The Analysis of the Compositional Uniformity of a Ti-Al Alloy during Electron Beam Cold Hearth Melting: A Numerical Study

The electron beam cold hearth melting (EBCHM) process is one of the key processes for titanium alloy production. However, EBCHM is prone to cause elemental volatilization and segregation during the melting of aluminum-containing titanium alloys such as Ti-6wt%Al-4wt%V. To gain deeper insights into the physical and chemical phenomena occurring during the EBCHM process, this paper establishes melting process models for the Ti-6wt%Al-4wt%V titanium alloy in a crystallizer with multiple overflow inlets. It examines the evolution of melt pool morphology, flow dynamics, heat transfer, and mass transfer during the casting process. The results indicate that the design of multi-overflow inlets can effectively suppress the longitudinal development of impact pits within the melt pool, thereby preventing the formation of solidification defects such as leaks in the melt. Concurrently, the diversion effect of multi-overflow inlets significantly enhances the elemental homogeneity within the melt pool. At a casting speed of 20 mm/min and a casting temperature of 2273 K, compared to a single overflow inlet, the design with three overflow inlets can reduce the depth of thermal impact pits within the crystallizer by 132 mm and decrease the maximum concentration difference in the Al element within the crystallizer by 0.933 wt.%. The aforementioned simulation results provide a theoretical basis for the control of metallurgical and solidification defects in large-scale titanium alloy ingots.