloys and its use in Mg-Y-based alloys

摘要

A totally new grain refiner, Al_2Y, for cast Mg alloys has been predicted using the recently developed edge-to-edge matching (E2EM) crystallographic model. An addition of 0.6-1.0 wt.% Al into the Mg-10 wt.% Y melt promotes the in situ formation of Al_2Y, which reduces the average grain size from about 180 to 36 μm. Active nucleation Al_2Y particles were reproducibly observed at the centres of many refined grains. The excellent grain-refining efficiency is comparable to that of Zr for the same alloy, but the thermal stability of the grains refined by Al_2Y is much higher than those refined by Zr up to a temperature of 550 °C for 48 h. The mechanisms of grain refinement and the superior thermal stability of the refined grains due to Al addition in the Mg-Y alloy are discussed based on the current experimental results.