Effect of direct chill casting process parameters on the microstructure and macrosegregation of Mg-Al-Zn ingot

Abstract

It has been demonstrated that the microstructure and macrosegregation of ingot produced by direct chill casting would take remarkable effect on its deformation behavior. In the present study, the influence of casting speed and temperature on the microstructure and macrosegregation of AZ81 ingot prepared by a self-designed crystallizer (220 × 220 mm) was investigated. The results show that the volume fraction of β-Mg17Al12 predicted by the Gulliver-Scheil model agrees well with image analysis results of the ingots prepared at different casting parameters. Moreover, the casting speed affects the macrosegregation greatly while it has slight influence on the distribution of β-Mg17Al12, and the casting temperature has slight influence on macrosegregation of ingot while it has strong influence on the distribution of β-Mg17Al12. The optimal casting speed and casting temperature for the AZ81 ingot are 80 mm/min and 953 K, respectively. The corresponding maximum values of ultimate tensile strength, yield strength and elongation are 265 MPa, 210 MPa and 3.5%, respectively.