The kinematic viscosity of liquid copper-aluminum alloys

The method of damped torsional vibrations of crucible with liquid under investigation is used for measuring the temperature dependences of kinematic viscosity $\nu$ of $\text{Cu}_{100 - x}\text{Al}_x$ melts $(x = 0$–$100$ at.%$)$ in the range of temperatures $t$ between the liquidus and $1100$–$1450^{\circ}$C. Unlike the majority of such experiments, the measurements are performed both in the process of heating the sample after its melting and in the course of subsequent cooling. The branching of $\nu(t)$ curves corresponding to the foregoing modes is revealed below certain temperatures dependent on the composition of sample (viscosity hysteresis). The curves obtained under cooling have a simple exponential shape predicted by activation theories of viscous flow. The obtained temperature dependences are used for constructing isotherms of kinematic viscosity, on which maxima are observed in the vicinity of stoichiometric concentration of $\text{CuAl}_3$ and composition of $\text{Cu}$–$30$ at.% $\text{Al}$. For the same compositions, extrema are observed on the concentration dependence of activation energy of viscous flow.