Conferences

Structure and Properties of Titanium–Aluminum Alloys Doped with Niobium and Tantalum

 
V.T.Vitusevich,
 
U.Hecht,
 
M.V.Remez,
 
V.M.Voblikov,
     

I. M. Frantsevich Institute for Problems of Materials Science of the NAS of Ukraine, Krzhizhanovsky str., 3, Kyiv, 03142, Ukraine
Powder Metallurgy - Kiev: Frantsevich Institute for Problems of Materials Science NASU, 2011, #07/08
http://www.materials.kiev.ua/article/1434

Abstract

Ternary as-cast alloys Ті55-хNbхAl45, Ті53-хNbхAl47, Ті55-хТахAl45, and Ti53-хТахAl47, where х = 0, 4, 8, 12, and quaternary alloys Ti45Nb8-xТахAl47 and Ті47Nb8-xТахAl45, where х = = 2, 4, 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 superfine lamellar structure of decomposition β → α→ α + γ → α2 + γ; they all contain tiny islands of the γ-phase and also β-phase at the Nb or Ta content of 12 at.%. 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 ambient temperature show that the ternary alloys with 45 at.% Al are characterized by higher strength compared to the alloys with 47 at.% Al, but the former are inferior to the latter in plasticity. For the Ti46Nb8Al46 and Ti46Та8Al46 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 МПа, σp = 1612 МПа, εпл = 12,4%) is found for the Ті47Nb4Та4Al45 alloy.


AL-NB-TA-TI, CALPHAD, LAMELLAR STRUCTURE, PHASE EQUILIBRIA, PLASTICITY, STRENGTH, TIAL