UNIDIRECTIONAL SOLIDIFICATION OF AL-SI EUTECTIC WITH THE ACCELERATED CRUCIBLE ROTATION TECHNIQUE

The accelerated crucible rotation technique (ACRT) is applied to Al-Si eutectic to reveal the effect of forced convection on the unidirectional solidification structure. Experimental results show that if the crucible rotation is started from the beginning of the unidirectional solidification, irregular eutectic with short bars and chunks of silicon will be formed. But if a normal Bridgman process is experienced before the crucible rotation is applied, a more satisfactory directional needle-like silicon structure where the silicon is straight, long, and more regular will be formed during the ACRT process. In order to get a satisfactory unidirectional needle-like silicon structure. ACRT must be used with suitable solidification parameters (temperature gradient G and growth rate R). The rotation method of the crucible is also important.