Effect of Melt Superheating Treatment on the Microstructure of as Cast AZ61 Magnesium Alloy

The influence of melt superheating treatment on microstructure of as cast AZ61 magnesium alloy was investigated at the melt superheating temperatures of 750°C, 800°C, 850°C, 900°C and 950°C respectively. The characteristics of dendrite spacing were analyzed and the component uniformity of the alloy was evaluated. The results showed that the melt superheating treatment could significantly refine the microstructure of the alloy. With the increase of the superheating temperature, the dendrite spacing gradually decreased. When the superheating temperature was 900°C, the primary dendrite spacing of 228.8μm and the secondary dendrite arm spacing of 11.2μm could be obtained. The concentrations of Al and Zn elements increased with the position change from the center of a dendrite to its primary dendrite spacing. With the increase of the superheating temperature, the distribution of Zn and Al in the alloy was more uniform under 850°C. The optimized superheating temperature of AZ61 alloy was 850-900°C.