Improvement of the mechanical characteristics of T110 alloy by optimizing its thermomechanical and heat treatment
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IMPROVEMENT OF THE MECHANICAL CHARACTERISTICS OF Т110 ALLOY BY OPTIMIZING ITS THERMOMECHANICAL AND HEAT TREATMENT P. E. Markovs’kyi1 and O. H. Molyar1, 2
UDC 669.295
We study the influence of thermomechanical treatment developed for two-phase α+β-titanium alloys on the microstructure and mechanical characteristics of a new Т110 titanium alloy. As a distinctive feature of the proposed method, we can mention the fact that, prior to hot deformation, the β -solution treatment is performed at a temperature of the single-phase β -region with subsequent cooling at a strictly controlled rate as a result of which it becomes possible to eliminate the negative influence of the initial coarse structure of the α-phase of cast material on the final microstructure and form in the alloy a homogeneous dispersed microstructure with the structure of phases similar to a globular structure in the course of subsequent plastic deformation at a temperature lower than the temperature of completion of the polymorphic transformation Tβ by 50–70°С. As a result, both the strength and plasticity characteristics increase substantially and simultaneously. The subsequent strengthening thermomechanical treatment with a somewhat elevated temperature of heating for hardening guarantees the increase in the strength up to the maximum high value (1366 MPa) attained for the standard (furnace) methods of heat treatment for sufficiently high levels of plasticity. The indicated balance of strength and plasticity is unique for titanium alloys treated by using the standard furnace methods of heating. Keywords: high-strength titanium alloys, strength and plasticity, thermomechanical and heat treatment.
Titanium-based alloys are unique structural materials for various branches of industry, including the aerospace engineering, where the requirements to the specific strength are especially strong [1, 2]. The strength of titanium alloys is determined not only by their chemical composition but also by the presence of some phases and microstructures formed, in turn, in different stages of production: from melting of the castings to the final heat treatment (HT) of finished products [2, 3]. As an important structure-forming factor, we can mention the thermomechanical treatment (TMT), which is completely responsible for the sizes of β -grains and crystallographic textures and, together with HT, determines the morphology and dispersity of the intragranular structures of these alloys. The resulting values of the mechanical and operating characteristics of titanium products also depend on some specific properties, in particular, on their weldability determined by the chemical composition of the alloys and fairly often insufficient to meet the requirements of designers [4]. Taking into account these requirements, the researchers of the Paton Institute of Electric Welding of the Ukrainian National Academy of Sciences and the ANTONOV State Enterprise developed a new Т110 titanium alloy (up to 6 wt.% Al, 3.5–4.8 Nb, 0.3–0.8 Zr, 1.5–2.5 Fe, 0.8–1.8 Mo, 0.8–2.0 V, balance Ti)
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