Coupling in situ synchrotron X-ray radiography and phase-field simulation to study the effect of low cooling rates on dendrite morphology during directional solidification in Mg-Gd alloys

The effect of low cooling rate with a fixed temperature gradient during directional solidification of Mg-Gd alloys is investigated by coupling in situ X-ray synchrotron radiography and phase-field method. Results show that the primary dendrite spacing decreases with the increase of cooling rates, and the relationship between the logarithm of primary dendrite arm spacing and the logarithm of cooling rate is linear. After fitting, the slope of primary dendrite arm spacing is -0.71, while that of phase field simulation is -0.74, which indicates the experimental statistics are basically consistent with that of phase field simulation. The simulation thoroughly studies the kinetic transition process of seaweed-like morphology and the evolution of solute distribution for dendrites, both the solid volume fraction and the velocity of liquid-solid interface increase with the increase of cooling rate. The simulation is in good agreement with experimental results. (C) 2019 Elsevier B.V. All rights reserved.