Influence of the Thermal Treatment Temperature on the Microstructure and Phase Composition of Casts of β-Solidifying TNM Alloy Based on the Ti-Al-Nb-Mo System

摘要

This study is aimed at investigating the influence of hot isostatic pressing (HIP) on the microstructure and phase composition of titanium aluminide-based alloys using experimental and computational methods. Isothermal and polythermal sections of the Ti-Al-Nb-Mo system are computed using the Thermo-Calc program, and temperatures of liquidus, solidus, and other phase transformations are found. It is shown that the general character of the microstructure after vacuum annealing and after HIP treatment at t = 1250℃ is approximately the same: eutectoid colonies γ+ α_2 and relatively compact particles of phases β and y. However, in contrast to vacuum annealing, HIP does not lead to the elimination of casting porosity. Data from metallographic analysis and electron probe microanalysis in general confirm the results of calculation.