Study of the Effect of Alloying and Hot Deformation on Properties of Small Stampings of Alloys Based on TiAl Intermetall
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STUDY OF THE EFFECT OF ALLOYING AND HOT DEFORMATION ON PROPERTIES OF SMALL STAMPINGS OF ALLOYS BASED ON TiAl INTERMETALLIC V. A. Duyunova,1 N. A. Nochovnaya,2 E. B. Alekseev,3 and V. I. Ivanov4
UDC 669.017.185
Intermetallic alloys based on TiAl compound are most promising high-temperature materials for gas turbine engines. The effect of alloying TiAl with active elements together with hot deformation and heat treatment on the structure of stamped components is studied. Alloy composition is selected and hot pressure treatment and heat treatment parameters are selected providing an improved set of mechanical properties in stamped components. Keywords: intermetallic TiAl alloys, alloying, hot pressure treatment, heat treatment, structure, mechanical properties.
In resolving problems connected with assimilation of hypersonic flight velocities requiring at elevated temperature good specific properties for elasticity, strength, oxidation resistance, etc., development and use of intermetallic materials is an important problem of contemporary materials science [1–4]. Success achieved in studying the Ti–Al composition diagram, a study of deformation mechanisms, correlation of the microstructure and mechanical properties of the intermetallic compounds observed, has made it possible to evaluate the prospective nature of alloys based on TiAl (gamma-alloys, in future γ -alloys) [5–10] compounds. Their use in aerospace engineering components leads primarily to a reduction in structural weight by 15–25% [11, 12]. It has been proposed to use gamma-alloys in gas turbine engine structures, although the level of ductility achieved for these alloys and increased specifications for reliability properties (fatigue strength, fracture toughness and impact loads) has limited their use in less loaded components such as low-pressure nozzle guide vanes [13-15]. The main difficulties preventing extensive assimilation of these alloys, connected with sensitivity towards testing, i.e., low temperature values of strength ( σ f ) and ductility ( δ ) in tension limited to values of ≈ 450–65 MPa and 0.5–2.5% respectively, and at the same time with compression the ultimate strength and relative elongation to failure reach values of σ f = 450–1400 MPa and ε = 45% [12]. Research has shown that it is possible to improve ductility by alloying, and also to change the microstructure that may be achieved by hot working and heat treatment. This provides the possibility of obtaining in alloys a stable phase composition with the optimum morphological structures [16–22]. A study has been made in this work of test composite alloys of the system Ti–48Al–2Me (at.%) in which as the “Me” vanadium, chromium, and niobium have been used. The aim of research is preparation in wrought workpieces in the form of disks mechanical property levels of 20 σ f > 550 MPa and δ 20 > 1%. FGUP All-Russia Scientific Research Institute of Aviation Materials (VIAM), Moscow, Russia. 1 E-mail: [email protected]. 2 3 4
E-mail: [email protected]. E-mail: а[email protected]
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