Effect of Ca and Ce on Growth of Dendrite α in Magnesuim Alloys

The effect of adding Ca or Ce into Mg-6Al-0.6Zn-0.3Mn alloy on the morphology of dendrite α phase during solidification process was investigated by liquid quenching. The volume fraction of α phase and the characteristic parameters were also measured. The results indicated that Ca addition can promote the nucleation of α phase and restrain the growth of dendrite α. But Ce addition restrained the nucleation of α phase and promoted the growth of columnar dendrite α. It was found that Ca addition and Ce addition both can restrain the coarsing of the secondary dendrite arms and decrease the secondary dendrite arm spacing.