Three-dimensional α-Mg dendritic morphology and branching structure transition in Mg-Zn alloys

Three-dimensional dendritic morphology and branching structure of hexagonal close-packed α-Mg in magnesium-zinc alloys possessing different zinc concentrations were studied using synchrotron X-ray microtomography. Interestingly, dendrite growth patterns were observed to undergo a morphologic transition with increasing zinc addition. Dendrite arms in the basal plane of hexagonal close-packed α-Mg tend to split and deviate from the basal plane continuously and symmetrically as a function of zinc concentrations. A hyperbranched dendrite structure was also found with an interim zinc concentration. Several types of dendrite growth patterns with different morphologies and branching structure were proposed in order to reflect the evolution of α-Mg dendrites with various zinc contents.