Low cycle fatigue of lamellar TiAl with 8.5 at.-%Nb was studied with a total strain amplitude of 0.28% at three temperatures: room temperature, 750°C and 900°C. At room temperature, the material exhibited cyclic hardening and the fracture mode was mainly interlamellar. At 750°C and 900°C, the material showed cyclic softening and the fracture mode was translamellar. The lattice strain in γ phase was almost tensile and larger tensile lattice strain in γ phase seems detrimental. Besides, the opposite direction of {201}γ and {100}α2 lead to crack propagation along α2/γ interfaces. B2/βo phase always suffered compressive lattice strain in the tests. The destruction of lamellar microstructure was the reason for colony refinement at 750°C and 900°C.

中文翻译：

---

高Nb含TiAl合金的循环变形及晶格应变分布

研究了含有 8.5 at.-%Nb 的层状 TiAl 的低周疲劳，在三个温度下的总应变幅度为 0.28%：室温、750°C 和 900°C。在室温下，材料表现出循环硬化，断裂模式以层间为主。在 750°C 和 900°C 下，材料表现出循环软化，断裂模式为跨层状。γ 相中的晶格应变几乎是拉伸的，γ 相中较大的拉伸晶格应变似乎是有害的。此外，{201}γ和{100}α2的相反方向导致裂纹沿α2/γ界面扩展。B2/βo 相在测试中总是受到压缩晶格应变。层状微观结构的破坏是在 750°C 和 900°C 时菌落细化的原因。