Ni/TiAl composite brazed joints could significantly reduce the aircraft's weight. However, low interfacial adhesion, coarse and brittle-hard intermetallic compounds (IMCs) seriously limited the application of Ni/TiAl composite joints in the next generation of aerospace applications. So enhanced K4169/TiAl composite joints were investigated by vacuum brazed with (Ni53.33Cr20B16.67Si10/Zr25Ti18.75Ta12.5Ni25Cu18.75) composite filler metal (CFM) designed based on cluster-plus-glue-atom model. The shear strength of the joint reached 485 MPa, comparable to the 491 MPa of TiAl substrate. The flat and brittle-hard diffusion reaction layer between Zones I and II was eliminated, simultaneously generating CrB4 dispersion strengthening due to the CFM developed with the interfacial solid-liquid space-time hysteresis effect. In Zones II and III, IMCs all transformed into Niss(Cr,Fe)[0–88], Niss(Ti, Al)[004], and Niss(Zr,Si)[11–2] of circular and oval shapes through isothermal solidification. Meanwhile, the residual stresses and hardness were distributed in reticulated cladding characteristics. Thereby, lattice distortion led to solid solution strengthening and increased plastic toughness through crack termination and bridging mechanisms, which inhibited dislocations from plugging and crack propagation. Various interfaces in Zone Ⅳ were regulated into semi- and coherent interfaces. Ni3(Ti,Al)/(Ni,Ti,Al) and (Ni,Ti,Al)/AlNi2Ti were composed of higher interfacial bonding energy (2.771 J/m2, 2.547 J/m2) and Ni-Ni covalent bonds. Interfacial covalent bonding and large interfacial bonding energy coupling strengthened Zone IV. Consequently, cracks initiated at the (Ni,Ti,Al)[013]/Ti3Al[010] and expanded rapidly into TiAl substrate. Therefore, applying this method to design CFMs and regulate the phase, grain morphology, and interface's fine structure could provide new pathways for dissimilar hard-to-join metals.

中文翻译：

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分散体、固溶体和共价键耦合以增强 K4169/TiAl 复合钎焊接头的第一性原理和实验前景


Ni/TiAl 复合钎焊接头可以显著减轻飞机的重量。然而，低界面粘附力、粗脆性金属间化合物 （IMC） 严重限制了 Ni/TiAl 复合接头在下一代航空航天应用中的应用。因此，通过采用基于团簇加胶原子模型设计的 （Ni53.33Cr20B16.67Si10/Zr25Ti18.75Ta12.5Ni25Cu18.75） 复合填充金属 （CFM） 真空钎焊研究了增强的 K4169/TiAl 复合接头。接头的剪切强度达到 485 MPa，与 TiAl 基体的 491 MPa 相当。消除了 I 区和 II 区之间平坦而脆硬的扩散反应层，同时由于具有界面固液时滞效应的 CFM 而产生 CrB4 色散增强。在II区和III区，IMCs通过等温凝固全部转化为圆形和椭圆形的Niss（Cr，Fe）[0–88]、Niss（Ti， Al）[004]和Niss（Zr，Si）[11–2]。同时，残余应力和硬度分布在网状熔覆特性中。因此，晶格变形导致固溶体强化，并通过裂纹终止和桥接机制增加塑性韧性，从而抑制位错堵塞和裂纹扩展。区域 IV. 中的各种接口被调节为半相干接口和相干接口。Ni3（Ti，Al）/（Ni，Ti，Al） 和 （Ni，Ti，Al）/AlNi2Ti 由较高的界面键合能 （2.771 J/m2， 2.547 J/m2） 和 Ni-Ni 共价键组成。界面共价键和大界面键能量耦合强化了 IV 区。因此，裂纹始于 （Ni，Ti，Al）[013]/Ti3Al[010] 并迅速扩展到 TiAl 衬底中。 因此，应用这种方法来设计 CFM 并调控相、晶粒形态和界面的精细结构可以为不同的难以连接的金属提供新的途径。