CRYSTALLIZATION OF ALUMINUM-ALLOYS IN THE PRESENCE OF CAVITATION PHENOMENA INDUCED BY A VIBRATING ELECTROMAGNETIC PRESSURE

A new magnetohydrodynamic method of transmitting forced vibrations to solidifying aluminum alloy melts has been developed. Contrary to the c ase of the conventional mechanoacoustic systems, this device lends its elf very well to a fundamental investigation. The relatively accurate knowledge of both the electromagnetic pressure and the local velocity peaks has enabled us to reveal the specific effects of the oscillatory flow and of the cavitation phenomena on grain refinement. It has been shown that the cavitation threshold depends both on the surface state of the crucible internal walls and on the electromagnetic pressure pe ak. In the presence of well-developed cavitation situations, a very fi ne and homogeneous microstructure has been observed throughout the ing ots.