Microstructural evolution and mechanical properties of the Ti₂AlNb Alloy with 3 wt.% W and 0.1 wt.% Y obtained using powder metallurgy technique 

Abstract

TiAl intermediate compound is an important material for high-temperature applications due to its superior creep resistance and oxidation resistance. It is suitable for high-pressure compressors and low-pressure turbine blades of advanced military aircraft engines. TiAl intermediate compound is an excellent substitute for nickel-based superalloys, as it can decrease weight by 40% and greatly enhance aircraft thrust-to-weight ratio. In this paper, the microstructure evolution and the mechanical properties of Ti₂AlNb alloy with a 3.0 wt.% W and 0.1 wt.% Y addition obtained by blending elemental ultrafine powders was investigated by XRD, SEM-EDS, and mechanical testing device. The findings show that high relative density of 0.9945, and the excellent mechanical properties of Ti₂AlNb–3W–0.1Y alloy can be obtained through isothermal sintering for 3 hour in a furnace with controllable argon atmosphere flow of 200 mL/min at 1,500 °C. The alloy’s tensile strength, yield strength, and elongation reach 1,030 MPa, 913 MPa, and 15.1% at 700 °C, respectively. Meanwhile, the 3 wt.% of element W is added to the alloy to form (TiW)C as the second strengthening phase, which is uniformly distributed in the matrix of Ti₂AlNb. The addition of Y element at 0.1 wt.% into the alloy can act as an effective scavenger of oxygen and inhibit the unsatisfactory precipitation of the brittle α₂-phase in the Ti₂AlNb alloy. Compared to the alloy without additives, the Ti₂AlNb alloy with 3 wt.% W and 0.1 wt.% Y demonstrated 13.5% and 19.35% improvements in the fracture resistance at 25 °C and 700 °C, respectively. The alloy’s yield strength was increased as well. The evolution regularity of the main metallography is (Ti₂AlNb–TiAl–Ti₃Al) → (Ti₂AlNb–Ti₃Al) → (Ti₂AlNb–Ti₃Al–(TiW) C) during the isothermal sintering of Ti–22Al–25Nb–3W–0.1Y alloy at 1,500 °C. This study provides technical guidance for the preparation of ultrafine TiAl-based alloy powder and high-temperature aerospace applications