Influence of sub-rapid solidification on microstructure and mechanical properties of AZ61A magnesium alloy

The microstructure of sub-rapid solidification processed AZ61A magnesium alloy was presented and discussed. The results show that the grain size of the foil is significantly refined, and the grain morphology is cellular or globular. The eutectic transformation L→α-Mg+β-Mg17Al12 and microsegregation in conventionally solidified AZ61A alloy are suppressed to a great extent. The β-Mg17Al12 phases located in the α-Mg grain boundaries are largely decreased due to high solidification cooling rate. As a consequence, the alloying elements Al, Zn, Mn show much higher solid solubility and the sub-rapid solidification microstructure dominantly consists of supersaturated α-Mg solid solution. The mechanical properties and fractographic analysis reveal that the fracture mechanism and corresponding morphology of the rapture surface of tensile bars are linked to the microstructure obtained and depend on the sub-solidification processes.