Analysis of columnar to equiaxed transition of aluminum alloys by unidirectional solidification experiment and measurement of nucleation undercooling

In the casting of aluminum alloys, fine grains are required to suppress the cracking and quality deterioration. Al-Ti-B alloy is commonly utilized as grain refiner. It is well-known that TiB2 particles are serving as grain refiner. However, the effects of addition amounts of grain refiner and solidification conditions on the solidification structure have not been fully clarified with application of grain refiner. In this study, unidirectional solidification experiments of A1070 alloy have been performed to investigate the effects of additional amounts of grain refiner and solidification conditions on the columnar-to-equiaxed transition (CET). At the same time, the nucleation undercooling in the solidification of A1070 alloy with and without grain refiner, have been also measured. Moreover, Hunt model has been utilized with consideration of the measured results of undercooling to examine the obtained results by unidirectional solidification experiments.