AbstractMg-Dy alloys are attractive for biomaterial applications. Their mechanical property profile is close to that of cortical bone, they are non-toxic, osseoconductive and degradable. Their macroscopic characteristics depend on their microstructure, which can be tailored through the alloy composition and the solidification parameters. In situ synchrotron radiation diffraction is a tool to unequivocally follow the phase formation and grain growth during cooling, thus determining the solidification sequence. In the present study Mg alloys containing Dy and Zr were investigated to characterize the solidification phenomenon during cooling from 660°C to 200°C. Samples, contained in steel crucibles, were melted in a modified induction furnace for in situ synchrotron radiation measurements at the HZG beamline P07B (HEMS) at PETRA III, DESY, with the temperature controlled by type K thermocouples during the measurements. The results give an experimental validation of the thermodynamic calculations and input for refining the existing thermodynamic models. This contributes to a better understanding of the microstructure evolution thus to control desirable macroscopic characteristics.