Crucible-less Processing of Ti with TiC Heterogeneous Nucleation Site Particles by Electrostatic Levitation

Abstract

In this study, the microstructure, hardness, density, viscosity, and surface tension of molten pure Ti with TiC particles were studied via electrostatic levitation experiments, where the electrostatic levitation experiment involved container-less processing, which can suppress heterogeneous nucleation via crucibles. Microstructural observation revealed long needle-shaped α-grains across the whole area in the pure Ti sample. On the other hand, smaller needle-shaped α-grains were found in the samples with TiC particles. However, the detailed microstructural analysis of Ti + 0.7vo l%TiC sample revealed that the fine α-grains observed in the Ti + 0.7vo l%TiC are transformed from single grain of prior β phase. This is because the TiC particles dissolve into the molten Ti during the electrostatic levitation experiment. Instead, Ti–rich TiC precipitates formed by cooling can act as pinning sites rather than heterogeneous nucleation sites, which results in a finer microstructure for the samples with TiC particles during the electrostatic levitation experiment. The density of the samples is linearly related to the temperature, and it decreases with increasing temperature. In addition, a higher density is observed for the samples with TiC particles. Although linear relationships between the surface tension and temperature were found, the addition of TiC particles had no notable effect on the viscosity of the molten pure Ti.