Solid State Diffusion Bonds Research Articles

Solid-State Diffusion Bonding of Aluminum to Copper for Bimetallic Anode Fabrication.

The diffusion-bonding technique has been utilized to join various Al alloys (AA1060, AA2024, AA3003) to Cu for bimetallic anode application. This process aims to achieve robust metallic continuity to facilitate electron transfer, while carefully managing the growth of the intermetallic layer at the bonding interface. This control preserves the active volume of aluminum and prevents excessive brittleness of the anode. Optimization efforts have focused on different pressures, surface treatments of parent materials, and bonding parameters (temperature 450-500 °C and time 5-60 min). The optimal conditions identified include low bonding pressures (8 MPa), surface treatment involving polishing followed by chemical cleaning of the surfaces to be bonded, and energetic bonding conditions tailored to each specific aluminum alloy. Preliminary electrochemical characterization via cyclic voltammetry (CV) tests has demonstrated high reversibility intercalation/deintercalation reactions for up to seven cycles. The presence of the different alloying elements appears to contribute significantly to maintaining the high intercalation/deintercalation reaction reversibility without considerable modification of the reaction potentials. This effect may be attributed to alloying elements effectively reducing the overall alloy volume expansion, potentially forming highly reversible ternary/quaternary active phases, and creating a porous reaction layer on the exposed aluminum surface. These factors along with the influence of the Cu parent material collectively reduce the stress during volume expansion, which is the responsible phenomenon of the anode degradation in common Al anodes.

Solid State Diffusion Bonding of Alumina with Aluminum Alloy

The objective of this work is to study the effect of time during the bonding process of alumina with an industrial aluminum 6060 alloy by the technique of solid-state welding at 600°C. Optical microscopy, scanning electron microscopy with energy dispersive spectroscopy, corrosion tests, and microhardness measurements were used as characterization techniques. The extended time during the bonding process had an effect on the microstructure of the interface and its mechanical properties. Oxygen diffusion was detected across the aluminum alloy/alumina interface. A recrystallization reaction developed on the aluminum side during the bonding process, which affected the aluminum alloy hardness values. By bonding metal to ceramic, it allows the use of ceramics in automotive engines to reduce weight, increase thrust-to-weight ratio and operating temperature, and improve working efficiency.

Experimental investigation of the mechanical properties and microstructures of Ti–6Al–4V solid-state diffusion bonding joint under high temperature conditions

The mechanical properties and related mechanisms of the Ti–6Al–4V alloy solid-state diffusion bonding (SSDB) joint under elevated temperature conditions have been experimentally investigated in this study. Tensile tests with temperatures (298 K–1173 K) and strain rates (0.001 s−1, 0.1 s−1) of the joint and base metal (BM) were carried out. The microstructural evolutions were characterised by optical microscope, scanning electron microscope combined with backscatter diffraction. The results show that the tensile strength and elongation of the joint are slightly lower than the BM at 298 K, which is attributed to the higher Schmid factor and unbonded areas of the joint. However, at elevated temperatures from 1023 to 1123 K, the tensile strength of the joint turns to be higher than the BM, while the elongation of the joint is much lower than the BM. Grains with relatively high Taylor factors cluster at the DB interface. The larger number fraction of high angle grain boundaries (HAGBs−88%) and a higher inclination of strain hardening at DB interface, cause a higher strength of the joint at high temperatures. No significant plasticity variation of the joint is revealed because of primitive remnant holes and new straight HAGBs at DB interface. While when the temperature further increases to 1173 K, the difference of properties between the joint and BM become negligible. Corresponding reasons are characterized as dynamic recrystallization occurs at the interface of the joint at 1173 K, which is 50 K higher than that of BM, and the interface is eliminated.

Solid-State Diffusion Bonding of Pseudo-α-Ti Alloy to Ti-Stabilized Stainless Steel: With and Without Interlayer

Solid-State Diffusion Bonding of Pseudo-α-Ti Alloy to Ti-Stabilized Stainless Steel: With and Without Interlayer

Effect of Post-Weld Heat Treatment on the Solid-State Diffusion Bonding of 6061 Aluminum Alloy

The precipitation-hardenable aluminum alloy 6061 (AA 6061) is favored for aerospace components and automotive parts. However, the tenacious oxide layer on the surface greatly limits the quality and applicability of joining AA 6061. In this study, the joining method of solid-state diffusion bonding was implemented for AA 6061 plates, and the effects of post-weld heat treatment (PWHT) on the joint interface were investigated. The bonding temperatures were within the range of 500–530 °C, and the time periods varied from 30 to 240 min under a static pressure of 5 MPa in a vacuum. The diffusion bonded specimens were subjected to T4- and T6-PWHT to improve the bonding quality. The interfacial microstructure of the joints was analyzed by scanning electron microscopy, and the mechanical properties were evaluated with shear tests. The experimental results showed that the shear strength of the diffusion bonded joint could reach around 71.2 MPa, which was highly dependent on bonding temperature and holding time, and T6-PWHT further enhanced it to over 100 MPa. The effects of PWHT on the diffusion bonded AA 6061 joint were investigated, and the fractography on the sheared surfaces indicated that PWHT-T6 played an important role in enhancing joint strength, which was consistent with the measured shear strength. The sequential PWHT for AA 6061 after diffusion bonding was proven to be feasible for bonding of AA 6061 parts, and the joint strength was sufficient for industrial needs.

Modeling void closure in solid-state diffusion bonding of TC4 alloy

An analytical model is developed in effort to characterize the closure of interface void in the joint fabricated using solid state diffusion bonding (SSDB). Based on considering the relationship between the micro-deformation of the contact surface asperities and the macro-deformation of the joint, the model firstly quantitatively predicates the contribution of macro-deformation of joint on the bonding ratio without assuming the interface void geometries before analyzing the mechanisms of plastic and creep deformation. Furthermore, cooperating with the mechanisms of surface and interface diffusion, the correlation between the void closure (i.e. bonding ratio) and bonding parameters is investigated by the model. The results demonstrate that in the early stage of SSDB process, the void closure is mainly resulted from the contributions of the both mechanisms of plastic and creep deformation. However, with bonding time increasing, the mechanisms of surface and interface diffusion gradually become the dominated driving forces until the void elimination. The efficiency and applicability of the analytical model are verified by experimental results of diffusion bonding of TC4 titanium alloy with specially fabricated bonding surface, which demonstrates that the model can successfully forecast the effect of joining parameters on the void closure (or bonding ratio) evolution.

Microstructure and mechanical properties in the solid-state diffusion bonding joints of Ni3Al based superalloy

Directional solidification (DS) of intermetallic compounds Ni3Al based superalloys were joined by solid-state diffusion bonding (SSDB) with the joining interface perpendicular to the solidified direction. The joining process was conducted with a 4 μm pure Ni interlayer at 1100 °C under 15 MPa for 2–7 h. The results showed that the microstructure characteristics of the SSDB joints, microvoids, tiny carbides, a higher volume fraction of γ′ phase and high angle grain boundaries (HAGB) formed in the interlayer region, were significantly different from that of the base metal (BM). The joint of the best mechanical property, strength of 926 MPa and elongation of 7.2%, was produced by the bonding time of 7 h owing to the decrease of the microvoids and the large carbides with the bonding time increasing. However, the relative (ratio between the joint and the BM) tensile strength of the joint was merely 90% due to the existence of high angle grain boundaries (HAGB) generated after the recrystallization of the interlayer. Moreover, because microvoids were not vanished completely and the strain mismatch caused by the structure of the interlayer region, the hard center region (higher volume fraction of γ′ phase) and soft interface region (lower volume fraction of γ′ phase), so the stress concentration were produced between the joint and the BM under the tensile load. Therefore, the relative elongation of the SSDB joint was only 57%.

Cr2+:ZnSe active media with complex profiles of internal doping

Cr2+:ZnSe polycrystalline active elements in the form of disks with one and two inner doped layers were fabricated by using solid-state diffusion bonding (SSDB) with subsequent hot isostatic pressing. A comparison of the generation properties of active elements with the same absorption and various profiles of internal doping was made using a scheme with a semi-confocal cavity and CW thulium fiber laser pumping. All test samples showed high thermal and optical resistance at a pump power density of up to 50 kW cm−2 in room-temperature experiments that indicates the promise of using SSDB technology in high-power mid-IR lasers. The samples with two layers of internal doping demonstrated 30% higher lasing slope efficiency, than samples with one doped layer. This difference is explained by more uniform heating of the active element which was caused by increasing the volume of the sample involved in the absorption of pumping radiation.

Room-temperature lasing on Fe2+:ZnSe with meniscus inner doped layer fabricated by solid-state diffusion bonding

An Fe2+:ZnSe laser on a polycrystalline active element with an inner doped layer in the form of a meniscus operating at room temperature was investigated. The active element was manufactured using the solid-state diffusion bonding (SSDB) technique. The billets, in the form of plano-concave and plano-convex ZnSe lenses with a radius of curvature of 200 mm, were subjected to diffusion bonding. Before bonding, zinc selenide was doped with Fe2+ ions by diffusion through spherical lens surfaces by the process of hot isostatic pressing (HIP). After the SSDB procedure, the prepared sample was subjected to an additional HIP treatment. An Fe2+:ZnSe polycrystal was pumped by an electric-discharge hydrogen fluoride (HF) laser. The use of the active element with an inner doped layer in the form of the meniscus permitted an increase in the pump spot diameter, at which there was not yet any reduction in laser output energy associated with the development of transverse parasitic oscillation. This increase was ~19% (compared to samples with a single flat doped layer). The output energy of 480 mJ was achieved at a total efficiency (with respect to absorbed energy) of 38% on the 20 mm diameter Fe2+:ZnSe sample with the meniscus inner doped layer.

Microstructure and Kinetics of Intermetallic Phase Formation during Solid State Diffusion Bonding in Bimetal Ti/Al

In this study, tri-layered Ti/Al composites were synthesized using hot press/roll bonding, and then the annealing treatment was executed in the temperature range of 550–650°C for 2, 4, and 6 h. Interfacial layers were characterized using scanning electron microscopes (SEM), energy dispersive spectrometer (EDS), and X-ray diffraction (XRD). The results of microstructural characterization for all annealing temperatures and times indicated that the Al3Ti compound is the only intermetallic compound observed in the diffusion layers. The Al3Ti growth obeyed linear kinetics and was characterized by an activation energy of 128.7 kJ mol–1. The results indicated that the dominant diffusing component was aluminum and the growth of the Al3Ti layer occurred mainly at Ti/Al3Ti interfaces.

Effect of Alloying Elements Gradient on Solid-State Diffusion Bonding between Aerospace Aluminum Alloys.

Three different bonding couples assembled by two commonly used aerospace aluminum alloys were bonded within the temperature range of 460–520 °C under 6 MPa for 60 min in vacuum atmosphere. The interface microstructure and alloying elements distribution of the bonded joints were determined by scanning electron microscope (SEM) and Energy Dispersive Spectroscope (EDS); the bond strength was evaluated by tensile-shear strength test. The results show the bond quality improved effectively as the bonding temperature increased. Compared with the 1420-1420 and 7B04-7B04 bonding couples, the 1420-7B04 couples obtained better interface integrity and higher bond strength, the highest shear strength for 1420-7B04 couple can be as high as 188 MPa when bonded at 520 °C. Special attention was focused on the 1420-7B04 couple, the diffusion coefficient of Mg at the original interface under different temperatures were investigated, the results show the diffusion coefficient increased obviously as the bonding temperature increased. A diffusion affected zone (DAZ) without continuous intermetallic phases formed due to the diffusion of alloying elements across the bonding interface. The combined action of temperature and alloying elements gradient resulted in the increase of alloying elements diffusion fluxes, which in turn promote the bonding quality through the accelerated shrinkage of interfacial voids.

Solid-State Diffusion Bonding of Titanium by Using Metal Salt Coated Aluminum Sheet

In this study, the effect of metal salt coating processing of aluminum surface on the bond strength of the solid-state diffusion bonded interface of titanium and aluminum has been investigated by SEM observation of the interfacial microstructures and fractured surfaces after tensile test. Aluminum surfaces were coated by boiling in 5% aqueous solution of NaOH for 90 s and 98% formic acid for 60 s. Bonding process was performed at a bonding temperature of 713 ~ 773 K under a load of 12 MPa (for a bonding time of 900 s). As a result of the metal salt coating processing, high strength joint can be achieved with lower bonding temperature compared with unmodified joints. From this study, it is found out that metal salt coating processing is effective at removing oxide film and substitution to metal salt on the aluminum bonding surface.

Inconel718と(Ti, Al)N薄膜の固相拡散接合

Inconel718と(Ti, Al)N薄膜の固相拡散接合

Diffusion bonding between ODS ferritic steel and F82H steel for fusion applications

Diffusion bonding techniques were employed to join high Cr oxide dispersion strengthened (ODS) ferritic steel (Fe–15Cr–2W–0.2Ti–0.35Y2O3) and F82H steel under uni-axial hydrostatic pressure using a high vacuum hot press, and the microstructure and mechanical properties of the joints were investigated. The dissimilar joints were bonded by solid-state diffusion bonding (SSDB) and liquid phase diffusion bonding (LPDB). After bonding process, heat treatments were conducted to utilize the phase transformation of F82H steel for recovering the martensitic structure. Tensile tests with miniaturized specimens were carried out to investigate and compare the bonding strengths of each joint. Microstructure was observed for the bonding interface, and fracture mode was investigated after the tensile tests. LPDB joint of interfacial F82H steel fully recovered to martensite phase by post-joining heat treatments, while SSDB joint had ferrite phases at the interface even after heat treatment, which is considered to be due to decarburization of F82H steel during the bonding process. Therefore it is considered that the insert material plays a role as diffusion barrier of carbon during LPDB process. Microstructure observations and tensile tests of the joints revealed that the LPDB joints possess suitable tensile properties which are comparable to that of F82H steel. This indicates that LPDB is more promising method to bond ODS-FS and F82H steel than SSDB.

タフピッチ銅の拡散接合における表面粗さと接触タイミングの影響

タフピッチ銅の拡散接合における表面粗さと接触タイミングの影響

Solid-state diffusion bonding of high-Cr ODS ferritic steel

Solid-state diffusion bonding (SSDB) was employed to join high-Cr oxide dispersion strengthened (ODS) ferritic steel (Fe–15Cr–2W–0.2Ti–0.35Y 2O 3) blocks under uniaxial hydrostatic pressure using a high-vacuum hot press, and the microstructure and mechanical properties of the joints were investigated. High-Cr ODS ferritic steels were successfully diffusion bonded at 1200 °C for 1 h, without precipitates and microvoids at the bonding interface or degradation in the base materials. Transmission electron microscopic observation revealed that the nano-oxide particles near the bonding interface were uniformly distributed in the matrix and that the chemical composition across the bonding interface was virtually constant. At room temperature, the joint had nearly the same tensile properties and exhibited anisotropic behavior similar to that of the base material. The tensile strength of the joint region at elevated temperatures is nearly the same as that of the base material, with necking behavior at several micrometers from the bonding interface. The total elongation of the joint region decreased slightly at 700 °C, with an exfoliation fracture surface at the bonding interface. Although a small ductile–brittle transition temperature shift was observed in the joints, the upper shelf energy was fully reserved in the case of joints with L–R bonding orientation, for which cracks did not propagate on the bonding interface. Therefore, it is concluded that SSDB can be potentially employed as a joining method for high-Cr ODS ferritic steel owing to the excellent mechanical properties of the joints.

Microstructure of SiC / TiAl Interface Formed by Solid-State Diffusion Bonding

The microstructure of the solid-state diffusion bonded interfaces of silicon carbide (SiC) and titanium aluminide (TiAl) were investigated. A 100-µm-thick Ti-48at%Al foil was inserted between two SiC specimens and then heat-treated in vacuum. The interfacial microstructure has been analyzed by scanning electron microscopy, electron probe microanalysis and X-ray diffractometry. Four layers of reaction products are formed at the interface by diffusion bonding: a layer of TiC adjacent to SiC followed by a diphase layer of TiC+Ti2AlC, a layer of Ti5Si3CX containing Ti2AlC particles and a layer of TiAl2. However, the TiAl2 layer is formed during cooling. The actual phase sequence at the bonding temperatures of 1573 K and 1673 K are described as SiC/TiC/(TiC+ Ti2AlC)/(Ti5Si3CX+Ti2AlC)/Ti1-XAl1+X/TiAl and SiC/TiC/(TiC+Ti2AlC)/(Ti5Si3CX+Ti2AlC)/Ti5Al11 /Ti1-XAl1+X/TiAl, respectively. The phase sequences are successfully expressed on the basis of the Ti-Al-Si-C quaternary chemical potential diagram.

308 超塑性二相ステンレス鋼と炭素鋼の固相接合について(機械材料・材料加工II)

308 超塑性二相ステンレス鋼と炭素鋼の固相接合について(機械材料・材料加工II)

Brazed joints in γ TiAl sheet: microstructure and properties

γ TiAl sheet offers the potential to replace nickel alloy and steel in some gas turbine applications, with weight savings of up to 40%. Whilst it is recognised that the joining of γ TiAl sheets is a key manufacturing technology for such applications, it is relatively poorly developed and characterised. For this reason, brazing has been studied as a potential route to produce high quality structural joints in γ TiAl sheets. The work reported here has used a Ti–Cu–Ni braze alloy at the joint interface. High strength brazed joints have been produced, with shear properties similar to solid state diffusion bonds in γ TiAl sheet. The range of bonding parameters used produced significant variations in the microstructure of the joints but despite this, the measured shear strengths remained similar. Exposure of the joints to a temperature of 700 °C for up to 1000 h, showed that there was a slight increase in the shear strength with exposure time. However, oxidation studies noted that the brazed joints exhibited significantly poorer oxidation resistance in comparison with the base sheet alloy. This poor oxidation performance was thought to be tolerable and capable of being overcome for aerospace applications.

Interfacial Microstructure of Silicon Carbide and Titanium Aluminide Joints Produced by Solid-State Diffusion Bonding

This paper describes the microstructure and the formation mechanism of solid-state diffusion bonded interfaces of silicon carbide (SiC) and titanium aluminide (TiAl). Two SiC specimens were diffusion bonded using a Ti-48 at%Al foil in vacuum. The interfacial microstructure has been investigated by means of scanning electron microscopy, electron probe microanalysis and X-ray diffraction. Four layers of reaction products are formed at the interface by diffusion bonding: a layer of TiC adjacent to SiC followed by a diphase layer of TiC+Ti2AlC, a layer of Ti5Si3CX containing Ti2AlC particles and a layer of TiAl2. However, the TiAl2 layer is formed during cooling. The actual phase sequence at the bonding temperatures of 1573 K and 1673 K are SiC/TiC/(TiC+Ti2AlC)/(Ti5Si3CX+Ti2AlC)/Ti1� XAl1þX/TiAl and SiC/TiC/(TiC+ Ti2AlC)/(Ti5Si3CX+Ti2AlC)/Ti5Al11/Ti1� XAl1þX/TiAl, respectively. Ti5Al11 and Ti1� XAl1þX rapidly transform to TiAl2 during cooling. The layers grow obeying the parabolic law. The growth rate of the reaction layers change sensitively depending on the bonding temperature.