Surface tension of substantially undercooled liquid Ti-Al alloy

It is usually difficult to undercool Ti-Al alloys on account of their high reactivity in the liquid state. This results in a serious scarcity of information on their thermophysical properties in the metastable state. Here, we report on the surface tension of a liquid Ti-Al alloy under high undercooling condition. By using the electromagnetic levitation technique, a maximum undercooling of 324 K (0.19 T_L) was achieved for liquid Ti-51 at.% Al alloy. The surface tension of this alloy, which was determined over a broad temperature range 1429-2040 K, increases linearly with the enhancement of undercooling. The experimental value of the surface tension at the liquidus temperature of 1753 K is 1.094 N m^-1 and its temperature coefficient is -1.422 10^-4 N m^-1 K^-1. The viscosity, solute diffusion coefficient and Marangoni number of this liquid Ti-Al alloy are also derived from the measured surface tension.