Preparation and compositional distribution of a TA17 titanium alloy ingot via a novel semi-continuous induction melting process

Abstract

A novel semi-continuous induction melting technology for the production of large-volume titanium alloy ingots was introduced. The effects of the melting power and ingot drawing speed on the production process of titanium alloy ingots via this technology were systematically investigated. The results show that insufficient melting power or excessive drawing speed leads to failure in alloy melting, whereas excessively high melting power or overly slow drawing speed causes overheating of the cooling circulation system, leading to equipment failure. Optimal conditions are achieved at a melting power of 750 kW and an ingot drawing speed of 4 kg·min−1, resulting in efficient production of titanium alloy ingots with an energy utilization rate of 8.3%. Under these conditions, a 522 kg TA17 titanium alloy ingot with a diameter of 280 mm was successfully produced. The aluminum content distribution in the TA17 titanium alloy ingot was analyzed, and the results indicate that the aluminum content does not vary significantly along the axial direction. However, a slight decreasing trend in the aluminum content is observed from the edge to the center in the radial direction, with all variations confined within ±0.1wt.%. Microstructural analysis via optical microscopy reveals a transition from acicular to flaky grain structures from the edge to the center of the ingot in the radial direction. Furthermore, the grain size across the ingot cross-section exhibits a gradient distribution characteristic, decreasing progressively from M-6.5 (approximately 52.5 µm) at the center region to M-6.0 (about 44.2 µm) near the edge. This microstructural heterogeneity primarily originates from the temperature distribution during solidification. The higher temperature and slower cooling rate at the ingot center provide favorable conditions for grain growth, whereas the rapid heat dissipation at the edge due to contact with the crucible significantly enhances nucleation rate and suppresses grain growth, ultimately resulting in refined microstructure.