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An important part in affecting the properties of the titanium alloy VT22 is a heat treatment (HT). Annealing of welded joints of the alloy also works as strengthening HT. Depending on the heating temperature, duration of annealing and the cooling rate, different combinations of strength and ductility could be obtained. Annealing is carried out in the VT22 alloy two-phase region (750 - 850 °C) followed by direct or stepwise cooling. This heat treatment results in a maximum heterogeneity of the structure with nearly an equal amount of α and β phases. It also provides a tensile strength of 1100 - 1300 MPa.

Electron beam casting technology is a unique method for obtaining cast products and semi-finished products from a wide range of titanium alloys. This technology can be very promissing in production of biocompatible titanium alloys for endoprosthesis. A particularly difficult and important task in this context is preparation of Ti-Zr-Nb-Sn system alloys with high strength and low modulus of elasticity. As a result of experimental development of specified alloys melt preparation technological modes, possibility of obtaining complex titanium alloys with a high content of zirconium and niobium was shown. It is also determined, that when the niobium content in the charge is more than 30 % wt. there is a decrease in the concentration of titanium and zirconium in the melt due to their freezing on the walls of the skull. As a result, there is a change in the chemical composition of the melt, the amount of niobium in which can exceed 50 % wt. Maximum amount of tin that can be assimilated in titanium-based melts under EBCT conditions is 5 % wt., and niobium-based melts are twice less. It has been proven that obtaining melts of Ti-Zr-Nb-Sn system with a precise chemical composition, using the chosen method, is a difficult and still unsolved problem, but due to the possibility of melting alloys with a high content of niobium and zirconium in its conditions, this method is effective in the production of master alloys and ingots for the production of powders used as raw materials for additive tmanufacturing. Keywords: titanium alloys for endoprosthesis, foundry production, Ti-Zr-Nb-Sn, electron-beam casting technology.

Modern approaches in the development of biocompatible titanium alloys with a high level of performance properties

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