Effect of mould D/H ratio on solidification structure of Al–2·0%Si alloy ingot under ultrasonic vibration

A series of experiments were conducted by Al-2·0Si%Si alloy to investigate the effect of mould D/H ratio and shape on solidification structure under ultrasonic vibration (UV). Finally, the mechanism of grain refining was discussed. The results show that equiaxed grain occupancy is maximized when D/H is equal to 0·7 for ingots with mould volume of 80 and 120 cm3, however, the equiaxed grain occupancy has the maximum when D/H is equal to 2·0 for the ingot with mould volume of 200 cm3. Otherwise, the equiaxed grain occupancy has downtrend with increasing of mould volume. The columnar structure is easily formed in ultrasonic ingots with complex mould shape and more corners.