FABRICATION OF METAL-MATRIX COMPOSITES USING A HELICAL INDUCTION STIRRER

The working principle and the peculiarities of a new electromagnetic r heocaster, which is based on the use of rotating permanent magnets and which allows the production of intense three-dimensional multiphase f lows in solidifying semisolid alloy slurries and metal matrix composit es, are described. This process can be applied to the direct continuou s casting of billets, tubes and slabs and is characterized by very low electric power consumption. Local measurement techniques are applied to the study of the evolution of non-newtonian magnetohydrodynamic mul tiphase flow phenomena with the rotational speed of the inductor, the solid fraction of the aluminium alloy matrix and the size and volume p ercentage of SiC particles. Satisfactory results concerning the micros tructure of solidified aluminium slurries and aluminium matrix composi tes (homogeneity, crystal shape, grain size, fraction of primary solid , distribution of SiC particles) were obtained. A discussion is presen ted relating the metallurgical findings to the heat and three-phase no w measurements.