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UBC Theses and Dissertations

Melting of solids in liquid titanium during electron beam processing Ou, Jun


Both experiments and numerical modeling work have been carried out to understand the phenomena contributing to the melting of solid condensate in liquid titanium alloys during Electron Beam Cold Hearth Re-melting (EBCHR). To begin, ice/water and ethanol/water analogue physical models were adopted to study the melting of a low melting point solid introduced into liquid and to provide data suitable for developing a comprehensive numerical-based modeling framework. The results revealed that thermal and compositional driven buoyancy and surface tension (Marangoni) flows, when present, can have a significant impact on solid melting in a system where forced convection is not significant. In work that followed, the melting behavior of Commercial Purity Titanium (CP-Ti) rods in liquid CP-Ti was investigated with the aid of an Electron Beam Button Furnace (EBBF) to examine the melting kinetics in the titanium system in the absence of compositional effects. The results showed that the liquid titanium initially froze onto the cold rod when it was immersed, resulting in the formation of a solid/solid interface that acted to retard melting when present. Data collected from the experiments included the evolution in the solid profile of the rod with time and the evolution in temperature obtained from a thermocouple embedded in the rod. The numerical modeling framework developed for the ethanol/water system was modified and applied to support analysis of the experimental results including the determination of an effective interfacial heat transfer coefficient (EIHTC). A similarity solution was also developed to assess the numerical model derived EIHTC. In the final phase of the study, work was conducted on Ti-Al solid rods partially immersed in liquid CP-Ti and liquid Ti-6wt%Al-4wt%V (Ti64) as a means of approximating the behavior of condensate in industry. The melting behavior of Ti-Al was observed to differ significantly from that of CP-Ti rods. Despite having a lower melting point, the Ti-Al rod was found to heat up and melt at a much slower rate. Metallographic examination of partially melted rods and a sensitivity analysis conducted with the numerical model has been able to partially, but not fully explain this difference.

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