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In this study, the carbon fiber reinforced ZrB2-SiC composite ceramic was joined to Ti6Al4V alloy with Ag-Cu eutectic alloy filler at varied holding time and a fixed temperature of 800℃. Interface microstructure and shear strength of brazing joints were studied. The brazed ZSCf ceramics/AgCu/TC4 alloy is endowed with good metallurgical bondings. A typical interfacial structure of joints brazed for 10 min was found as ZSCf/TiC/Ti5Si3/Ag(s,s)/Cu(s,s) + TiC/TiCu/Ti2Cu/(TiC + TiCu)/TC4 alloy. Increase of holding time did not vary the precipitated phase of the joints but decreased thickness of the Ag(s, s) and Cu(s, s) reaction layer and gradually thickened the Ti-Cu reaction layer near the TC4 side. The formation process of reaction products was discussed in detail. The holding time substantially influenced shear strength of the joints. A maximum shear strength of 39 MPa was reached at a brazing time of 20 min.

Ti–6Al–4V (TC4) and Ti–6.5Al–3.5Mo–1.5Zr–0.3Si (TC11) joints were achieved via Ti–37.5Zr–15Ni–10Cu (wt%) filler metal when the brazing temperature was in the range from 950 °C (below β-transus) to 1040 °C (above β-transus) for 10–60 min. The role of brazing parameters in the microstructure evolution as well as mechanical properties of both base alloys and brazed joints was studied. The research analysis suggested that the typical interfacial microstructure was divided into five characteristic zones including reaction phases of α-Ti, β-Ti and (Ti, Zr)2CuNi. With the holding time prolonged, the sectionalized structure transformed into lamellar Widmanstätten structure in the brazing seam at the temperature of 950 °C, and the optimized shear strength reached 616 MPa at 950 °C for 60 min. Nevertheless, when increasing the brazing temperature to 1000 °C, the joint shear strength tended to be stable as the holding time exceeded 20 min due to the elemental homogenization, and the shear strength reached 627 MPa for the holding time of 20 min. Tensile test results showed that the mechanical properties of both TC4 and TC11 alloys were dramatically degraded at the heat treatment temperature of 1000 °C owning to the drastic grain coarsening and phase transition. Additionally, the plastic strain of TC4/TC11 joint brazed at 1000 °C for 20 min was 1.66%, while that of joint brazed at 950 °C for 60 min reached 2.01%. The variation in mechanical properties of base alloys as well as brazed joints under different thermal conditions revealed that the optimized temperature for brazing of titanium alloys was lower than β-transus with a long time. [ABSTRACT FROM AUTHOR]

In this study, a Cu foam was used as the interlayer to enhance the brazing strength of ZTA/TC4 joints. Scanning electron microscopy (SEM), energy disperse spectroscopy (EDS), X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the interfacial microstructure of the joints, which is determined to be ZTA ceramic/Ag(s,s)+Cu(s,s)/TiO + Ti 3 (Cu,Al) 3 O/Ti 2 Cu 3 /TiCu/Ti 2 Cu/α+β-Ti/TC4 alloy. The effects of brazing temperature and holding time on the microstructure and mechanical properties of the joints are investigated. With the increase of brazing temperature and the holding time, Ti-Cu intermetallic compound layers thickens and the brazing seam narrows. When the joints are brazed at 850 °C for 10 min, the shear strength of the joints reaches the maximum value of 84.5 MPa, displaying a 95% increase compared to the joints without the Cu foam interlayer. [ABSTRACT FROM AUTHOR]

Ti 3 SiC 2 ceramic and TC4 alloy were successfully joined by a contact-reactive brazing technique using a Ni interlayer. The results showed that liquid phase formed by the eutectic reaction between Ni interlayer and TC4 alloy, which further reacted with Ti 3 SiC 2 ceramic, and Ti 2 Ni, Ti 3 AlC, TiC, Ti 5 Si 3 C x and τ 3 formed in the brazing layer. The width of the brazing layer increased and the amount of Ti 2 Ni phase decreased with increased brazing temperature and holding time. When the temperature reached 1040 °C, micro-voids appeared nearby the TC4 substrate in the joint, leading to a low joint strength. The microstructure of the brazing layer and the brazing fillet shape changed with increasing Ni foil thickness. Cracks were observed in the Ti 3 SiC 2 substrate near the fillet when 60-μm and 120-μm Ni interlayers were used. The formation mechanism of the joints during the bonding process is discussed on the basis of the phase diagram and the microstructural evolution. The maximum shear strength of the Ti 3 SiC 2 /TC 4 brazed joints was 126 MPa, which was 69% of that of the Ti 3 SiC 2 substrate. The corresponding fracture occurred in the brazing layer and the Ti 3 SiC 2 substrate. [ABSTRACT FROM AUTHOR]

Here, a novel brazing interlayer of bicontinuous nanoporous copper (N P–Cu) lamina was produced by chemically dealloying a magnesium-copper (Mg–Cu) binary alloy and applied for brazing a C/C composite and TC4 alloy along with AgCuTi alloy brazing filler. SEM, EDS, XRD, XPS, TEM and SAED were used to characterize the differences in microstructure and phase distribution of the samples and compare with samples without an interlayer. Mechanical testing in the form of shear tests were conducted to evaluate the change in shear strength caused by the interlayer. The large specific area, uniform nano scale porosity and ligaments of the N P-Cu lamina interlayer induced the transformation of Ti–Cu compounds from their bulk agglomerates to dispersed fine particles and formed eutectic phases, which contributed to relieving the residual stress and enhancing the plasticity of the joint seam. This led to a shear strength increase of 185% as compared to samples without an interlayer. • N P-Cu lamina was prepared by chemically dealloying Mg–Cu binary alloy in 0.1 M HCl. • N P-Cu lamina was used for brazing C/C composite-TC4 alloy with Ag–Cu–Ti filler. • Fine Ti 2 Cu particles, instead of TiCu-wrapped Ti 2 Cu agglomerates, formed in the joint seam. • Eutectic phases of Ag (s,s) and Cu(s,s) emerged which enhanced the joint plasticity and relieved the residual stresses. • The N P-Cu interlayer comparatively increased the shear strength of the joint by 185%. [ABSTRACT FROM AUTHOR]

Residual stresses in ceramic-metal joints is the important factor for their reliable implementation in cutting-edge industries. Composite fillers is reported to be a promising approach to reduce the residual stresses. Until now, few experimental researches on the brazing of ZrO 2 ceramic and TC4 alloy using composite fillers have been reported. In this study, to release the residual stresses and improve the joints strength, novel WB reinforced Ag-Cu composite filler was fabricated to braze ZrO 2 ceramic and TC4 alloy. Scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM) were applied for the analysis of microstructure and phases structure in the joints. The TiB whiskers and W particles were in situ synthesized via the reaction between active Ti and WB particles, and randomly distributed in the brazing seam. The effect of brazing temperature and WB content on interfacial microstructure and mechanical strength in the brazed joints were investigated. When brazed at 870 °C for 10 min, favorable microstructure reinforced by TiB whiskers and W particles in the brazing seam was achieved with 7.5 wt% WB addition in composite filler. The maximum average shear strength of the joints was 83.2 MPa, which about 59.4% increase over the joints without WB addition. [ABSTRACT FROM AUTHOR]

Vacuum brazing of C/C composite to TC4 alloy was performed using nano-Al2O3strengthened AgCuTi composite filler. The microstructure and main properties of the composite filler were characterized. The typical interfacial microstructure of brazed joint is TC4/diffusion layer/Ti-Cu intermetallic layers/Ag(s,s) + Cu(s,s) + TiCu/TiC/C/C composite. The effects of brazing temperature and addition of nano-Al2O3 on microstructure of brazed joints were investigated by SEM, EDS, TEM and XRD. The diffusion layer, Ti-Cu intermetallic layers and TiC layer thicken with the increasing temperature while the thickness of brazing seam decreases. The TiCu phase in brazing seam excessively develops and almost replaces the Ag(s,s) and Cu(s,s) when brazing temperature reaches 920 °C. The addition of nano-Al2O3 improves the performance of brazed joints by inhibiting the growth of Ti-Cu layers adjacent to TC4 side and offering dispersive nucleation sites for TiCu phase in brazing seam. The joint brazed at 880 °C for 10 min exhibits the highest shear strength of 27.8 MPa. The fracture positions of brazed joints are also discussed in this paper. [ABSTRACT FROM AUTHOR]

Cf/LAS composites and TC4 alloy were brazed successfully by vacuum brazing using Ag-Cu-Ti active filler metal. The interfacial microstructure was characterized by a scanning electron microscope, energy dispersive spectrometer and X-ray diffraction. The effects of brazing temperature on the interfacial microstructure and joint properties were investigated in details. Various phases including TiC, TiSi2, Ti3Cu4, Cu (s,s), Ag (s,s), TiCu and Ti2Cu were formed in the brazed joints. Interfacial microstructure varies greatly with the increase of brazing temperature, while the amount of Ti2Cu reduced, but no new phase is generated. The optimal shear strength of the joint is 26.4 MPa when brazed at 890 °C for 10 min. Shear test indicated that the fracture of the brazed joints went through the TiSi2 + TiC layer close to the Cf/LAS composites interface. [ABSTRACT FROM AUTHOR]

Reliable brazing of ZrO 2 ceramic to TC4 alloy is crucial for the wide applications in aerospace industries and biomedical devices. However, the brazing mechanism of ZrO 2 ceramic has not been investigated systemically compared to Al 2 O 3 and Si 3 N 4 ceramics. The nature of the reaction products adjacent to ZrO 2 ceramic still remains somewhat elusive. In this study, ZrO 2 ceramic and TC4 alloy was successfully brazed with inactive AgCu filler metal. The interfacial microstructure of the joints was characterized by scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The effect of brazing temperature on the microstructure and mechanical properties of the joints were investigated in details. The results revealed that Cu 3 Ti 3 O+TiO layers were formed adjacent to ZrO 2 ceramic while Ti–Cu IMCs layers were formed at TC4 substrate. With increasing brazing temperature, the thickness of Cu 3 Ti 3 O+TiO layers and Ti–Cu IMCs layers increased obviously. The hardness and elastic modulus of reaction phases were characterized by nano-indentation to reveal the plastic deformability. The highest shear strength of 52.2 MPa was achieved when brazed at 870 °C for 10 min. [ABSTRACT FROM AUTHOR]

A novel particle reinforced AgCu composite filler (abbreviated as AgCu C filler) was developed by introducing nano-Si 3 N 4 particles and micron-Ti particles into AgCu powder filler. Reliable brazing of TC4 alloy to Si 3 N 4 ceramic was achieved by using the AgCu C filler. The interfacial microstructure of TC4/AgCu C /Si 3 N 4 brazed joint was TC4/Ti–Cu intermetallic layers/Ag based composite reinforced by fine particles/TiN + Ti 5 Si 3 layer/Si 3 N 4 . The addition of nano-Si 3 N 4 in AgCu C filler improved the interfacial microstructure by suppressing the growth of continuous Ti–Cu intermetallic layers adjacent to TC4 alloy and promoting the formation of Ag based composite reinforced by particle phases in brazing seam. The continuous Ti–Cu intermetallic layers thicken and the TiCu 2 particle phases coarsened gradually with an increasing brazing temperature. Brazing defects including micro-cracks and nano-Si 3 N 4 aggregation were generated at higher brazing temperature. The highest average shear strength of 73.9 MPa was achieved when brazed at 880 °C for 10 min, which was higher than that of joints brazed using AgCu filler alone (49.2 MPa). [ABSTRACT FROM AUTHOR]

Vacuum brazing of SiO2 glass ceramic and TC4 alloy using a commercially available TiZrNiCu foil was investigated. The interfacial microstructure and the fractures were examined with an optical microscope (OM) and an S-4700 scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS) and an electron probe X-ray microanalyzer (EPMA). The structure of joint interface was identified by XRD (JDX-3530M). Meanwhile, the fracture paths of the joints were comprehensively studied. The results show that processing parameters, especially the brazing temperature, have a significant effect on the microstructure and mechanical properties of joints. The typical interface structure is SiO2/Ti2O+Zr3Si2+Ti5Si3/(Ti,Zr)+Ti2O+TiZrNiCu/Ti(s.s)/TiZrNiCu+Ti(s.s)+Ti2(Cu,Ni)/TC4 from SiO2 glass ceramic to TC4 alloy side. Based on the mechanical property tests, the joints brazed at 880 °C for 5 min has the maximum shear strength of 23 MPa. [ABSTRACT FROM AUTHOR]

[Display omitted] • A pure Ni foil was designed for high-strength C f /C-TC4 joining. • The optimal bond strength received was 64.2 MPa for the C f /C-TC4 brazed joints. • A smooth CTE transition across the interface was created in the C f /C-TC4 joint. • Solid-state phase transformation depressed the residual stresses in the joint. The C f /C composite-TC4 alloy joint brazed using traditional AgCuTi- or TiZrNiCu-based interlayers generally exhibited unsatisfactory bonding strength due to large mismatch of coefficient of thermal expansion (CTE) among the bonded materials. In this work, a pure Ni foil was designed for high-strength C f /C-TC4 joining. The results show that liquid solidification produced the Zone 1 while solid-state phase transformation gave rise to the Zone 2 in the joint. The optimal joint bond strength received was 64.2 MPa, which was the highest reported for the C f /C-TC4 joints. The Ni-Ti eutectic reaction imported the Ti 2 Ni matrix into the braze seam, creating a smooth CTE transition across the interface. Additionally, incorporation of soft phases into rigid matrix coupled with phase transformation triggered stress relief contributed to such an excellent bond strength. [ABSTRACT FROM AUTHOR]