Kinematic viscosity of liquid Al-Cu alloys

Temperature dependences of kinematic viscosity n of liquid Al100-x-Cux alloys (x = 0.0, 10.0, 17.1, 25.0, 32.2, 40.0 and 50.0 at.%) were measured. A technique based on registration of the period and the decrement of damping of rotating oscillations of a cylindrical crucible with a melt was used. Viscosity was calculated in low viscous liquids approximation. Measurements were carried out in vacuum in crucibles of BeO with a temperature step of 30°C and isothermal expositions of 10 to 15 minutes during both heating up to 1100-1250°C and subsequent cooling. We have discovered branching of heating and cooling curves v(T) (hysteresis of viscosity) below temperatures depending on the copper content: 950°C at 10 and 17.1 at.% Cu, 1050°C at 25 and 40 at.% Cu, 850°C at 32.2 at.% Cu. For samples with 10 and 17.1 at.% Cu the cooling curve 'returns' to the heating one near 700°C. An abnormally high spreading of results at repeated decrement measurements was fixed at heating of the alloy containing 50 at.% Cu above 1000°C. During subsequent cooling the effect disappeared. Isotherms of kinematic viscosity have been fitted for several temperatures.