Kinematic viscosity of liquid Al-Cu alloys

Abstract

Temperature dependences of kinematic viscosity v of liquid Al100-x-Cu-x 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 degrees C and isothermal expositions of 10 to 15 minutes during both heating up to 1100-1250 degrees 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 degrees C at 10 and 17.1 at.% Cu, 1050 degrees C at 25 and 40 at.% Cu, 850 degrees 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 degrees C. An abnormally high spreading of results at repeated decrement measurements was fixed at heating of the alloy containing 50 at.% Cu above 1000 degrees C. During subsequent cooling the effect disappeared. Isotherms of kinematic viscosity have been fitted for several temperatures.