Kinji Hirai

Mechanical Properties of Twin Roll Cast AZ91 Magnesium Alloy at Room Temperature

Twin roll casting process combines casting and hot rolling into a single process. In this study, mechanical properties at room temperature and microstructure of the twin roll cast AZ91 magnesium alloy are investigated. The alloy exhibited a good combination of high ultimate strength of 343MPa, yield stress of 224MPa and elongation to failure of 13%. The mechanical property was very excellent compared with AZ91 die-cast alloy. EPMA analysis reveals that the Al concentration in Mg matrix is higher in twin roll cast alloy than that in die-cast alloy. This high Al concentration must be the origin of the good mechanical properties of twin roll cast alloy at room temperature.

Effect of Ca and Sr Content on Elevated Temperatures Mechanical Properties of a Cast AZ91 Magnesium Alloy

The effect of Ca and Sr content on the microstructure and mechanical properties of a cast AZ91 magnesium alloy is investigated. Ca and Sr additions in AZ91 magnesium alloy are expected high creep resistance. The microstructure of the alloy exhibits the dendritic α-matrix and the second-phases forming networks on the grain boundary. Tensile tests at elevated temperatures between 448 and 523K reveal that the creep resistance was improved with increasing the additional amount of Ca, especially more than 1.0wt%. From the perspective of grain refinement effect, it is expected that the additions of Ca and Sr to AZ91 magnesium alloy not only improve creep resistance but also improve mechanical properties at room temperature.