以 Ti-44Al-3Mn-0.8(Mo,W)-0.1B-0.1C 合金(原子分数，%)为研究对象，经真空感应熔炼、轧制等工序制备出φ12 mm 棒材，通过设计不同热处理制度调控出近片层和等轴两种典型组织下的合金，采用 EPMA、SEM 和 XRD 等手段系统研究两种组织合金在 750 ℃热暴露不同时间后的表面组织演变， 并分析了热暴露前后两种组织合金的力学性能。 结果表明，两种组织结构短时热暴露(≤100 h)均在合金表面形成无明显分层的混合氧化膜；长时热暴露(≥200 h)氧化膜均增厚并分层。 近片层组织过渡层中存在大量 Laves 相，在靠近基体处的片层组织发生 α2+γ→γ+βo+Laves 退化现象，而等轴组织过渡层仅存在少量 Laves 相，靠近基体处组织更稳定。 拉伸性能测试表明，热暴露后表面组织的存在会引发室温脆断，高温下两类组织合金强度均下降，但塑性得到改善；当去除表面层后强度部分恢复，塑性略微降低。 对比两种组织的性能，经 500 h 热暴露后等轴组织力学性能更稳定，近片层组织因片层结构退化性能下降幅度更大。

Ti-44Al-3Mn-0.8(Mo,W)-0.1B-0.1C alloy (at.%) was investigated in this study, from which φ12 mm rods were prepared via vacuum induction melting and hot rolling. By employing different heat treatment regimes, two typical microstructures, near-lamellar and equiaxed, were obtained. The surface microstructural evolution of the two microstructure types after thermal exposure at 750 ℃ for various durations was systematically examined using EPMA, SEM, and XRD. The mechanical properties before and after thermal exposure were also analysed. The results indicate that after short-term thermal exposure (≤100 h), both microstructures develop a mixed oxide scale on the surface without obvious delamination. Upon long-term thermal exposure (≥200 h), the oxide scales thicken and delaminate. The transition layer in the near-lamellar structure contains a substantial amount of the Laves phase, accompanied by the degradation of α2+γ →γ + βo+Laves near the substrate. In contrast, the transition layer in the equiaxed structure shows only limited Laves phase formation and greater structural stability adjacent to the substrate. Tensile tests reveal that the presence of the surface oxide layer after thermal exposure induced brittle fracture at room temperature. While both microstructure types experience reduced strength at elevated temperatures, ductility is improved. After the surface oxide layer is removed, the strength is partially restored, although the ductility decreases slightly. A comparative assessment demonstrates that, following 500 h of thermal exposure, the equiaxed microstructure exhibitss more stable mechanical properties, whereas the near-lamellar structure experiences a more significant degradation in performance because of lamellar structure breakdown.