Density, Thermal Expansion and Surface Tension of Liquid Titanium Alloys Measured by Non-Contact Techniques

摘要

Due to the high temperatures involved and the high affinity of Ti for oxygen, determining the thermo-physical properties of liquid titanium and its alloys is a difficult experimental task. One way out of this difficulty is the use of electromagnetic levitation. This technique allows containerless positioning and heating of metallic samples by high frequency, inhomogeneous electromagnetic fields. In combination with non-contact diagnostic tools such as pyrometry and videometry, the thermo-physical properties of liquid titanium alloys can be measured over a wide temperature range, including the undercooled regime. For density measurements, a shadowgraph technique, using illumination of the sample by a laser, was used. Surface tension data were obtained by means of the oscillating drop technique from the frequencies of surface oscillations of levitated drops. These containerless methods have been applied to two important types of alloy, namely Ti-6wt%Al-4wt%V and Ti-44at%Al-8at%Nb-1at%B. A description of the methods, as well as results of the measurements, is presented.