Growth of Si particles and Al dendrites during solidification of a hypereutectic Al-Si-Cu alloy

Abstract Hypereutectic Al-Si alloys containing up to 16-20 wt% Si and often several Cu are widely applied in automobile aerospace industry, because of their high wear resistance high-temperature resistance. The mechanical physical properties these strongly influenced by the size morphology primary silicon particles. Here, rod-like bulk samples hypereutectic Al-18wt%Si-10wt%Cu were solidified a Bridgman-Stockbarger furnace with different solidification parameters. Microstructure analysis longitudinal radial cross-sections demonstrated nearly equiaxed growth Silicon particles 3D samples. At low cooling rate few but larger exist compared many smaller for higher rate. Also structure Al dendrites is much finer at rates. Additionally, sheet-like under isothermal conditions. A real-time observation method using X-ray radiography allowed in-situ observation. During down below liquidus temperature, facetted first nucleate. Reaching nucleation temperature Al, non-facetted was observed simultaneously whole melt, generally not starting from surface existing Some growing plane develop rather rapidly one direction, whereas other grow more equiaxed, which attributed grain orientations Al-rich quasi-2D solidification.