High-Temperature Tensile Property of High-W-Content (Nb,W) Co-Alloying TiAl-Based Alloys under Different Tensile Rates

Abstract

To investigate whether high-W-content (Nb,W) co-alloying TiAl-based alloys have better high-temperature tensile property at different tensile rates, the Ti-44Al-4Nb-1W-0.1B alloy (high W) is designed and prepared. Meanwhile, the Ti-44Al-7.2Nb-0.2W-0.1B alloy (low W) and the Ti-44Al-8Nb-0.1B alloy (pure Nb) are also prepared for comparative analysis. The tensile property is tested at 800 °C. The microstructure evolution and fracture surface are studied. Finally, the two (Nb,W) co-alloying alloys exhibit higher ultimate tensile strength than the pure Nb alloying alloy at different tensile rates. The Ti-44Al-4Nb-1W-0.1B alloy shows higher ultimate tensile strength than the Ti-44Al-7.2Nb-0.2W-0.1B alloy at low tensile rate, but demonstrates lower ultimate tensile strength at high tensile rate. As W content increases, the alloy's grain size decreases, enhancing the fine-grain effect. Combined Nb and W elements also contribute to solid solution strengthening, while the B2 phase improves stress coordination. These factors lead to better dislocation strengthening, so that the ultimate tensile strength of the two (Nb,W) co-alloying alloys is higher than that of the pure Nb alloying alloy. Under different tensile rates, the three alloys exhibit a combination of trans-lamella fracture and trans-granular cleavage fracture modes.