Reaction Layer Research Articles

Zirconia and Crofer Joint Made by Reactive Air Brazing Using the Silver Base Paste and Cu-Ti Coating Layer.

This study proposes a method to enhance the airtightness of the joint between the ZrO2 and Crofer alloy using coating technology. With the aid of vacuum sputtering technology, a titanium-copper alloy layer with a thickness between 1.5 μm and 6 μm was first deposited on the surface of ZrO2 and Crofer, respectively. The chemical composition of the deposited reaction layer was 70.2 Cu and 29.8 Ti in at%. Then, using silver as the base material in the reactive air brazing (RAB) process, we explore the use of this material design to improve the microstructure and reaction mechanism of the joint surface between ceramics and metal, compare the effects of different pretreatment thicknesses on the microstructure, and evaluate its effectiveness through air tightness tests. The results show that a coating of Cu-Ti alloy on the ZrO2 substrate can significantly improve bonding between the Ag filler and ZrO2. The Cu-Ti metallization layer on the ZrO2 substrate is beneficial to the RAB. After the brazing process, the coated Cu-Ti layers form suitable reaction interfaces between the filler, the metal, the filler, and the ceramic. In terms of coating layer thickness, the optimized 3 μm coated Cu-Ti alloy layer is achieved from the experiment. Melting and dissolving the Cu-Ti coated layer into the ZrO2 substrate results in a defect-free interface between the Ag-rich braze and the ZrO2. The air tightness test result shows no leakage under 2 psig at room temperature for 28 h. The pressure condition can still be maintained even under high-temperature conditions of 600 °C for 24 h.

High-temperature microstructure evolution and thermal stability of SiCf/Ti60 composites

The microstructure evolution and thermal stability of continuous SiC fiber-reinforced Ti60 (SiCf/Ti60) composites at elevated temperatures have not been reported. The objective of this study was to conduct thermal exposure experiments of SiCf/Ti60 composites at 400 °C / 100 h, 600 °C / 100 h, and 800 °C / 100 h. The aim was to compare the interfacial and matrix microstructures under hot isostatic pressure (HIP) conditions and to assess their thermal stability. The results show that SiCf/Ti60 composites have excellent long-term thermal stability at 600 °C thermal exposure, short-term thermal stability at 800 °C thermal exposure and the thickness of the reaction layer (RL) increases to ∼1.27 μm. From HIP to 800 °C thermal exposure, RL changes from fine-grained TiC ║ discontinuous silicides ║ coarse-grained TiC to fine-grained TiC ║ near-continuous silicides ║ medium-grained TiC ║ coarse-grained TiC. Large-sized β-Ti and S2 silicides precipitated in the matrix at 800 ℃ thermal exposure, where β-Ti and α-Ti followed the Burgers orientation relationship (BOR), and the S2 exhibited a multitude of orientation relationships with both β-Ti and α-Ti. Furthermore, it was demonstrated that thermal exposure resulted in a reduction in the dislocation density of the matrix. In particular, thermal exposure at 800 °C led to a decrease in the dislocation density of the matrix by ∼47 %. This observation provided a novel approach for the reduction of crystal defects in the matrix and the enhancement of the properties of SiCf/Ti composites.

Investigation of the erosion mechanism of fluorine-free mold flux on the submerged entry nozzle under the influence of negative electric field

Fluorine-free mold flux is receiving increasing attention due to the environmental and health problems associated with using fluorinated flux in casting. However, the erosion problem in the submerged entry nozzle is still exists and not solved. Therefore, in this study, the electric field is used to improve the erosion resistance capability of the nozzle. The results show that a thick protective adhesion layer is formed on the surface of the slag-line material under the action of a negative electric field due to an electrochemical reaction. This protective layer further reacts with the CaO/SiO2 content of the fluorine-free slag-line material to generate an interfacial reaction layer composed mainly of Ca2SiO4 and CaZrO3. Due to the presence of Ca2SiO4 in the interfacial reaction layer, a small amount of crystalline transformation occurs during the cooling process. Thus, under the protection of the double protective layer generated by the action of the negative electric field, the slag-line material is not subject to the erosion of the fluorine-free mold flux, and the erosion rate is only 0.37%.

Formation mechanism of TiC twin during densification of SiCf/Ti2AlNb composites

SiCf/Ti2AlNb composites were fabricated using the magnetron sputtering precursor wires method in conjunction with the hot isostatic pressing (HIP) technique. The morphology, elemental distribution, and structural characteristics of the interfacial reaction layer (RL) were examined through scanning electron microscopy (SEM), transmission electron microscopy (TEM), and wavelength dispersive spectroscopy (WDS). The results showed that the interface between SiC fibers and Ti2AlNb reacted to form TiC and α2. Due to the interdiffusion of elements at the interface, a small amount of Al atoms existed in the TiC layer. These Al atoms reduced the stacking fault energy (SFE) of TiC, which is beneficial for the formation and stability of Σ3{111} twin boundaries.

Improved slag resistance of ferrotitanium slag based Al2O3-SiC-C castables: The effect of reaction between SiC and TiO2

Ferrotitanium slag is a kind of waste slag produced by smelting ferrotitanium alloy. It has high refractoriness (>1790 ℃) and Al2O3 content (≥70 wt%), which can be used to replace bauxite to prepare Al2O3-SiC-C castables. However, excessive substitution will lead to the decrease of slag resistance of Al2O3-SiC-C castables because of impurities in the ferrotitanium slag. In this paper, the slag resistance of ferrotitanium slag based Al2O3-SiC-C castables was improved by increasing the SiC content. The results showed that the castables with 13 wt% SiC had good mechanical properties. Increasing the amount of SiC was beneficial to improve the slag resistance. SiC content increased from 5 wt% to 22 wt%, the erosion index of dynamic slag resistance decreased from 17.05 % to 11.18 %. During the dynamic slag resistance, the TiO2 in the ferrotitanium slag dissolved in the slag, then the SiC reacted with TiO2 in the slag to form TiC coating on the surface of SiC particles. SiC particles wrapped by TiC widely existed in the reaction layer, which prevented further erosion of the slag. Further, the reaction of SiC with TiO2 to consume TiO2 and generate SiO2 increased the viscosity of the slag in the reaction layer, thus hindering slag penetration.

Structure and property evolution of LaYbZr2O7/YSZ heterogeneous interface in double‐layer thermal barrier coatings after thermal exposure

AbstractDouble‐layer thermal barrier coatings are one of the development directions of thermal barrier coatings technology. LaYbZr2O7 (LYZO) has high toughness and low thermal conductivity, making it promising for use as a high‐temperature thermal barrier coating. However, its relatively poor mechanical properties, especially low fracture toughness, limit its further application. Therefore, we prepared a double‐layer coating of LYZO and Y2O3 partially stabilized ZrO2 (YSZ) using atmospheric plasma spraying, with the inner layer being YSZ and the outer layer being LYZO. The results showed that after spraying, LYZO was in the metastable fluorite phase, while YSZ was in the tetragonal phase. LYZO and YSZ had good chemical compatibility, and an interaction layer formed at the interface between them, with its thickness increasing with the sintering time. Eventually, after 100 h of heat treatment, the thickness reached 12 µm. The hardness of the LYZO/YSZ interface increased with the sintering time, reaching a maximum value after sintering at 1300°C for 10 h. When evaluating the interfacial bonding strength using indentation method, the length of cracks caused by indentation significantly decreased with the increase of sintering time. The increase in bonding strength can be attributed to the formation of a reaction layer and the reduction of thermal residual stresses. Raman spectroscopy was used to measure the thermal residual strain at the LYZO/YSZ interface. Unbalanced distribution of thermal residual stress and M phase was observed near the interface. As the sintering time increased, both thermal residual stress and M phase content decreased. In summary, the double‐layer thermal barrier coating of LYZO/YSZ has good potential for development.

In vitro and in vivo dissolution of biocompatible S59 glass scaffolds

Fabrication of porous tissue-engineering scaffolds from bioactive glasses (BAG) is complicated by the tendency of BAG compositions to crystallize in thermal treatments during scaffold manufacture. Here, experimental biocompatible glass S59 (SiO2 59.7 wt%, Na2O 25.5 wt%, CaO 11.0 wt%, P2O5 2.5 wt%, B2O3 1.3 wt%), known to be resistant to crystallization, was used in sintering of glass granules (300–500 µm) into porous scaffolds. The dissolution behavior of the scaffolds was then studied in vivo in rabbit femurs and under continuous flow conditions in vitro (14 days in vitro/56 days in vivo). The scaffolds were osteoconductive in vivo, as bone could grow into the scaffold structure. Still, the scaffolds could not induce sufficiently rapid bone ingrowth to replace the strength lost due to dissolution. The scaffolds lost their structure and strength as the scaffold necks dissolved. In vitro, S59 dissolved congruently throughout the 14-day experiments, resulting in only a slight reaction layer formation. Manufacturing BAG scaffolds from S59 that retain their amorphous structure was thus possible. The relatively rapid and stable dissolution of the scaffold implies that the glass S59 may have the potential to be used in composite implants providing initial strength and stable, predictable release of ions over longer exposure times.Graphical

Acoustic cavitation-induced microstructure evolution in ultrasonically brazed Al/Cu joints using Zn-Al alloy fillers

Tailoring the phase constitutions of the interfacial reaction layers under the assistance of ultrasonic vibration is a convenient method to fabricate high-strength Al/Cu brazing joints. In this study, 1060-Al and T2-Cu dissimilar metals were ultrasonically brazed with Zn-3Al (wt. %) filler metals. Effects of ultrasonic brazing time on the microstructure and mechanical properties of joints were investigated. Results showed that the CuZn5 intermetallic compound (IMC) layer and Cu-based diffusion layer were created on the Cu substrate surface in the joint ultrasonically brazed at 400 ℃ for 2 s. However, the CuZn5 IMC layer was gradually transformed into a thin Al4.2Cu3.2Zn0.7 IMC layer by increasing the ultrasonic vibration time to 15 s. A well-matched coherent interface was formed between the Al4.2Cu3.2Zn0.7 ternary phase and the Cu-based diffusion layer. The phase transition of the Cu-side interfacial layer correlated closely with the acoustic cavitations induced super-saturation regions near the Cu substrate surface. The measured tensile strength of the Al/Zn-3Al/Cu joint ultrasonically brazed for 15 s was 89.3 MPa, which was approximately 2.5 times higher than that brazed for 2 s, and the tensile failure mainly occurred at the interface between the Al4.2Cu3.2Zn0.7 layer and the Cu-based diffusion layer.

Interface strengthening mechanism of TZM/Q235 joint by ultrasonic-assisted electron beam welding with high entropy alloy interlayer

The high-strength joints of TZM/CoCrFeNiMo0.2/Q235 were realized by ultrasonic-assisted electron beam welding. The effects of ultrasonic vibration on the microstructure evolution and mechanical properties of the reaction layers were analyzed. A reaction layer with a thickness of >10 μm was observed at the TZM side region. The reaction layer was characterized by columnar Fe2Mo phases growing perpendicular to the fusion line and FCC solid solutions with different grain orientations. Under the action of ultrasonic vibration, the eutectic structure of Fe2Mo phases and FCC solid solutions was evenly distributed in the reaction layer, and the grain orientation of the FCC solid solutions in the reaction layer changed to be the same as that in the fusion zone. Compared with the joint without ultrasonic vibration, the difference of nanoindentation hardness between the Fe2Mo phases and FCC solid solutions and the residual stress inside the reaction layer of the welding joint with an ultrasonic power of 80 W were significantly reduced. The maximum tensile strength of the joints was 318.4 ± 26 MPa, which was 18.9% higher than that of the joint without ultrasonic vibration.

Effect of NiMo diffusion barrier plating preparation on microstructure and properties of Bi2Te3/Cu joints

Bismuth telluride (Bi2Te3) thermoelectric devices play a significant role in recovering low-grade waste heat. While for Bi2Te3/Cu joints, excessive interfacial reaction and diffusion usually happens, which greatly degrades their properties. In this work, the novel NiMo diffusion barrier plating was prepared on Bi2Te2.7Se0.3 (n-BST) surface prior to the soldering process. The joint interfacial microstructure, shear strength, contact resistance and thermal stability were systematically investigated. The maximum shear strength increased from 7 MPa to 12 MPa with the joint contact resistance decreasing from 11.86 μΩ⋅cm2 to 3.27 μΩ⋅cm2 after NiMo plating preparation. These n-BST/Cu joints were then annealed for different durations to investigate the joint thermal stability. After annealing at 110 °C for 250 h, a thin BiTe + NiTe2 reaction layer formed instead of the initial SnTe reaction layer. The joint shear strength maintained 9 MPa (less than 2 MPa without NiMo plating) and the joint contact resistance was only 12.39 μΩ⋅cm2 (249.89 μΩ⋅cm2 without NiMo plating). This work indicates that NiMo plating is an effective elemental diffusion barrier for n-BST/Cu joints.

Effect of material flow behavior on the formation of interfacial reaction layers and fatigue performance of dissimilar friction stir welded S45C and AA6061-T6

Effect of material flow behavior on the formation of interfacial reaction layers and fatigue performance of dissimilar friction stir welded S45C and AA6061-T6

Microstructure evolution of interface and matrix during the preparation of SiCf/Ti60 composites

In this paper, continuous SiC fiber-reinforced Ti60 (SiCf/Ti60) composites were fabricated by preparing SiCf/Ti60 precursor wires from matrix-coated fibers and hot isostatic pressing (HIP) consolidation. The microstructures of the precursor wires and composites were investigated using XRD, SEM, EPMA, EBSD, and TEM, which led to the microstructure evolution of the composites. The conclusions of this study are as follows. 1. A reaction layer (RL) with a thickness of approximately 0.1 μm already exists at the interface of the precursor wires during the preparation. The HIP process accelerates the diffusion of the carbon coating with the Ti60 matrix, resulting in an increase in the thickness of the RL to approximately 0.5 μm. This layer is primarily composed of fine-grained TiC layer || discontinuous silicides || coarse-grained TiC layer. 2. The matrix of SiCf/Ti60 precursor wires contains α-Ti (∼ 1.9 μm), S2 (∼ 50 nm), and β-Ti (∼ 50 nm), in the matrix, β-Ti is precipitated from α-Ti, and HIP makes α-Ti, S2, and β-Ti grow to ∼ 2.4 μm, ∼ 200 nm, and ∼ 300 nm, respectively. 3. There are 〈0001〉//axial direction (AD) and 〈10−10〉//AD fiber textures in the matrix of the precursor wires, and HIP makes the matrix undergo a plastic deformation dominated by dislocation slip, and the pole density of the two kinds of textures are both increased.

Microstructure and mechanical properties of Al2O3 ceramic and copper joints brazed with AgCuInTi brazing alloy

AbstractReliable metallurgical bonding between Al2O3 ceramic and copper was achieved by vacuum brazing using Ag–23Cu–14.5In–3.3Ti (wt.%) alloy. The representative interfacial structure of the joint was Al2O3/Ti3(Cu,Al)3O + γ‐TiO/Ag‐based solid solution + (Cu,Ag)7In3 + Ag–Cu eutectic + Cu‐based solid solution/copper. The interface microstructure evolved with process parameters, including the formation of γ‐TiO and Ti3(Cu,Al)3O, as evidenced by microstructural analysis and etched surface morphology. The relationship between fracture path and shear strength was established by observing the fracture morphology and performing shear strength tests on joints with various process parameters, utilizing the degree of the Ag‐based solid solution loss and the thickness of the reaction layer as evaluative factors. When brazed at 760 or 780°C for 20 min using a 100 µm brazing alloy foil, the brazed joints demonstrated a peak shear strength of 215 ± 25 MPa, and the fracture predominantly occurred in the Al2O3 matrix and Ti3(Cu,Al)3O layer.

Calcium‐ferrum‐alumina‐silicate (CFAS) corrosion behavior of Lu4Hf3O12 ceramics at 1400°C

AbstractIn this work, the corrosion behavior of rare‐earth Lu4Hf3O12 ceramic when exposed to a CaO‐FeO1.5‐AlO1.5‐SiO2 (CFAS) environment at a temperature of 1400°C was investigated, with a focus on exploring the associated phase transformation, microstructure evolution, and corrosion reaction mechanism. Results reveal that during the corrosion process, the CFAS melt infiltrates Lu4Hf3O12 particles through cracks, resulting in the formation of a continuous reaction layer. This reaction leads to the generation of several high‐melting‐point garnets, including HfO2, Lu3Al5O12, Ca3Fe2(SiO4)3 (Ca‐Fe garnet), and Ca3Al2Si3O12 (Grossular). These garnets effectively fill the voids within the Lu4Hf3O12 ceramics, preventing further infiltration of the CFAS melts. As time progresses, the rate of the reaction gradually increases, while the rate of infiltration consistently decreases. Consequently, a relatively stable corrosion layer is achieved, effectively impeding further corrosion.

Correlative characterization of plasma etching resistance of various aluminum garnets

AbstractPlasma etching is a crucial step in semiconductor manufacturing. High cleanliness and wafer‐to‐wafer reproducibility in the etching chamber are essential in order to successfully achieve nanometer‐sized integrated functions on the wafer. The trend toward the application of more aggressive plasma compositions leads to higher demands on the plasma resistance of the materials used in the etching chamber. Due to its excellent etch resistance, yttrium aluminum garnet Y3Al5O12 (YAG) is starting to replace established materials like SiO2 or Al2O3 in this kind of application. In this study, reactive spark plasma sintering (SPS) was used to manufacture highly dense YAG ceramics from the respective oxides. In addition, yttrium was replaced with heavier lanthanoids (Er, Lu), intending to investigate the role of the A‐site cation in the garnet type structure on the plasma erosion behavior. The produced materials were exposed to fluorine‐based etching plasmas mimicking the conditions in the semiconductor manufacturing apparatus and the erosion behavior was characterized by atomic force microscopy (AFM), secondary ion mass spectrometry (SIMS), transmission electron microscopy (TEM), and profilometry. The induced chemical gradient in the samples is limited to a few nanometers below the surface, which makes its characterization challenging. For advanced analysis, we developed a correlative characterization method combining SIMS and scanning TEM (STEM)–energy‐dispersive spectroscopy (EDS) enabling us to examine the structural and chemical changes in the reaction layer locally resolved. In the case of lanthanoid aluminates, an altered reaction layer and reduced fluorine penetration compared to YAG were found. However, a correlation between the characteristics of the induced chemical gradient and the determined physical erosion rates was not evident.

Influence of tantalum addition on the microstructure and wear resistance properties of NiCuBSi/65WC composite coatings

Nickel-based tungsten carbide composite coatings are extensively utilized on various wear-resistant workpiece surfaces due to their exceptional properties, including high hardness and wear resistance. However, as the WC content increases, uneven structure and susceptibility to cracking of the coating during the forming process are enhanced, thereby impacting its service performance. To address these issues, NiCuBSi/65WC composite coatings with varying tantalum (Ta) contents were fabricated on 42CrMo steel substrates by laser cladding. The influence mechanism of Ta content on the microstructure and wear resistance of the coatings was investigated. The results demonstrate that the addition of tantalum promotes the formation of reinforcement phases such as TaC and W2C in the coating. Moreover, with increased Ta content, the edge of WC particle reaction layers in the coating gradually transforms from sawtooth to shorter rod-shaped morphology. Additionally, as the Ta content increases, the dissolution degree of WC particles rises, thereby facilitating the formation of TaC and W2C compound carbide. This leads to an enhancement in both the quantity and uniform distribution of carbide reinforced phases within the coating, resulting in an increase in average coating hardness from 482.4 HV0.2 to 580.1 HV0.2. When the Ta content reaches 7 wt% in particular, no cracks are observed on the coating surface, and a uniform distribution of carbides is achieved. The relative wear resistance of NiCuBSi/65WC coating with 7 wt% Ta is approximately 2.36 times higher than that without Ta.

Interfacial reaction mechanism between Y-containing DD5 alloy and Al2O3 ceramic during directional solidification process

This study systematically investigated the influence of varying yttrium(Y) additions on the interfacial reaction mechanism between the DD5 superalloy melt and Al2O3-based ceramic molds during directional solidification. The analysis revealed the formation of a complex multilayer reaction layer at the alloy-ceramic interface. The interfacial products changed from CaO·6Al2O3 to a mixture of various yttrium oxides after Y was added. As the reaction time increased, the sequence of interfacial reaction products observed on the surface of Y-containing alloys progressed as follows: Y2O3, Y4Al2O9, YAlO3, and ultimately Y3Al5O12. Increasing the Y additions promoted the formation of a reaction layer with a higher atomic percentage of Y. The interfacial reaction process between the DD5 superalloy and Al2O3-based ceramic molds involved ceramic decomposition and diffusion, Y element diffusion and displacement reactions, Al2O3 dissolution and further diffusion of the Al element. This process resulted in the formation of different yttrium-aluminum oxides and related to the bidirectional erosion of the Y2O3. These interfacial reactions significantly contributed to the consumption of Y element within the alloy.

Effect of Cu-Sn-Ti solder alloy on morphology, bonding interface, and mechanical properties of cBN grits

Cubic boron nitride (cBN) grits were joined with a Cu70-Sn20-Ti10 solder alloy powder at a temperature of 960 °C for 20 min under vacuum. The bonding morphology, macroscopically and microscopically, was analyzed, along with the interfacial reaction layer products and thickness of Cu-Sn-Ti/cBN grits. The research extensively characterized the surface morphology and attachment phase of cBN grits both before and after a reaction process. The analysis also included a detailed examination of the cBN grits' morphology. Moreover, the research performed a comparative evaluation of the compressive strength of cBN before and after the reaction, providing valuable insights into the effect of the reaction process on cBN's mechanical properties. The results indicate that the solder effectively wets the surface of the cBN grits, demonstrating good wettability. At the microscopic level,the reaction layer with a structural sequence of cBN-TiB2-TiB-TiN forms at the interface between the two materials. This reaction layer is approximately 5.65 μm thick and exhibits a chemical metallurgical combination. Moreover, the compressive strength of cBN remained unchanged before and after brazing.

Strong and tough 3D-(SiC–Si3N4)/Al co-continuous composite with enhanced interfaces

Materials with high specific strength and toughness are urgently needed in the fields of electronic packaging, armor, and aerospace. SiC/Al composites show good potential for these applications but the problem of mutual exclusion of strength and toughness still needs to be solved. Herein, we propose a new strategy to simultaneously enhance its strength and toughness from the perspective of structural optimization and interface enhancement. Inspired by the nacre structure, a 3D-(SiC–Si3N4)/Al co-continuous composite was prepared by freeze-casting combined with the pressure infiltration method. During the process, elongated Si3N4 grains were introduced into the ceramic framework to design the internal lamella wall structure and increase the contact area with the aluminum substrate. Moreover, a favorable interfacial bonding was designed between Si3N4 and Al to improve interface wettability. The reliable microstructure of porous 3D-(SiC–Si3N4) preform was tailored through the adjustment of initial solid loading and the α-Si3N4 component. The effects of initial solid loading and the α-Si3N4 component on the microstructure, interfacial wettability, and mechanical properties of the final composites were investigated. The results showed that the SiC–Si3N4/Al composites possess high flexural strength (769 MPa) and fracture toughness (15.1 MPa m1/2), which is superior to data reported in general literature. Numerous elongated β-Si3N4 grains are produced on the ceramic skeleton, forming an interlocking structure with the aluminum matrix, which increases the contact area with the aluminum substrate. A chemical reaction layer was formed at the interface of the composite, greatly improving the interfacial bonding strength. This work provides a promising design guideline for developing and optimizing high-strength and tough composite.

Effect of Ti content on microstructure and properties of Cu/AgCuTi/Al2O3 brazed joints

In this study, four groups of Ag-Cu-Ti brazing powder with different Ti contents of 2 wt%, 3 wt%, 3.75 wt% and 4 wt% were prepared by vacuum atomization, and then modulated into brazing pastes. Brazing between oxygen-free copper and alumina ceramics with the brazing pastes and the wettability experiments of the brazing pastes on alumina were done by vacuum brazing process at 880℃ for 30 min. Microstructures and wettability of both the braze alloy and joints were analyzed by scanning electron microscope, energy dispersive X-ray spectrometer and transmission electron microscope, and shear strength of the joints was tested by self-designed fixture. Based on thermodynamic calculation and kinetic analysis, the relationship between the products of the reactive layer and the change of Ti content was plotted to explore the reaction and wetting mechanism of AgCuTi braze alloy on alumina ceramics. The results show that the content of Ti in AgCuTi braze alloy is the main factor affecting the brazing performance and wettability of the braze alloy by affecting the products of AgCuTi/Al2O3 reaction layer. The reaction layer consists of TiO when the Ti content is 2 wt%, the reaction layer comprises of TiO and Ti3Cu3O when the Ti content is 3 wt%, the reaction layer is made up of Ti3O2 and Ti3Cu3O when the Ti content is 3.75 wt%, and the reaction layer consists entirely of Ti3Cu3O when the Ti content is 4.6 wt%. With the increase of the Ti content within the range of 2–4.6 wt%, the wettability of the braze alloy on the alumina ceramics improved, and the shear strength of the Cu/AgCuTi/Al2O3 joints increased.