P.E. Markovsky

Microstructure, texture, and mechanical properties of electron-beam melted Ti-6Al-4V

Abstract The chemical homogeneity, microstructure, texture, and mechanical properties of Ti–6Al–4V ingots synthesized via electron-beam melting were established. Despite large aluminum losses during melting, very uniform compositions well within the specification for the alloy were obtained in both 200- and 400-mm diameter ingots. The local conditions of melting and solidification produced essentially texture-free as-cast material with a largely equiaxed beta grain structure. Following hot working via rolling at various temperatures, a wide range of microstructures and textures similar to those found in conventionally-processed Ti–6Al–4V was obtained. The resulting mechanical properties were comparable to or better than those found in Ti–6Al–4V synthesized via vacuum arc remelting.

Grain growth and texture evolution in Ti-6Al-4V during beta annealing under continuous heating conditions

Abstract The kinetics of beta grain growth during continuous heating for two texturally-different, but microstructurally-equivalent, lots of Ti–6Al–4V material were determined using a direct-resistance-heating technique. Heating rates of 0.42, 5, 10, and 50 K s−1 were utilized. After reaching the peak temperature, a special cooling procedure was utilized to avoid complete decomposition of the beta phase during cool-down and thus enable direct determination of its texture at the end of high-temperature annealing. It was found that beta grain growth is strongly affected by texture whose evolution can give rise to a behavior which is discontinuous in nature. As a result, dramatic differences in grain-growth behavior were noted in the two lots of material and were explained in terms of variations in beta texture evolution during heat treatment.

Formation of biomimetic hydroxyapatite coatings on the surface of titanium and Ti-containing alloys: Ti–6Al–4V and Ti–Zr–Nb

Abstract Metals and their alloys play an essential role as biomaterials in orthopedics applications which can assist in the repair or replacement of load-bearing bones that have become diseased or damaged. Titanium and its alloys are base materials of implant engineering because of its lightness and durability. By coating Ti or Ti-containing surfaces with hydroxyapatite (HA) we can provide higher biocompatibility of implants, according to HA ability, to form a direct biochemical bond with living tissues. A method of surface modification by creation of special functional groups on the titanium surface followed by formation of “self-assembled” HA layer is reported. According to that, the titanium surface was modified by OH, Si-OH, and COOH functional groups. By comparative investigation it was found that the closest to natural stoichiometric HA Ca/P ratio obtained on the samples was modified by carboxyl groups. HA formation on surfaces of COOH-modified vanadium-titanium (VT6) and Ti–Zr–Nb alloys were studied and an investigation into the effect of the thermal conditions on HA deposition from simulated body fluid (SBF) of different chemical composition (10×-SBF and Tas-SBF) is provided. The formation of an HA coating on the surface of titanium and Ti-containing alloys has been confirmed by XPS, FTIR spectroscopy, and XRD.

Application of Local Rapid Heat Treatment for Improvement of Microstructure and Mechanical Properties of Titanium Products

Local Rapid Heat Treatment (LRHT) based on induction-heating methods can be used to form unique location-specific microstructures and properties in commercial titanium alloys while maintaining the bulk of the material in an initial, non-heat-treated condition. The present work is focused on practical aspects of LRHT application for microstructure/ mechanical properties improvement of some parts made of commercial titanium alloys. It is shown, that LRHT application could improve mechanical properties of such complicated part like turbine engine compressor blades, and two made of Ti-6Al-4V and VT22 titanium alloys goods after repair with Electron Beam Physical Vapor Deposition as well as with Build-up Welding.

Evolution of microstructure, phase composition, and tensile properties of severely cold deformed titanium metastable β alloy in rapid continuous heating

Abstract Influence of severe cold deformation of titanium alloy Ti–1.5%Al–6.8%Mo–4.5%Fe in metastable β condition on the evolution of phase composition, microstructure, and tensile properties during continuous rapid heating was studied. As-deformed alloy was characterized by quasi-amorphous single-phase β condition with an abnormal temperature dependence of electric resistance that was normalized after 48 h exposure at room temperature as a result of isothermal ω phase precipitation. Subsequent rapid heating with a rate of 5 °C/s caused recovery and recrystallization. Tensile properties of the alloy after different treatments were determined and discussed.