Transient Liquid Phase Diffusion Research Articles

Microstructure and mechanical properties of C/C composite| Ti3Al alloy joints prepared by transient liquid phase diffusion bonding using AgCuNiLi alloy as joining material

Ag-27.5Cu–1Ni-0.5Li foil was employed to realize transient liquid phase (TLP) diffusion bonding of C/C composite and Ti3Al alloy successfully. C/C composite|Ti3Al alloy joints without obvious defects were obtained under 870 °C, 10min due to sufficient element diffusion and reactions between the interlayer and parent materials. According to the analysis results of the interface structure and element distribution in joints, AgCuNiLi alloy can spread and fill the joint presenting good wettability and chemical compatibility with parent materials, as well as Ti can diffuse from Ti3Al alloy into interlayer and react with C in interfacial layer adjacent C/C composite to form reaction layer during the bonding process. As a result, the joints with gradational structure, i.e. C/C| TiC + C| Ag (s, s) |Ag (s, s) + Ti–Cu intermetallics | diffusion layer|Ti3Al can be formed, which can improve the mechanical properties of the joints effectively, and the average shear strength of the joints can reach 33.78 ± 2.84 MPa. The shear fracture surface mainly occurs in reaction layer adjacent C/C composite extending into interlayer and presents rugged morphology, which can attribute to the permeation of liquid phase in C/C composite and ragged interface.

Microstructure and Properties of 20G/316L Dissimilar Metal TLP Welded Joints

The amorphous Ni foil used as the intermediate layer, the 20 steel/316L dissimilar metal was connected by double temperature transient liquid phase diffusion (TLP) welding to obtain a good metallurgical joint. By metallographic microscope (OM), Scanning electron microscope (SEM), energy disperse spectrometer (EDS), X-ray diffraction (XRD) and universal testing machines, the interface formation, elemental diffusion and mechanical properties of joints at different welding temperature were studied. The results show that when the welding temperature is 1080°C, there are large holes in the joint, and the holes gradually disappear with the increase of the welding temperature. Ni elements in intermediate layer and 316L both participate in the formation of the diffusion and dissolution layer I and II, while Cr elements do not participate in the formation of the diffusion and dissolution layer I. The hardness at the center of the middle layer is basically the same as that of 316L, but with the increase of welding temperature, the hardness at the center decreases, and the anti-shear strength increases.

Microstructure and mechanical property of SiC whisker coating modified C/C composite/Ti2AlNb alloy dissimilar joints prepared by transient liquid phase diffusion bonding

SiC whisker coating was prepared on the surface of C/C composite successfully by CVD, and transient liquid phase (TLP) diffusion bonding was employed to realize the joining of SiC whisker coating modified C/C composite and Ti2AlNb alloy using Ti–Ni–Nb foils as interlayer. The microstructure, shear strength and fracture behavior were investigated by scanning electron microscopy (SEM) with energy dispersive X-ray spectrometer (EDS), X-ray diffraction (XRD) and universal testing machine. The results show that SiC has good compatibility with C/C composite, and gradient interface formed between SiC-modified C/C composite and Ti2AlNb alloy. When the bonding experiment was carried out under bonding temperature of 1040 °C and holding time of 30min with 5 MPa pressure in vacuum, the joints formed well and no obvious defects can be observed. The typical microstructure of joints is C/C composite/SiC + TiC/Ti–Ni compounds + Ti–Ni–Nb solid solutions/residual Nb/diffusion reaction layer/Ti2AlNb alloy. With the increasing of bonding temperature, the thickness of joining area increased due to sufficient element diffusion. However, when bonding temperature is elevated to 1060 °C, some defects such as cracks and slag inclusions exist in the interface layer between interlayer and Ti2AlNb. The joints with maximum average shear strength of 32.06 MPa are bonded at 1040 °C for 30min. C, SiC and TiC can be found on the fracture surface of joints bonded at 1040 °C which indicated that fracture occurred at the interface layer adjacent SiC layer.

A novel method for the fabrication of porous calcium hexaluminate (CA6) ceramics using pre-fired CaO/Al2O3 pellets as calcia source

Herein, porous calcium hexaluminate ceramics that contain pores exhibiting multiple morphologies were fabricated via in situ reaction sintering using α-Al2O3 powders and pre-fired CaO/Al2O3 pellets. The results indicated that the composition of the pre-fired CaO/Al2O3 pellets significantly affected the pore morphology, reaction-diffusion mechanisms, sintering behaviour and properties of the porous CA6 ceramics. For the specimens containing low CaO/Al2O3-ratio (0.37) pellets, the main reaction occurred by solid state diffusion, i.e. ion diffusion through the solid reactant phase, which resulted in a slow process and low CA6 formation rate at an elevated sintering temperature. With higher CaO/Al2O3-ratio (0.57) pellets, large-sized pores were observed because of transient liquid phase diffusion during the sintering process. The transient liquid phase diffusion effect increased the porosity of the porous ceramics and promoted the formation of a large number of plate-like CA6 grains in the walls of the pores, enhancing their mechanical properties and high-temperature performance. The porous CA6 ceramics containing high CaO/Al2O3-ratio (0.57) pellets sintered at 1700 °C exhibited high open porosity (55.88%), low thermal conductivity and excellent high-temperature performance.

Microstructure and mechanical properties of TC4/0Cr18Ni9 joint prepared by transient liquid phase diffusion bonding

Because of significant difference in physical and chemical properties, the welding of titanium alloy and stainless steel is difficult. In order to solve the problems, TC4/0Cr18Ni9 joints were prepared by transient liquid phase (TLP) diffusion bonding using CuZn alloy as interlayer, and the microstructure, mechanical properties and bonding mechanism were studied and discussed. According to the morphological observation of interfaces and fracture surfaces, characterization of phases, tests of shear performance and micro hardness by scanning electron microscopy (SEM) with energy dispersive x-ray spectrometer (EDS), x-ray diffraction (XRD), universal testing machine, vickers micro-hardness tester and so on, CuZn alloy has good wettability and compatibility with TC4 and 0Cr18Ni9 as a interlayer material. Gradient structural joints are formed by sufficient element diffusion and reactions during TLP diffusion bonding. Compared with the interface bonding area adjacent 0Cr18Ni9 side, the joining area adjacent TC4 side is more continuous and denser without obvious defect. Hardness gradually increases from 0Cr18Ni9 side to diffusion reaction layer adjacent TC4, and then slightly reduces form diffusion reaction layer to TC4. The shear strength of TC4/0Cr18Ni9 joint can reach 146.4 ± 5.0 MPa and the fracture is not completely brittle. Ti2Cu and FeZn13 can be detected on the fracture surface of TC4/0Cr18Ni9 joint, which indicates fracture is apt to take place in the interface region adjacent 0Cr18Ni9 side.

On the Role of Bonding Time on Microstructure and Mechanical Properties of TLP Bonded Al/Mg2Si Composite

Transient liquid phase diffusion bonding of an aluminum metal matrix composite with 15 wt.% Mg2Si reinforcement particles using Cu powder interlayer at 560 °C for different bonding times has been studied. Three different zones were identified at the bonding line: athermally solidified zone, isothermally solidified zone and base metal. By increasing the bonding time, due to the diffusion of copper to the substrate, the width of the athermally solidified zone decreased, became more homogenous and the amount of intermetallic phase (CuAl2) decreased. Therefore, the shear strength increased to a maximum of 60 MPa for the samples with a holding time of 5 h at the bonding temperature.

Joints Properties of Aluminum Foams/Aluminum Plate by Transient Liquid Phase Bonding Process

Aluminum foams/aluminum plate was transient liquid phase diffusion bonded with Cu/Al/Cu composite interlayer, then the investigation on joint microstructure, element diffusion and joint strength was conducted at 565°C. The results showed that, there was a significant grain boundary penetration phenomenon near the interface and it was more seriously at the side of aluminum foams. The XRD results showed indicated that the main phases near the interface were α-Al, CuAl2, AlCu, Al4Cu9, Al2O3. By EDS line scanning, it indicated that the diffusion behavior of elements was different at three regions, compared with the edge region, the interface of the central region was better and the depth of element diffusion is larger, at the pore region, the liquefaction of interlayer was not successfully and the morphology was lamellar. Mechanical properties test showed that the largest shear strength of joint was 4.61 MPa when the duration was 40 min. Key words: Aluminum foams; transient liquid phase bonding; microstructure; element diffusion; shear strength

Effect of T6 treatment on transient liquid phase diffusion bonded joint of A6061 by using formate coated zinc sheet

Effect of T6 treatment on transient liquid phase diffusion bonded joint of A6061 by using formate coated zinc sheet

A novel and green preparation of porous forsterite ceramics with excellent thermal isolation properties

This work provides a novel and green approach to preparing porous forsterite ceramics by a transient liquid phase diffusion process based on fused magnesia and quartz powders without detrimental additives. The size of quartz particles markedly affected the sintering behaviors, phase composition, microstructure and properties of the porous forsterite ceramics. Fine quartz particles (D50, 3.87 µm) accelerated the rate of the forsterite formation at elevated temperatures and promoted solid-state sintering behavior of the porous ceramics. Conversely, coarse quartz particles (D50, 25.38 µm) reduced the rate of the solid state reaction and a large amount of unreacted SiO2 and enstatite (MgSiO3) phases transformed into a transient liquid-phase during the firing process. This effect resulted in a high porosity (approximately 58.89%) and formation of many large pores (mean pore size of 42.36 µm). These features contributed to the excellent thermal isolation properties of the prepared porous forsterite ceramics. The strength of the obtained porous ceramics (about 23.6 MPa) is relatively high compared with those of conventional ceramics.

The preparation and mechanical properties of carbon/carbon (C/C) composite and carbon fiber reinforced silicon carbide (Cf/SiC) composite joint by partial transient liquid phase (PTLP) diffusion bonding process

Using Ti/Ni/Ti multiple foils as interlayer, carbon/carbon (C/C) composite was bonded to carbon fiber reinforced silicon carbide (Cf/SiC) composite by partial transient liquid phase (PTLP) diffusion bonding process. The multiple gradient structures, i.e. C/C composite | Ti-C reaction layer | Ni-Ti intermetallic compound | residual Ni foil | Ni-Ti intermetallic compound | Ti-C reaction layer | Cf/SiC composite, were formed during joining process. All the interfaces are bonded well, except for some micro-pores appeared in the interface between the residual Ni layer and Ni-Ti layer. The shear strength of the joint was 44.7 ± 12.8 MPa at room temperature. The X-ray result indicates that only diffraction peaks of C, TiCx and Ni-Ti Intermetallic compound were observed, while no diffraction peaks of Si were found on the fracture surface. Thus, it could be deduced that fracture occurred in the interfacial area adjacent to C/C composite side.

Transient liquid phase diffusion process for porous mullite ceramics with excellent mechanical properties

Porous mullite ceramics were fabricated by the transient liquid phase diffusion process, using quartz and fly-ash floating bead (FABA) particles and corundum fines as starting materials. The effects of sintering temperatures on the evolution of phase composition and microstructure, linear shrinkage, porosity and compressive strength of ceramics were investigated. It is found that a large amount of quartz and FABA particles can be transformed into SiO2-rich liquid phase during the sintering process, and the liquid phase is transient in the Al2O3-SiO2 system, which can accelerate the mullitization rate and promote the growth of mullite grains. A large number of closed pores in the mullite ceramics are formed due to the transient liquid phase diffusion at elevated temperatures. The porous mullite ceramics with high closed porosity (about 30%) and excellent compressive strength (maximum 105 MPa) have been obtained after fried at 1700 °C.

Microstructural evolution and mechanical properties in the partial transient liquid phase diffusion bonding of tungsten to steel

The paper describes the design and examination of Ti/Cu double interlayer to produce a joint between tungsten and steel. Partial transient liquid phase diffusion bonding was performed by a double stage bonding process. To join tungsten to steel, the brazing of steel to a Cu interlayer (500 μm) was carried out at 1050 °C followed by transient liquid phase diffusion bonding to tungsten using an active Ti interlayer (25 μm) at 1000 °C. Microstructural evolution was studied at different bonding times (5, 15, 30, 60 and 180 min) to reveal the diffusion behavior of Ti atom in the interfacial zone between W and Cu. With the increase of the bonding time, the inserted active Ti interlayer and the formed Ti–Cu base intermetallic phases tend to be molten and consumed by the formed liquid alloy in the W-steel joint, while the tensile strength of the joint increases. The strength of the bonded specimens is as high as 412 MPa at the bonding time of 180 min. This technique provides a reliable method of bonding W to steel.

Transient liquid phase bonding of copper and ceramic Al2O3 by Al/Ni nano multilayers

Transient liquid phase (TLP) diffusion bonding has been achieved for the dissimilar joining of ceramic Al2O3 and copper using Al/Ni multilayers as interlayers at low temperature. The freestanding Al/Ni nano-multilayers were deposited by direct current magnetron sputtering and their properties were studied by X-ray diffraction, differential scanning calorimetry and scanning electron microscopy (SEM). The joining experiments were carried out at 550, 650 and 750°C for a holding time of 30min without extra pressure under nitrogen protection. The interfacial microstructure and microstructural characterization of the diffusion welded joints were investigated by SEM, energy dispersive X-ray spectroscopy and element mapping. The effectiveness of different temperatures for the mechanical properties of the joints was evaluated by shear strength. In the present work, an AuSn solder was added to expand the surface contact of the welding. The results show that the applications of Ni/Al multilayers and the AuSn solder reduce the bonding temperature and improve the joining quality.

Microstructural evolution and properties of TLP diffusion bonding super-Ni/NiCr laminated composite to Ti-6Al-4V alloy with Cu interlayer

Transient liquid phase (TLP) diffusion bonding super-Ni/NiCr laminated composite to Ti-6Al-4V alloy was performed at 950°C with the pressure of 5MPa. Two configurations (super-Ni/Cu/Ti-6Al-4V and Ni80Cr20/Cu/Ti-6Al-4V) were designed to explore interfacial microstructure evolution and mechanical properties. Results showed that the joint of laminated composite and Ti-6Al-4V alloy was mainly divided into two diffusion layers and a reaction layer. The interface was composed of Ni(Cu), Cu(Ni), Ti2Cu, TiCu, Ti3Cu4, Ti2Cu3 and Ti-Cu eutectic microstructure. The width of each layer increased with prolonging the bonding time and the growth rate of interfacial layers was dominated by the diffusion rate of alloying elements i.e. Cu, Ni and Ti. The maximum value of shear strength for both two configurations was about 58MPa.

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.

Liquid Phase Diffusion Bonding of AC2C/ADC12 Aluminum Casting Alloy by Using Metal Salt Coated Zn Sheet

Currently, the common way of bonding aluminum together is brazing. However, brazing creates problem when the high brazing temperature causes the formation of brittle intermetallic compound in between the joints prompting the need to circumvent this difficulty by considering transient liquid phase diffusion bonding method as a possible alternative. Being considered as a possible alternative solution, transient liquid phase diffusion bonding is not without problems that need to be overcome. One of these problems is the presence of oxide film on the insert material surface (Zn) necessitating the need to remove or destroy the oxide film without using high temperature and high load. Hence, in this study, the aim is to treat the bonding surface with formic acid for the removal of oxide film and substitution to a metal salt to determine the effectiveness of such treatment by performing tensile test and observation on the fractured surface of samples. From this study, it is found out that the tensile strength of the joint increased with the rise in bonding temperature with or without metal salt generation processing. However, it is understood that with metal salt generation processing, high strength joint can be obtained with lower bonding temperature compared with unmodified joints. It is hypothesized that this is because metallic zinc is generated as a result of surface modification and thermal decomposition of formate in the bond interface at low bonding temperatures.

Transient Liquid Phase Diffusion Bonding of 6061Al-15 wt.% SiC p Composite Using Mixed Cu-Ag Powder Interlayer

Microstructure and shear strength of transient liquid phase diffusion bonded (560 °C, 0.2 MPa) 6061Al-15 wt.% SiCp extruded composite using a 50-µm-thick mixed Cu-Ag powder interlayer have been investigated. During isothermal solidification that took 2 h for completion, a ternary liquid phase formed due to diffusion of Cu and Ag in Al. Subsequent cooling formed a ternary phase mixture (α-Al + CuAl2 + Ag2Al) upon eutectic solidification. With mixed Cu-Ag powder interlayer, isothermal solidification was faster than for pure Al joints made using a 50-µm-thick Cu foil interlayer and for the composite joints made using a 50-µm-thick Cu foil/powder interlayer under similar conditions. The presence of brittle eutectic phase mixture (CuAl2 + Ag2Al) led to poor joint strength at short TLP bonding times. The mixture disappeared upon isothermal solidification with a 2-h hold yielding improved joint strength even with solidification shrinkage in the joint. Increased holding time (6 h) erased shrinkage via solid state diffusion and yielded the highest joint strength (87 MPa) and fair joint efficiency (83%).

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.

Microstructures and Mechanical Properties of Transient Liquid-Phase Diffusion-Bonded Ti3Al/TiAl Joints with TiZrCuNi Interlayer

Transient liquid-phase diffusion bonding of Ti3Al-based alloy to TiAl intermetallics was conducted using Ti-13Zr-21Cu-9Ni (wt pct) interlayer foil. The joint microstructures were examined using a scanning electron microscope (SEM) equipped with an electron probe micro-analyzer (EPMA). The microhardness across the joint was measured and joint strengths were tested. The results show that the Ti3Al/TiAl joint mainly consists of Ti-rich phase, Ti2Al layer, α2-Ti3Al band, and residual interlayer alloy dissolved with Al. The amount of residual interlayer at the central part of the joint is decreased with the increase of the bonding temperature, and meantime the Ti2Al and α2-Ti3Al reaction bands close to the joined Ti3Al-based alloy become thickened gradually. Furthermore, the central part of the joint exhibits the maximum microhardness across the whole joint. The joints bonded at 1193 K (920 °C) for 600 seconds with a pressure of 2 MPa presented the maximum shear strength of 417 MPa at room temperature, and the strength of 234 MPa was maintained at 773 K (500 °C).

Transient liquid phase diffusion bonding of Ti–24Al–15Nb–1Mo alloy to TiAl intermetallics

Transient liquid phase (TLP) diffusion bonding of a Ti3Al-based alloy and TiAl intermetallics was firstly conducted with Ti–15Cu–15Ni (wt%) interlayer. Ti2Al layer, α2-Ti3Al band, Ti-rich phase, Ti2Ni and Ti2Cu compounds were formed within the joint and the joint showed a low shear strength of 74–79MPa. For the newly designed Ti–Zr–Cu–Ni–Co system filler alloy, the bonded joint mainly consisted of Ti-rich phase, Ti2Al layer, (Ti, Zr)2Al phase and (Ti, Zr)3Al dissolved with Cu, Ni and Co. The joints bonded at 1253K for 600s with a pressure of 2MPa presented the maximum shear strength of 435MPa at room temperature, and the strength of 234MPa was maintained at 873K. CuZr and Zr2Ni phases rather than Ti2Ni and Ti2Cu compounds were formed within the latter joint. The formation of the CuZr and Zr2Ni phases as well as the plastic α-Ti phase increased the joint ductility to a great extent.