Reasons for good high-temperature tensile rupture property of high-W content (Nb,W) co-alloying TiAl-based alloy under low stress

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In order to explore why the high-W content TiAl-based alloy under low stress has better tensile rupture property, we still choose the vacuum-consumable-melted Ti-44Al-4Nb-1W-0.1B alloy. We carried out tensile rupture property testing at different time periods and different temperatures. The W content in (α2+γ) lamella matrix and microstructure before and after tensile rupture property testing are studied. At 800 °C, the B2 phase content gradually decreases and the W content in (α2+γ) lamella matrix gradually increases with the extension of time periods. For example, at 800 °C for 1370h, the B2 phase content has decreased from initial 12.024% to 1.188%. And, W content in matrix has increased from initial 0.88at.% to 1.07at.%. The tensile stress accelerates the radial diffusion of W atom. Importantly, EBSD analysis shows that, under low stress, there is no obvious stress concentration in the B2 phase region (≤800 °C), which avoids premature fracture, and makes B2 phase playing a good role in coordinating stress and strain, thus improving the tensile rupture property. However, at 900 °C, there is a slight stress concentration in the microstructure, leading to the formation of many holes, which is harmful to the tensile rupture property.