Effects of Al-10Sr master alloys on grain refinement of AZ31 magnesium alloy

The effects of Al-10Sr master alloys on grain refinement of AZ31 magnesium alloy were investigated, and the refinement efficiency of different Al-10Sr master alloys (commercial, solubilized, rolled and remelted+rapidly cooled) was compared and analyzed. The results indicate that the morphology and size of Al4Sr phases in the microstructures of different Al-10Sr master alloys, are of great difference. For the commercial Al-10Sr master alloy, the Al4Sr phases evolve from coarse block shape to relatively fine block shape after being dissolved at 500 °C for 4 h and followed by water quenching; but after being rolled at 300 °C for 50% reduction or remelted and followed by rapid cooling, the Al4Sr phases mainly exhibit fine granule and fibre shapes. In addition, the different Al-10Sr master alloys can effectively reduce the grain size of AZ31 magnesium alloy, but their refinement efficiency is different. The refinement efficiency of the Al-10Sr master alloy obtained by remelting and rapid cooling is the best, then the rolled, solubilized and commercial Al-10Sr master alloys are in turn. The difference of refinement efficiency for different Al-10Sr master alloys may be related to the dissolution rates of Al4Sr phases with different morphologies and sizes in the melt of AZ31 magnesium alloy.