Berezos V. Theory and practice of production of titanium high-strength structural alloys ingots by the method of electron beam melting.

The doctoral dissertation is devoted to the solution of an important scientific and technical problem which consists in the development of the theory and practice of obtaining high-quality ingots of high-strength structural alloys based on titanium by the method of electron beam melting (EBM) with intermediate capacity. By the methods of mathematical modeling, the study of the thermal state of the ingot in the mold and the hydrodynamic processes that occur during the production of ingots of high-strength titanium alloys by EBM with intermediate capacity is conducted. For a quasi-established mode of continuous electron-beam melting, a three-dimensional mathematical model is developed, as well as the method of numerical calculation of related hydrodynamic and thermal processes in the crystallized metal during casting of titanium alloy from the intermediate capacity into a cylindrical bushing. Calculations are made within the framework of the constructed mathematical models and the influence of technological modes of EBM on the process of crystallization of titanium alloy ingots is determined. By solving a nonstationary thermal problem with a phase transition, the initial condition of which is the obtained temperature distribution in the ingot, the position of the shrinkage shell for the situation of instantaneous cessation of melt discharge into the mold and electron beam heating of the ingot end surface is calculated. The study of the peculiarities of evaporation of alloying components from ingots of high-strength complex-alloyed titanium alloys under vacuum and the action of electron beam heating is conducted. The technology of obtaining ingots of high-strength complexalloyed titanium alloys by the method of EBM with intermediate capacity was developed. The developed technology was tested on the example of obtaining new domestic highstrength complex alloyed titanium alloys T110 and T120, as well as industrial widely used (α + β) and pseudo-β titanium alloys (VT14, VT22, VT23, VT19). Recommendations for obtaining ingots of high-strength titanium alloys by the method of EBM with intermediate capacity are issued. Based on the calculations within the framework of the constructed mathematical models, the technology of obtaining ingots of economically alloyed titanium alloys by the EBM method is developed. A study of the quality of ingots, structure and mechanical properties of economically alloyed titanium alloys obtained by EBM, and it is showed that the method of EBM with intermediate capacity allows to obtain high-quality ingots in both chemical composition and structure. The technology of deformation and heat treatment of domestic high-strength alloy on the basis of titanium Т120 obtained by the technology of EBM with intermediate capacity is developed. The quality of semi-finished products from the domestic titanium alloy T110 and industrial high-strength complex alloyed titanium alloys VT14, VT22, VT23, VT19 obtained by the developed EBM technology has been investigated. Works on research of mechanical properties and structure of the received semi-finished products in the form of plates, rods and pipes from high-strength difficult-alloyed titanium alloys are carried out. The practical significance of the results of the doctoral dissertation is that a new advanced technology has been developed, the application of which for the production of domestic semi-finished alloys based on titanium will allow to waive the import of valuable foreign semi-finished products and expand their use by Ukrainian enterprises. In addition, the introduction of the developed EBM technology and obtaining with its help new alloys, doped mainly with cheap alloying elements, opens the possibility of creating the production of ingots of new promising economically alloyed high-strength titanium-based alloys in Ukraine.