Transient Liquid Phase Diffusion Bonding Research Articles

Effect of bonding temperature on microstructure and properties of TLP joined Q355 steel with Cu interlayer

Abstract Q355 steel with Cu interlayer was bonded by transient liquid phase diffusion bonding (TLP-DB) at different bonding temperatures, and good bonding joints were obtained. The joints were characterized by optical microscopy, scanning electron microscopy and mechanical properties. The results show that there is a bending phenomenon caused by the difference of element diffusion at the bonding interface at the bonding temperature of 1050 °C. With the increase of the bonding temperature, the diffusion of Cu element plays a role in refining the grain, but with the increase of the bonding temperature, it will also lead to the overgrowth of the grain; At the bonding temperature of 1050 °C, there are obvious mutations in the diffusion of Cu and Fe elements, but the increase of the bonding temperature has a good effect on the interdiffusion of the elements. The mechanical properties test showed that with the increase of the bonding temperature, the hardness, shear strength, and impact toughness at the center of the joint increased first and then decreased, and all reached the maximum at 1100 °C. The electrochemical performance test showed that with the increase of temperature, the corrosion resistance of the joint also increased first and then decreased.

The Effects of Borides on the Mechanical Properties of TLPB Repaired Inconel 738 Superalloy

The transient liquid phase diffusion bonding (TLPB) method was used to repair an artificial crack in Inconel 738, which was notched by a femtosecond laser. Mixed ratios of BNi-1a:DF-4B were investigated at the bonding temperature of 1373 K (1100 °C) for 2 to 36 hours. The effect of borides on the mechanical properties of TLPB repaired joints was studied through analysis of the microstructure, fracture path, and morphology observations. The borides formation, morphology, distribution, and joints strength were studied in detail. The results showed that the diffusion of B can either increase or decrease the joint strength, depending on its distribution and morphology. The amount of large blocky Ni-B compounds in the precipitate zone were reduced with increasing holding time, which resulted in an increase in joint strength. Nevertheless, further increasing the holding time led to a decrease in joint strength because of the formation of continuous acicular borides in the diffusion-affected zone. The fracture modes of TLPB joints were also discussed on the basis of the microstructure and fractography.

A Review on Interlayer used Transient Liquid Phase Diffusion Bonding of Aluminium Matrix Composites

Solid state welding is a most appropriate welding process for joining aluminium matrix composites (AMCs). Diffusion bonding process, as a solid state welding process is proven that it exhibits better quality of joint strength. In transient liquid phase diffusion bonding (TLPB) process, interlayer plays a vital role in the microstructure of the joints which causes the mechanical properties of the joints. This review paper provides an overview of interlayer used by various authors to join AMCs by TLPB process.

Microstructure and Property of N5 Single Crystal Superalloy Joints Bonded by Transient Liquid Phase Diffusion Bonding

N5 single crystal was transient liquid phase (TLP) diffusion bonded under different conditions in vacuum environment using Ni-base insert metal. Scanning electron microscopy (SEM) was used to observe the microstructure of the joints. Results show that the typical TLP joint could be divided into rapidly solidified zone (RSZ), isothermally solidified zone (ISZ) and diffusion zone (DZ). The widths of RSZ decreases with the increase of holding time at any established bonding temperature, amount of bulk compounds decrease at the same time. Bonding temperature has a complex influence on TLP joint. High temperature creep rupture tests were performed, results reveal that the sample fractured in the joint interface and the fracture mechanism has been studied.

Transient liquid phase diffusion bonding for micro PCD tool fabrication

In this study, K30 (W 90 wt%, Co 10 wt%) and DX5 (W 84 wt%, Co 16 wt%) tungsten carbide were used as base metals for transient liquid-phase diffusion bonding (TLPDB). The filler metal was MBF20, a type of nickel alloy used to minimize the residual stresses that occur due to the differences in the expansion coefficients of the metals. MBF20 contained B, Si, and Cr, which reduced the melting point of the nickel alloy and enhanced its mechanical properties. The base metal and filler metal surfaces were cleaned by mechanical polishing and cleaning. Diffusion bonding was performed under vacuum at 1,000–1,500 K under low pressure than buckling load conditions. The microstructure on the localized bonded surface was analyzed using scanning electron microscope (SEM) and optical microscopy. Result of no significant change was observed in the diffusion bonding in the low-to-mid temperature range due to insufficient filler metal or base metal dissolution at the bonding site. However, at high temperatures, the filler completely melted and bonded to the base metal on both sides. Our results showed that temperatures approaching the recrystallization temperature were required to provide high-quality welds for ultra-precision joints and micro polycrystalline diamond (PCD) tool fabrication.

Corrosion Behavior of the Transient Liquid Phase Diffusion Bonding Joint of TiNi Shape Memory Alloy and Stainless Steel in Hanks' Solution

The transient liquid phase diffusion bonding (TLP-DB) was employed to join TiNi shape memory alloy (SMA) and stainless steel (SS) with an interlayer metal of Ag-Cu eutectic metal foil.The corrosion behavior of the TLP-DB joint in Hanks solution at 37°C was investigated by electrochemical methods.The results show that the corrosion resistance of the joint is comparable to, but lower than that of base metals during the early anodic polarization, and the corrosion rate of the joint is between that of TiNi SMA and SS in the transpassive region at high potentials. The corrosion resistance of the specimens in Hanks' solution is associated with the surface quality, mircotructure and the intermetallics. Both TiNi SMA and SS display the characteristics of localized corrosion with a little pitting corrosion, while the joints mainly show the characteristics of pitting corrosion concentrated on the enrichment Cu phases.

Transient liquid phase diffusion bonding Al-6061 using nano-dispersed Ni coatings

Transient liquid phase diffusion bonding (TLPDB) of Al-6061 containing 15 vol.% alumina particles was carried out at various bonding temperatures. A 5 μm thick electrodeposited Ni-coating containing 18 vol.% nano-size alumina particles was used at the interlayer. Joint formation was attributed to the solid-state diffusion of Ni into the Al-6061 alloy followed by eutectic formation and isothermal solidification at the joint interface. Examination of the joint region using scanning electron microscopy (SEM), wavelength dispersive spectroscopy (WDS) and X-ray diffraction (XRD) showed the formation of intermetallic phases such as Al 3Ni, Al 9FeNi and Ni 3Si within the joint zone. The results indicate that the incorporation of nano-size Al 2O 3 dispersions into the interlayer can be used to improve joint strength.

Transient Liquid Phase Diffusion Bonding of Steel Sandwich Panels under Small Plastic Deformation: Lab Experiment, Modeling, and Application

Plastic deformation was newly introduced in transient liquid phase (TLP) diffusion bonding of steel sandwich panels. The effect of plastic deformation on bonding strength was investigated through lab experiments. It was assumed that three factors, including newly generated metal surface area, deformation heat and lattice distortion all contribute to the acceleration of interface atoms diffusion and increase of diffusion coefficients. A numerical model of isothermal solidification time was developed for TLP bonding process under plastic deformation and applied to carbon steel sandwich panels bonding with copper interlayer. A reasonable isothermal solidification time was obtained when an effective diffusion coefficient was used. Based on lab experiments, the effects of plastic deformation on interlayer film thickness and isothermal solidification time were studied through theoretical calculation with the new model. The evolution of interlayer film thickness indicates a good agreement between the calculation and experimental measurement. The results show that the isothermal solidification time is obviously reduced due to the effect of plastic deformation. Furthermore, a new steel sandwich cooling panel for heat exchanger was fabricated by TLP diffusion bonding under 13.1% plastic deformation. The test results suggest that a steel sandwich panel of inequidistant fin structure can provide enhanced heat transfer efficiency.

Transient liquid-phase diffusion bonding of two-dimensional carbon–carbon composites to niobium alloy

Two-dimensional carbon–carbon composites (C/C) were successfully bonded to Nb alloy with a Ti/Cu interlayer by transient liquid-phase diffusion bonding (TLP-DB) in vacuum condition. The joining process consisted of two stages: solid diffusion bonding at 780 °C under joining pressure of 4 MPa for 30 min, and TLP-DB at 1050 °C for 30 min under 0 or 0.03 MPa. The results show that the eutectic Ti–Cu liquid, produced during the second stage, presented good wettability on the C/C surface and further infiltrated into the C/C matrix to take “nail effect”, hence the bonding mechanisms were deduced; however, the residual Cu layer that was intentionally preserved as a stress relief buffer effectively relaxed the thermal stress of the joint, both of which made contributions to promote the shear strength of the joint that reached as high as 28.6 MPa.

Effect of Heating Rate on Transient Liquid Phase Diffusion Bonding of Ni-Based Superalloy GTD-111

This study was carried out to investigate the effect of heating rate on dissolution and solidification behavior during transient liquid phase diffusion bonding of Ni-based superalloy GTD-111. The heating rate was varied by 0.1K/sec, 1K/sec, 10K/sec to the bonding temperatures 1373K and 1423K in vacuum. When the heating rate was slower and the bonding temperature was higher, the completion time of dissolution after reaching bonding temperature decreased. When the heating rate was very slow, the solidification proceeded before reaching bonding temperature and the time required for the completion of isothermal solidification was shorter. However, when the total time required for completion of solidification from the beginning of heating was considered, heating at 0.1K/sec was nearly the same as heating at 10K/sec.

Transient liquid phase bonding of a microduplex stainless steel using amorphous interlayers

Microduplex stainless steels are two phase alloys which show excellent corrosion resistance and toughness. In order to join these special steels, fusion welding processes are normally used and a second post-weld heat treatment is necessary to regain the original ferrite to austenite ratio. In this study, transient liquid phase diffusion bonding was used to join a 2205 duplex stainless steel with the aid of amorphous interlayers. The research compares a Ni–B–Si ternary system with that of an Fe–B–Si interlayer, and compositional, microstructural and mechanical assessment was used to determine the quality of the bonds produced. These preliminary results show that the nickel based interlayer stabilises the austenitic phase along the bond length, which hinders grain growth across the joint region. In contrast, the iron based interlayer produces diffusion bonds, which show microstructural and compositional homogeneity across the joint region. Furthermore, mechanical and pitting corrosion tests show that transient liquid phase diffusion bonds can achieve properties similar to those of the parent alloy.

Analytical Modelling of Solidification during Temperature Gradient TLP Diffusion Bonding

Imposing a temperature gradient when transient liquid phase (TLP) diffusion bonding is the basis of a new bonding method which has recently been developed in the Department of Materials Science and Metallurgy, University of Cambridge (UK Patent 9709167.2). The use of temperature gradient TLP diffusion bonding results in joints with excellent reliability and also shear strengths as high as those of the parent material (e.g. aluminium-based alloys and composites). Another feature of this new method is that diffusion of solute in the solid phase is not necessary for solidification to take place and therefore bonding times are significantly shorter than those in conventional TLP diffusion bonding (when there is no imposed temperature gradient across the liquid phase). A mathematical model is proposed in this paper which is capable of predicting bonding times and bond line displacements when TLP diffusion bonding under a temperature gradient. The bond line displacement and bonding time predicted by the model for an ideal Al-Cu binary system are compared with experimental results obtained using pure aluminium and copper. The theoretical values predicted by the model are in agreement with the experimental results.

Low Temperature Transient Liquid Phase (LTTLP) Bonding for Au/Cu and Cu/Cu Interconnections

The Low Temperature Transient Liquid Phase Diffusion Bonding (LTTLP) process has been used to reduce the residual stresses and hence, improve the thermal fatigue performance of bonds between dissimilar electronic packaging materials. Aluminum oxide plated with either gold or copper has been bonded to copper heatsinks at temperatures less than 160°C, using In-Sn eutectic solders. After two hours at the bonding temperature, Cu/In-Sn/Cu joints exhibit a remit temperature in excess of 470°C and provide static strengths up to four times greater than the original solder bonds. Au/In-Sn/Cu joints do not exhibit a high remit temperature due to the formation of a stable Au-In-Sn phase which melts below 130°C. Both types of joints exhibited acceptable thermal fatigue performance for the conditions which were studied.