Microstructural Changes in Hypoeutectic Al–Si Alloys by Low Shear and Vibration Induced Melt Conditioning Setup

摘要

In the present work, refinement of microstructure in hypoeutectic Al–Si alloys, i.e., A356 and Al–7wt%Si has been reported. One of the mechanical technique, melt conditioning, was used to refine the microstructure. The technique involved subjecting the melt to low shear force by passing it through a slope at a temperature above its liquidus temperature. In addition to the shear force, vibration was induced into the melt during its flow by a simple setup for melt conditioning. Shear force along with vibrations led to enhanced refinement in both the alloys, the most prominent being A356 alloy. It has been suggested that higher fraction of fragmented oxide particles/films into the molten A356 alloy during the flow before solidification in the mould could enhance the nucleation centres. It was concluded that the bi-oxides such as MgAlO~(4)acted as effective heterogeneous nucleants for α-Al.