The effect of low cooling rates on dendrite morphology during directional solidification in Mg-Gd alloys: In situ X-ray radiographic observation

The real time microstructure evolutions of directional solidification in Mg-Gd alloys are obtained by synchrotron X-ray radiography, and the effects of different low cooling rates under a fixed thermal gradient are studied. Different from the organic alloys, the growth direction of columnar dendrites gradually rotates to the direction of the thermal gradient as the cooling rates increase, which is attributed to the difference of undercooling. Meanwhile, the interface velocity increases but the mean dendrite spacing decreases, and the morphology varies with implication for solute segregation.