Microstructural morphology and phase structure of rapidly solidified hypereutectic Al-Si alloys

In the present work, rapidly solidified hypereutectic Al-Si-Cu-Mg alloys strips was prepared by single roller melt-spinning method. The microstructures, phase and morphology characteristics of the resultant strips were characterized by means of SEM, TEM and XRD technique. The results show that the grains are refined after rapid solidification processing, and the micro-nanocrystals are formed. Compared with equilibrium solidification, the microstructures are changed obviously. The nucleation and growth of primary silicon are suppressed and primary silicon can not deposited, meanwhile, alpha-Al phase is nucleated which prior to eutectic. Therefore, the microstructures become into the metastable state. The microstructures of the strips are composed of primary micro-nanostructure alpha phase and feather-needles-like (alpha+Si) eutectic which set in the a phase. The mechanism of the formation for microstructures of melt-spinning Al-Si alloy have also been discussed.