Non-dendritic Structural Changes in Al–7Si Alloy Cast Through Rapid Slurry Formation (RSF) Process

Abstract

Rapid slurry formation (RSF) is a semi-solid metal forming technique,which is based on a so-called solid enthalpy exchange material.The beauty of the process is that the slurry is controlled by relative added amounts of the alloy system used. It is not necessary to accurately control the heat flux to surrounding media such as, crucible or mould. In the present investigation 15 % solid fraction in Al–7Si alloy slurry has been produced by RSF method. The slurry so preparedwas cast in gravity die cast mouldwith water cooling arrangement. Thus ingot of size 30 cm 9 5 cm 9 2.5 cmcould be produced. The microstructure showed rosette and globular type a-Al morphology. Tensile properties evaluated were higher than as cast Al–7Si alloy. During slurry formation coarsening of particles was experimentally investigated and also theoretically described by Lifshitz-Slyozov-Wagner (LSW) theory and convective mass flow equations.