Abstract The long-term creep behaviour of the cast Ti-44.4Al-8.1Ta (at.%) alloy with an initial γ-TiAl(L10)+α2-Ti3Al(D019) microstructure was investigated at 700 °C. The alloy shows a remarkable creep resistance. The minimum creep rate is measured to be as low as 1.47 × 10−10 s−1 and total deformation is only 2.5% after an interrupted 30000 h creep test at 200 MPa. The creep exposure affects the stability of the initial microstructure. The discontinuous precipitation leads to the formation of γ + τ(Ti3Al2Ta) type of microstructure along the lamellar colony and grain boundaries. The decomposition of the α2 phase results in the formation of τ and γ + α2 + L12 segments within the lamellae and cellular γ + α2 + L12 network within the coarse particles. The intensive formation and coalescence of the cavities along the grain boundaries leads to predominantly intergranual type of creep fracture at the applied stresses of 250 and 300 MPa.

中文翻译：

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铸造 TiAl-Ta 合金的长期蠕变行为

摘要 研究了具有初始 γ-TiAl(L10)+α2-Ti3Al(D019) 显微组织的铸造 Ti-44.4Al-8.1Ta (at.%) 合金在 700 °C 下的长期蠕变行为。该合金显示出显着的抗蠕变性。经测量，最小蠕变速率低至 1.47 × 10-10 s-1，在 200 MPa 下中断 30000 小时蠕变试验后，总变形仅为 2.5%。蠕变暴露影响初始微观结构的稳定性。不连续的析出导致沿层状菌落和晶界形成γ+τ(Ti3Al2Ta)型显微组织。α2 相的分解导致在薄片内形成 τ 和 γ + α2 + L12 链段，并在粗颗粒内形成细胞 γ + α2 + L12 网络。