Dendritic Growth in Mg-Based Alloys: Phase-Field Simulations and Experimental Verification by X-ray Synchrotron Tomography

Changes in polycrystalline dendritic growth patterns during solidification result in a variety of solidified dendritic structures and morphologies. These microstructural changes are induced by a variety of effects such as the random distribution of nucleation sites and orientations, the interaction of growing individual dendritic grains, and effects of solid-liquid interfacial energy anisotropy. Here, we have studied the formation of the complicated and diverse dendrite morphologies both experimentally, by electron backscatter diffraction and by X-ray tomography; and numerically by three-dimensional phase-field simulations. Three binary magnesium alloys were considered in this study: Mg-Al, Mg-Zn, and Mg-Sn alloys. We show that the solidification microstructure can be attributed to the following factors: The interaction of the growing dendrites, the anisotropy of the growth, and the distribution and initial random orientations of nucleation sites.