Search

In our work, 0.5 mol.% TiO2 was added to Ag‐xCuO (x = 2, 4, 8 mol.%) fillers whose compositions at 1050°C were in the L2 single liquid phase region, the boundary of the miscible phase region, and the L1+L2 miscible phase region, respectively. The role of TiO2 was derived by comparing the quenching microstructure of the fillers on the Al2O3 ceramics and the effect on the interfacial microstructure and shear strength of the joints before and after the addition of TiO2. The results showed that the TiO2 would dissolve into the CuO‐rich L1 liquid phase of the filler, leading it to spread outside the molten droplet. When brazing with Ag‐4CuO‐0.5TiO2 filler, the CuO at the joint interface almost completely disappeared, and the shear strength of the joint was significantly reduced. In contrast, the joint strength showed a small increase when using Ag‐8CuO‐0.5TiO2 filler, as the excess CuO at the interface of the brazed joint was reduced. When the filler composition was in the L2 single liquid phase region, CuO was diffusely distributed throughout the molten droplet. TiO2 was hardly contacted with CuO and its addition had no significant effect on the interfacial microstructure and the shear strength of the joints. [ABSTRACT FROM AUTHOR]

Dissimilar materials brazing of Ti2AlNb alloy to GH99 superalloy is of great pragmatic importance in the aerospace field, especially the lightweight space aircraft components manufacturing. In this work, TiZrCuNi amorphous filler alloy was used as brazing filler, and experiments were carried out at different brazing temperatures and times to investigate the changes in interfacial structures and properties of the joints. The typical interfacial microstructure was Ti2AlNb alloy/B2/β/Ti2Ni (Al, Nb) + B2/β + (Ti, Zr)2(Ni, Cu) + (Ti, Zr)(Ni, Cu)/(Cr, Ni, Ti) solid solution + (Ni, Cr) solid solution/GH99 superalloy when being brazed at 1000 °C for 8 min. The interfacial microstructure of the joints was influenced by diffusion and reaction between the filler alloy and the parent metal. The prolongation of brazing process parameters accelerated the diffusion and reaction of the liquid brazing alloy into both parent metals, which eventually led to the aggregation of (Ti, Zr)2(Ni, Cu) brittle phase and increased thickness of Ti2Ni (Al, Nb) layer. According to fracture analyses, cracks began in the Ti2Ni (Al, Nb) phase and spread with it as well as the (Ti, Zr)2(Ni, Cu) phase. The joints that were brazed at 1000 °C for 8 min had a maximum shear strength of ~216.2 MPa. Furthermore, increasing the brazing temperature or extending the holding time decreased the shear strength due to the coarse Ti2Ni (Al, Nb) phase and the continuous (Ti, Zr)2(Ni, Cu) phase. [ABSTRACT FROM AUTHOR]

Realizing the joining of SiC ceramic to Al0.3CoCrFeNi high‐entropy alloy is a technical interest for aviation, aerospace, and nuclear energy industry. In this study, the reliable brazing of SiC and Al0.3CoCrFeNi high‐entropy alloy was realized by inactive AgCu filler, which lays the foundation for the following research on ceramic‐high‐entropy alloy dissimilar joining. The interfacial microstructure was characterized by a scanning electron microscope and transmission electron microscope in detail, and the influence of Al0.3CoCrFeNi dissolution on interfacial reactions was studied. The effect of brazing temperature on microstructure evolution and mechanical properties was discussed. The results indicated that elements Ni, Fe, Co, and Cr from Al0.3CoCrFeNi were crucial for the joint formation. (Ni, Fe, Co)2Si + graphite + Cr23C6/(Cr, Fe)23C6 + (Ni, Fe, Co)2Si formed adjacent to SiC and (Fe, Co, Cr, Ni)–Si silicide + Cu(s,s) + Cu–Ni–Al‐rich phase formed next to Al0.3CoCrFeNi. The reaction layers on SiC side thickened and the morphology of (Fe, Co, Cr, Ni)–Si‐ and Cu–Ni–Al‐rich phase experienced distinct changes with the increasing temperature. The highest strength of ∼32.2 MPa was obtained at 850°C for 10 min. [ABSTRACT FROM AUTHOR]