Abstract
The effect of cast texture and aluminum content on the regularities of structure formation in the gamma+ alpha(2) titanium aluminide alloys during hot deformation at temperatures lower than the temperature of eutectoid transformation has been studied. The most important factors that promote brittle fracture of the gamma + alpha(2) alloys upon hot deformation and hinder the production of high-quality fine-grained semiproducts were found. New approaches to the selection of gamma + alpha(2) compositions and to their thermornechanical treatment were proposed. They include (a) the use of beta-solidifying gamma + alpha(2) alloys with boron microadditions and (b) two-stage deformation, including deformation, first, in the alpha + gamma phase field and, then, in the alpha(2) + gamma field, which ensures the most efficient refinement of the ingot structure, and (c) the use of a final heat treatment that provides the formation of a fully lamellar structure with well-controlled sizes of colonies and interlamellar spacings. These approaches allow one to simultaneously solve the problems of high plasticity required for many technological operations (sheet rolling and others) and high level of service characteristics after final heat treatment.
