Dissolution Behavior of TiC Heterogeneous Nucleation Site Particles in Ti–6Al–4V in Electrostatic Levitation Method
摘要
Clarifying the dissolution behavior of titanium carbide (TiC) during heating is crucial for establishing suitable heating conditions for prior-β grain refinement of Ti–6Al–4V induced by TiC particles. This study aims to reveal the effects of heating in the electrostatic levitation (ESL) experiments on the dissolution of TiC by establishing the dissolution kinetics of TiC in liquid Ti–6Al–4V. The sintered mixture of Ti–6Al–4V powder and TiC particles was melted and solidified in ESL. The integral value of heating, I (T, t), with the temperature and heating time serves as a valuable index of the amount of heating. The amount of residual TiC, MR, decreases exponentially with the increase of I (T, t), indicating the symmetry of the Johnson–Mehl–Avrami–Kolmogorov equation. A phase field simulation of TiC dissolution revealed that the dissolution time increases in proportion to the 1.8th power of the initial particle diameter. Additionally, the value of MR calculated using the dissolution equation based on the diffusion theory was consistent with the results of the ESL experiments at a diffusion coefficient, D, of about 1 – 3 × 10−11 m2 s−1, which is an intermediate value of D in multiple diffusion forms. The dissolution model also estimates the number of TiC particles which work as the nucleation sites (Active-TiC).