Si coarsening of spray-formed high loading hypereutectic Al-Si alloys in the semisolid state

Coarsening of spray-formed hypereutectic Al-Si alloys in the semisolid state was studied. Three Al-Si alloys, Al-25Si, Al-35Si and Al-45Si, were employed. The effects of convection of the Si particles in the liquid matrix at low solid fractions during the coarsening in the semi-solid state were investigated. The coarsening exponent, n, and the rate constant, K, were determined. The coarsening exponents were found not to be sensitive to the solid fraction and Si content in the Al-35Si and Al-45Si alloys, which, however, were different from that of Al-25Si alloy. The rate constants were found to increase with either increasing solid fraction or decreasing solid faction, depending on the conditions being constant temperature or constant Si content, respectively.