On the role of orifice wetting for Al and Al22.5 wt%Cu with Al2O3 in the discharge crucible method

The demand to develop Materials Genomics and Integrated Materials Computation requires the availability of high temperature liquid metals property data. As computing power and algorithms are constantly being improved, the accuracy of thermophysical property data has emerged as one of the limiting factors. Knowledge of these properties for materials such as Al and Al-alloys is a critical factor in numerical simulations and modelling of a wide array of industrial processes. This work reports on the measurement of viscosity, surface tension and density of liquid Al and Al-22.5wt.%Cu using the discharge crucible method. While viscosity and surface tension proved to be in good agreement with other published experimental data, as well as various theoretical and empirical models, density was found to be significantly lower than expected or previously measured. With further analysis, it was determined that wetting of Al or Al-Cu at the orifice of the Al2O3 crucible had a significant effect on flow rate; ergo, violating some of the key assumptions in the model used to calculate the thermophysical properties. Dimensionless number analysis identified that wetting had an immediate effect on the flow rate due to the formation of a meniscus, with the effect becoming more dominant as Capillary number decreased or drain time increased. In looking at the sensitivity of the model, it was determined that density had the largest influence on flow rate, explaining the unique link between the role of orifice wetting and density measurement accuracy (as opposed to viscosity or surface tension). Future research will aim to extend the discharge crucible model and method to account for wetting at the orifice, particularly at high temperatures. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study measured the viscosity, surface tension, and density of liquid Al and Al-22.5wt.%Cu using the discharge crucible method. It was found that the density was significantly lower than expected, possibly due to wetting of Al or Al-Cu at the orifice impacting the flow rate. Further research will focus on extending the discharge crucible model to account for wetting at high temperatures.