Titanium aluminide (TiAl) alloys, known for their light weight and high specific strength, hold promising potential for aerospace applications. Recent studies have focused on improving their properties through composite strengthening. An in situ synthesized Ti₅Si₃-reinforced TiAl composite with excellent performance was successfully fabricated via a dual-wire electron beam-directed energy deposition (EB-DED) process. The microstructure of the as-deposited Ti₅Si₃/TiAl composite consisted of primary Ti₅Si₃ rods, eutectic Ti₅Si₃ needles, and lamellar TiAl+Ti₃Al structures. The phase transformation during the EB-DED process was L→Ti₅Si₃+L→Ti₅Si₃+(α+Ti₅Si₃)_Eutectic→Ti₅Si₃+(Ti₃Al+TiAl)_Eutectoid. The expanded Blackburn orientation relationships among the ternary phases emerged from the eutectic reaction of L→α+Ti₅Si₃ with an undercooling exceeding 136°C and the subsequent eutectoid reaction with ordering transformation and were expressed as $<11\overline{2}0{>}_{\mathrm{T}{\mathrm{i}}_3\text{Al}}$//$<10\overline{1}0{>}_{\mathrm{T}{\mathrm{i}}_5\mathrm{S}{\mathrm{i}}_3}$//${<1\overline{1}0]}_{\text{TiAl}}$ and ${\left\{0001\right\}}_{\mathrm{T}{\mathrm{i}}_3\text{Al}}$//${\left\{0001\right\}}_{\mathrm{T}{\mathrm{i}}_5\mathrm{S}{\mathrm{i}}_3}$//${\left\{111\right\}}_{\text{TiAl}}$. The Ti₅Si₃ phase had a greater hardness than did the lamellar structures and enhanced the mechanical properties of the matrix. The compressive yield strengths at room temperature and 750°C were 1221±51 and 1034±34 MPa, respectively, whereas the tensile yield strength was 347.4±12.7 MPa at 950°C, surpassing those of other TiAl alloys. The calculated strength with different strengthening mechanisms was 1056.4 MPa, and the greatest improvement in strength was attributed to the decreased interlamellar spacing. This work provides critical insight into the design of TiAl composites with superior mechanical properties and aids in understanding the microstructural evolution of as-deposited Ti₅Si₃/TiAl composites.

中文翻译：

---

电子束定向能量沉积原位合成的 Ti5Si3 增强 TiAl 复合材料的新型取向关系和力学性能


钛铝化物 （TiAl） 合金以其重量轻和高比强度而闻名，在航空航天应用中具有广阔的潜力。最近的研究集中在通过复合材料增强来改善其性能。通过双线电子束定向能量沉积 （EB-DED） 工艺成功制备了性能优异的原位合成的 Ti₅Si₃ 增强 TiAl 复合材料。沉积态 Ti₅Si₃/TiAl 复合材料的微观结构由初级 Ti₅Si₃ 棒、共晶 Ti₅Si₃ 针和层状 TiAl+Ti₃Al 结构组成。EB-DED 过程中的相变为 L→Ti₅Si₃+L→Ti₅Si₃+（α+Ti₅Si₃）_共晶→Ti₅Si₃+（Ti₃Al+TiAl）_共晶。 三元相之间的扩展布莱克本取向关系源于 L→α+Ti₅Si₃ 的共晶反应，过冷度超过 136°C，随后的共析反应有序相变，表示为 $<11\bar{2}0{>}_{\mathrm{T}{\mathrm{i}}_3\text{Al}}$$<10\bar{1}0{>}_{\mathrm{T}{\mathrm{i}}_5\mathrm{S}{\mathrm{i}}_3}$${<1\bar{1}0]}_{\text{TiAl}}$ and ${\left\{0001\right\}}_{\mathrm{T}{\mathrm{i}}_3\text{Al}}$${\left\{0001\right\}}_{\mathrm{T}{\mathrm{i}}_5\mathrm{S}{\mathrm{i}}_3}$${\left\{111\right\}}_{\text{TiAl}}$.Ti₅Si₃ 相的硬度高于层状结构，并增强了基体的机械性能。 室温和 750°C 下的压缩屈服强度分别为 1221±51 和 1034±34 MPa，而在 950°C 下的拉伸屈服强度为 347.4±12.7 MPa，超过了其他 TiAl 合金。不同加固机构的计算强度为 1056.4 MPa，强度的最大提高归因于层间间距的减小。这项工作为设计具有优异机械性能的 TiAl 复合材料提供了重要见解，并有助于理解沉积态 Ti₅Si₃/TiAl 复合材料的微观结构演变。