Advanced Processes for High-Strength Titanium Alloys

摘要

In first part of this project, double Electron Beam Melting (EBM) was investigated for melting of high-strength alpha + beta and beta titanium alloys. The following advantages, as compared to Vacuum Arc Remelting (VAR), are expected: - full dissolution of LDl due to higher temperature and longer times in melt condition; - essential elimination of HDl by means of intermediate bath' application; - employment of cheaper initial materials, such as sponge blocks; - improved chemical homogeneity of ingots due to introducing alloying elements directly into a melting zone; * improved microstructure due to better controlled solidification of liquid metal. The second part of the project is aimed at the development of a novel approach in processing of beta alloys, which comprises cold or warm deformation and rapid heat treatment. An attractive advantage of beta-titanium alloys consists in a high plasticity in solid-solution metastable beta phase condition, which allows rolling of rods, sheets, foils, and other products at ambient temperature or in low (alpha + beta) region. Application of rapid heating as the final solid solutionizing treatment is supposed to allow formation of extremely fine beta-grain microstructure ensuring a sufficient ductility even in a high-strength condition. Detailed investigations of phase and microstructural evolution at continuous heating of solid solution and subsequently cold or warm rolled beta phase will be performed in order to establish the practical application of novel RHT technology.