Effect of processing on stress-corrosion behavior of die-cast Mg-Al alloy

The effect of processing and microstructure on the stress-corrosion-creep behavior of die-cast rheoformed and conventional AZ91D Mg alloy was studied. Rheoformed alloy has a globular microstructure as compared with a dendritic microstructure of conventional die-cast Mg alloys. The rheoformed die-cast alloy was obtained by stirring the melt during the solidification in a spinning crucible at the casting temperature 580 °C, where the solid fraction amounted to about 40-60%. Due to the difference between the microstructure of Mg alloys produced by the two methods, the corrosion rate of rheoformed AZ91D alloy in the corrosive 0.9% NaCl and in the borate buffer solutions was significantly less than that of a conventional dendritic die-cast alloy. Due to the delay of metal dissolution, creep life of anodized rheoformed alloy in 3% Na₂SO₄ solution was more than an order of magnitude longer than that of an uncoated alloy.