Abstract: To carry out a rotational casting method of preparing a silicon eutectic alloy composition, silicon and one or more metallic elements M are melted together to form a eutectic alloy melt comprising the silicon and the one or more metallic elements M. A mold containing the eutectic alloy melt is rotated about a longitudinal axis thereof at a speed sufficient to form a rotating volume of the eutectic alloy melt in contact with an inner surface of the mold. Heat is directionally removed from the rotating volume of the eutectic alloy melt to directionally solidify the eutectic alloy melt, and a eutectic alloy composition, which includes the silicon, the one or more metallic elements M, and a eutectic aggregation of a first phase comprising the silicon and a second phase of formula MSi2, where the second phase is a disilicide phase, is formed.