Effect of Melt Superheat and Shear Rate on Viscosity of Aluminium–Silicon Alloys

Abstract In this study, viscosity of Al–Si alloys was measured as a function of melt superheat and shear rate using rotational rheometer. Al-7 wt pct Si, Al-20 wt pct Si as well as Al-7 wt pct Si-2 wt pct Fe alloys were used to conduct viscosity measurements with the same superheat and shear stress applied. The viscosity results then were fitted upon the Arrhenius model. The viscosity values obtained in this study with rotational rheometer were extremely high (for pure Al, viscosity values varied between 1.4 and 0.3 Pa s) and exhibited a shear thinning behaviour. All alloy samples that were tested in this study exhibited a shear thinning behaviour, which means that viscosity reduces when the shear rate increases and reaches a steady state above a certain shear limit.