Non-Equilibrium Phase Crystallization of Al–Si Alloy Close to Eutectic Composition by Mechanical Vibration

The amount of the primary phase crystallized in a eutectic alloy at a set cooling rate is determined by the alloy composition. Only a small amount of the primary phase can be crystallized in a near-eutectic composition alloy. Here we show an interesting phenomenon in which the microstructure is changed by the application of mechanical vibration to a near-eutectic Al–Si alloy during cooling from the molten metal to the semi-solid state. The amount of primary α-Al phase can be obtained with the application of mechanical vibration is more than equilibrium solidification. The amount of non-equilibrium α-Al phases, which is more than the amount with equilibrium solidification, increases with the velocity amplitude of the vibration. The non-equilibrium α-Al phases had uniform shape that consisted of fine spherical particles. These non-equilibrium α-Al phase crystals had the same composition as the primary α-Al phase crystals solidified without vibration. Primary Si particles could also be observed by the application of mechanical vibration.