Structure and properties of titanium-aluminum alloys doped with niobium and tantalum

Autor: Ya. I. Yevich, Yu. M. Podrezov, N.I. Tsyganenko, T. Ya. Velikanova, V.T. Witusiewicz, Ulrike Hecht, A.A. Bondar, M. V. Remez, V. M. Voblikov
Rok vydání: 2011
Předmět:
Zdroj: Powder Metallurgy and Metal Ceramics. 50:397-415
ISSN: 1573-9066
1068-1302
Popis: Ternary as-cast Ti55−x Nb x Al45, Ti53−x Nb x Al47, Ti55−x Ta x Al45, and Ti53−x Ta x Al47 alloys, where x = 0, 4, 8, and 12, and Ti45Nb8−x Ta x Al47 and Ti47Nb8−x Ta x Al45 quaternary alloys, where x = 2, 4, and 6, melted in a laboratory arc furnace from pure components (~99.9 wt.%) are studied by X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), differential thermal analysis (DTA), and compression testing. The alloys are found to consist mainly of a superfine lamellar structure of decomposition β → α → α + γ → α2 + γ and contain tiny islands of the γ phase and also the β phase at 12 at.% Nb or Ta. The CALPHAD approach is used to obtain a thermodynamic description of the Al − Nb − Ta − Ti system, which adequately reproduces the experimental data. The compression tests performed at room temperature show that the ternary alloys with 45 at.% Al are characterized by higher strength but lower plasticity than the alloys with 47 at.% Al. For the Ti46Nb8Al46 and Ti46Ta8Al46 alloys, high strength in the temperature range 20 – 800°C and a drop in plasticity to 2 – 4% at 200 – 600°C are revealed. Among the quaternary alloys examined, the best combination of strength and plasticity (σ02 = 1043 MPa, σult = 1612 MPa, epl = 12.4%) is exhibited by the Ti47Nb4Ta4Al45 alloy.
Databáze: OpenAIRE
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