Deformation behavior of semi-solid A356 Al-Si alloy at low shear rates: Effect of fraction solid

Abstract

Conventional casting was employed to produce semi-solid metal, SSM, billets of A356 Al-Si alloy. The rheological behavior of the as-cast SSM billets was studied using the parallel plate compression viscometry. The compression tests were carried out at different applied pressures, billet temperatures and fractions solid. The rheological studies were conducted assuming the SSM slurry behaving as Newtonian or non-Newtonian fluid. The calculated viscosity numbers confirmed the pseudoplastic behavior of the SSM billets and were correlated to fraction solid and shear rate, through an empirical equation, to highlight the effect of metallurgical and process parameters on the viscosity of the SSM A356 alloy.log η = 5.56 - 1.38 fs - (1.56 fs + 0.14) log over(γ, {ring operator}), 0.33 < fs < 0.46. This equation is valid at very low shear rates, less than 0.01 s-1. © 2007.