Abstract
The surface tension and viscosity are defined as the attraction between the molecules of the melt and the friction of fluids in motion, respectively. Both terms are considered to be dominant factors in various metallurgical phenomena, including embracing gas absorption, nucleation of gas, nucleation and growth of non-metallic inclusions, and surface oxide/melt reactions. In this study, therefore, the experimental measurements of melt properties for several metals, including pure Al, Al alloys and Mg-Al alloys (AZ91 & AM60), were assessed with variation of temperature and alloying element concentration. The surface tension and the viscosity of individual melts have been measured, using the ring method and the rotation method, under either pure Ar or SF6+CO2 atmosphere. The primary results through present experiment showed that both properties of these metals decreased with increasing temperature. The addition of elements to both pure Al and Mg also decreased the surface tension and increased the viscosity. The optimum viscosity was evaluated for different alloy melts, including Al-Si, Al-Mg, Al-Cu. In detail, greater than 1.5 wt% for Al-2wt%Mg melt, 2~2.5 wt% for Al-1wt%Si melt, and 1.5 wt% for Al-4wt%Cu melt. The surface tension values of Mg alloys were less than 500~600 (mNm-1). However, the optimum viscosity values for both alloy melts were obtained with 1.5wt% Ca addition and more than stirring time of 10 min.
