微量Al含量的变化可极大地影响TiAl合金的凝固路径，进而影响其热变形时所处相区。本工作通过电弧熔炼设备制备了不同Al含量的Ti-(43~45)Al-4Nb-1Mo-0.2B合金 (原子分数，%，简称TNM合金)铸锭，并根据Al含量分别命名为43Al、44Al和45Al。随后，采用热包套轧制法制备了TNM合金板材，系统研究了Al含量对TNM合金轧制过程中显微组织演化及力学性能的影响。结果表明，不同Al含量的TNM合金在1250 ℃变形时处于不同的相区。在轧制温度保温1 h后，43Al合金主要以等轴α/α₂晶粒为主；44Al合金形成了特殊的核(α₂/γ片层团)壳(α/α₂晶粒)结构；而45Al合金主要以大尺寸α₂/γ片层团为主。轧制前初始组织状态影响了轧制过程中显微组织演化规律，也决定了最终板材的组织形貌。随着Al含量的增多，TNM合金轧板的显微组织由近片层转变为双态，最终转为近γ。此外，在43Al和45Al轧板中分别观察到新生α₂/γ片层团和残余α₂/γ片层团。44Al合金由于特殊的核壳结构，轧制后可以同时获得上述2种类型的α₂/γ片层团。TNM轧板的室温力学性能测试结果表明，随着Al含量的增加，TNM合金轧板的室温强度逐渐降低。43Al合金轧板由于新形成的片层组织而表现出最佳性能，而44Al和45Al合金轧板由于等轴γ晶粒增多、团聚、异常长大或残余片层团的存在等因素而快速断裂失效。

Slight variations in the Al content can considerably affect the solidification path of TiAl alloys. Consequently, these variations influence the location of phase regions during the hot deformation process of TiAl alloys. In this study, Ti-(43-45)Al-4Nb-1Mo-0.2B (TNM, atomic fraction, %) ingots were synthesized via arc melting and labeled as 43Al, 44Al, or 45Al depending on their Al contents. Subsequently, TNM sheets were fabricated via hot-pack rolling, and the influence of Al content on the microstructure evolution and mechanical properties of these sheets during the rolling process was systematically investigated.Results indicate that TNM alloys with different Al contents are located in different phase regions when deformed at 1250 ^oC. After preheating for 1 h, the 43Al alloy is mainly composed of equiaxed α/α₂ grains. In contrast, the 44Al alloy exhibits a unique core-shell-like structure with α₂/γ lamellar colonies in the core and α/α₂ grains surrounding it. Compared with the 44Al alloy, the 45Al alloy demonstrates a lamellar structure with larger α₂/γ lamellar colonies. Furthermore, the initial structure remarkably influences the microstructure evolution of TNM sheets during the rolling process and determines the final microstructure composition of these sheets. With increasing Al content, the microstructure of TNM sheets transitions from nearly lamellar to duplex, eventually tending toward a near-γ structure. Additionally, two types of α₂/γ lamellar colonies—newly formed and initially present—are observed in the 43Al and 45Al sheets, respectively. Owing to its unique core-shell-like structure, the 44Al sheet simultaneously contains both types of α₂/γ lamellar colonies. Furthermore, the mechanical properties of TNM sheets with different Al contents were tested at room temperature. Results show a gradual decrease in the tensile strength of TNM sheets with increasing Al content. The 43Al sheet exhibits the best performance, which is attributed to the presence of newly formed lamellar structures. Meanwhile, the 44Al and 45Al sheets develop fractures rapidly because of the increased, clustered, and abnormal growth of equiaxed γ grains or presence of residual α₂/γ lamellar colonies.