Viscosity of Industrially Important Al–Zn Alloys. I-Quasi-eutectic Alloys

Viscosity is a very important property in several fields of materials and metal processing. Many systems are still not fully characterized with regard to their thermophysical property data. In addition, as new alloys are developed or used, viscosity data are necessary to understand the best processing conditions. The data that are available frequently show large discrepancies. The effect of minor constituents is very difficult to model and can have a strong effect on the viscosity. Measurements of the viscosity of Zn–Al alloys, with a quasi-eutectic composition, were performed in the molten state, for temperatures between 690 K and 751 K. The measurements were performed with an oscillating cup viscometer, with an estimated uncertainty of 2 % to 5 %, depending on the alloy. The influence of other minor components, such as Pb, Mn, and Mg, on the viscosity of the alloys is discussed. It was concluded that Pb induces a decrease in viscosity, with Mg having the opposite effect, while the effect of Mn is not significant. All the alloys showed Newtonian behavior in the temperature range studied and a non-Arrhenius temperature dependence of viscosity, as usually found for pure molten metals.