Industrial grade versus scientific pure : Influence on melt properties

Abstract

Viscosity, density, and the undercooling ability of the Zr-based bulk glass forming melt, which was manufactured in two different degrees of purity, have been studied. Investigations have been carried out by means of Couette rheometry and electrostatic and electromagnetic levitation with the latter under microgravity conditions. We found that oxygen and impurities present in industrial grade metals do not significantly alter the melt viscosity and density, while they clearly affect the undercooling ability. Comparing container based and containerless results showed that Couette rheometry can be applied in the temperature range between 1150 K and 1375 K, where it provides reliable data, but only at a rather low oxygen content. Higher oxygen contents, as in the case of the industrial grade alloy, cause measurement artefacts. In the case of Zr59.3Cu28.8Al10.4Nb1.5 alloys, these findings allow a better localization of the key factors dominating the glass forming ability.