Interfacial Reaction Layer Research Articles

Cold metal transfer welding–brazing of magnesium to pure copper

Magnesium alloy AZ31B and pure copper T2 were lapped and joined by cold metal transfer (CMT) welding–brazing method by AZ61A magnesium alloy wire with a 1·2 mm diameter. Results indicated that a satisfied Mg/Cu CMT welding–brazing joint was obtained in the stable welding processes with no spatter. The joint was composed of Mg–Mg welding joint formed between the Mg weld metal and the Mg base metal, and Mg–Cu brazing joint formed between the Mg weld metal and the local molten Cu base metal. The microstructure and the intermetallic compound (IMC) distribution were inspected and analysed in detail. The interfacial reaction layers of the brazing joint consisted of Mg2Cu, Al6Cu4Mg5, MgCu2 and Mg17Al12 IMCs. The tensile shear strength of the Mg/Cu CMT welding–brazing joint could reach 172·5 N mm−1. In addition, two different fracture modes were observed: at the fusion zone and at the brazing interface.

Influence of Welding Heat Input on Microstructure of Ti/Al Joint During Pulsed Gas Metal Arc Welding

Pulsed gas metal arc welding of titanium alloy Ti-2Al-Mn to aluminum 1060 using AlSi5 filler metal was conducted. Microstructures of Ti/Al joints with different welding heat input were investigated. Chemical composition and phase constituent near Ti/Al interface were analyzed. Microhardness distribution of the weld zone was tested. Binary intermetallic TiAl3 precipitations were formed in the weld metal, and it was concluded that morphology of TiAl3 precipitation varies with variation of welding heat input. Welding heat input also has a great influence on microstructure of Ti/Al interface. With a low welding heat input, the intermetallics TiAl3 were formed as a serrate reaction layer near the Ti/Al interface. With a higher welding heat input, multilayered interfacial reaction layers that consist of TiAl3, Ti7Al5Si12, and α-Ti layers were formed near the Ti/Al interface. Joints without defects were obtained when welding heat input was 1.85–2.10 kJ/cm.

Characterization of the Si3N4/42CrMo joints vacuum brazed with Pd modified filler alloy for high temperature application

The Si3N4 ceramic were brazed to 42CrMo steel by using Ag54.67–Cu35.96–Ti4.37–Pd5 (at.%) filler alloy. Effect of brazing temperature and dwelling time on the microstructure and mechanical properties of the joints were investigated. The results show that a double reaction layer which is composed of TiN and Ti5Si3 was formed at the Si3N4 ceramic/filler alloy interface. A continuous reaction layer consisting of TiC was also detected adjoining to 42CrMo steel. The central part of the joint was made up of Ag–Cu eutectic and CuPdTi reaction phases. With increasing brazing temperature, the thickness of brazing layer was gradually decreasing. Besides, partial stripy Cu[Ag] solid solution was transformed into blocky Cu[Ag, Pd] solid solution. The interfacial reaction layer was not affected with prolonging the dwelling time. However, more CuPdTi reaction phases were precipitated. The maximal bending strength of 352.3 MPa was obtained when the joint was brazed at 920 °C for 30 min. The bending strength of the joint could still maintain 216.56 MPa while the testing temperature was 500 °C. Pd modified filler alloy could significantly improve the joint high temperature properties since Pd element altered the phase composition and reduced the probability of oxidation at high temperature.

Observation of surface Dirac cone in high-quality ultrathin epitaxial Bi2Se3 topological insulator on AlN(0001) dielectric.

Bi2Se3 topological insulators (TIs) are grown on AlN(0001)/Si(111) substrates by molecular beam epitaxy. In a one-step growth at optimum temperature of 300 °C, Bi2Se3 bonds strongly with AlN without forming interfacial reaction layers. This produces high epitaxial quality Bi2Se3 single crystals with a perfect registry with the substrate and abrupt interfaces, allowing thickness scaling down to three quintuple layers (QL) without jeopardizing film quality. It is found by angle-resolved photoelectron spectroscopy that, remarkably, Bi2Se3 films maintain the 3D TI properties at very low thickness of 3QL (∼2.88 nm), exhibiting top surface gapless metallic states in the form of a Dirac cone.

Fabrication and characterization of NiTi/Ti3SiC2 and NiTi/Ti2AlC composites

Spark plasma sintering (SPS) was used as a fast consolidation technique to reduce reactions during powder consolidation of highly reactive systems (shape memory alloy/ternary carbide composites), which could not otherwise be fabricated using conventional methods. NiTi/Ti2AlC and NiTi/Ti3SiC2 powder mixtures, each with a 50/50 volume ratio, were processed in the 1233–1373K temperature range under 100–300MPa for 3 to 30min. Martensitic phase transformation behavior of the composites was studied using differential scanning calorimetry and was compared with starting powders to evaluate the transformable NiTi in the composites. The effects of starting materials and processing conditions (sintering temperature, soaking time, and sintering pressure) on densification, reaction, and transformable NiTi were studied. A high-pressure (300MPa) run at 1233K for 8min produced a fully-dense NiTi/Ti3SiC2 composite with a maximum percent of transformable NiTi. Based on the phase analysis on the interfacial reaction layers, we developed the reaction mechanisms between NiTi and Ti3SiC2 or Ti2AlC during SPS. The results suggest that SPS is a viable technique to fabricate highly reactive ceramic–metal system with active components.

In SituObservation on Lime Dissolution in Molten Metallurgical Slags – Kinetic Aspects

The chemical dissolution of lime particles in molten CaO–Al2O3–SiO2-based slags was observed by using a confocal scanning laser microscope (CSLM) in a temperature range from 1450 to 1600 °C. The dissolution behavior was found to be largely dependent on temperature and slag chemistry. A considerable increase in the dissolution rate was observed at elevated temperatures. The in situ observations revealed that the dissolution process in the slags containing MgO was controlled by chemical reactions at the interface. For slags without MgO, the dissolution could be divided into three stages when an interfacial reaction (IR) layer formed at the interface. The dissolution was limited by chemical reactions during the early stage, a mixed control of product layer and boundary layer diffusion during the intermediate stage, and boundary layer diffusion control in the final stage. The IR layer formed during dissolution at the interface between the lime particles, and the liquid slag free of MgO was clearly a kinetic barrier for dissolution. A dissolution factor was defined to evaluate the dissolution mechanisms quantitatively by coupling the resistance and the driving forces of dissolution in different slags. This factor provided direct evidence that the addition of MgO in CaO–Al2O3–SiO2 slags is beneficial for lime dissolution.

Interface Remelting of Tungsten Carbide Particles Reinforced Steel Composite

A tungsten carbide particles reinforced steel matrix composite was fabricated by spark plasma sintering(SPS) technique, and then the composite was remelted in a vacuum tube furnace. The effect of remelting temperature on interface reaction was investigated meticulously. The results show that the interface reaction could occur when the matrix was still in solid state, the thickness of interface reaction layer increased with the increasing temperature. The interface reaction product, Fe3W3C, was resulted from the following two step reactions: firstly the reaction 2WC→W2C+C would occur within tungsten carbide particles at 1314℃, then the W2C would react with Fe to produce Fe3W3C at temperatures above1341℃.

Study on cold metal transfer welding–brazing of titanium to copper

3mm Pure titanium TA2 was joined to 3mm pure copper T2 by Cold Metal Transfer (CMT) welding–brazing process in the form of butt joint with a 1.2mm diameter ERCuNiAl copper wire. The welding–brazing joint between Ti and Cu base metals is composed of Cu–Cu welding joint and Cu–Ti brazing joint. Cu–Cu welding joint can be formed between the Cu weld metal and the Cu groove surface, and the Cu–Ti brazing interface can be formed between Cu weld metal and Ti groove surface. The microstructure and the intermetallic compounds distribution were observed and analyzed in details. Interfacial reaction layers of brazing joint were composed of Ti2Cu, TiCu and AlCu2Ti. Furthermore, crystallization behavior of welding joint and bonding mechanism of brazing interfacial reaction were also discussed. The effects of wire feed speed and groove angle on the joint features and mechanical properties of the joints were investigated. Three different fracture modes were observed: at the Cu interface, the Ti interface, and the Cu heat affected zone (HAZ). The joints fractured at the Cu HAZ had higher tensile load than the others. The lower tensile load fractured at the Cu interface or Ti interface was attributed to the weaker bonding degree at the Cu interface or Ti interface.

Interfacial Reaction Thermodynamics between Sn-Cu-Ag Solder and Ni Substrate

Interfacial reaction during wetting and spreading of Sn-Ag-Cu solder on Ni substrate is a key factor in order to improve the mechanical properties of the joints and the weld quality. Therefore, it’s important to focus on the thermodynamic and kinetic analysis of this interface reaction. In this paper, the sessile drop method was used to study the spreading contour evolution. The Kissinger method was used to calculate thermo-kinetic parameters of reactions between Sn-Ag-Cu solder and Ni substrate based on DTA data. The results show that Cu reduces activation energy and reaction rate of Sn-Ag-Cu/Ni system. (Cu, Ni)6Sn5 phase mainly constitute the interface reaction layer of Sn-Ag-Cu/Ni. As the temperature increases, partial (Cu, Ni)6Sn5 phase is substituted by Ni3Sn4 phase.

Microstructure and joining mechanism of Ti/Al dissimilar joint by pulsed gas metal arc welding

Butt joining of titanium alloy Ti–2Al–Mn to aluminum 1060 using AlSi5 filler wire was conducted using pulsed gas metal arc welding. Joining mechanism of Ti–2Al–Mn/Al 1060 dissimilar joint with different welding heat input was investigated. Formations of precipitation and Ti/Al interface were discussed in detail. Fusion zone near aluminum is composed of α-Al dendrites and Al–Si hypoeutectic structures. A few TiAl3 precipitations appear in the weld metal owing to metallurgical reactions of Al with dissolved Ti. When the welding heat input was in the range of 1.87–2.10 kJ/cm, titanium alloy Ti–2Al–Mn and Al 1060 were joined together by the formation of a complex Ti/Al interface. With a low welding heat input, a serrate TiAl3 interfacial reaction layer was formed near Ti/Al interface. With the increasing of the welding heat input, α-Ti, Ti7Al5Si12, and TiAl3 layers were formed orderly from Ti–2Al–Mn to weld metal.

Effect of Heat Treatment on the Mechanical Properties of Roll-Bonded Al3003/STS439 Hybrid Plate

In this study, roll-bonded Al/STS clad was heat-treated at various temperature (200-600 °C) for 1hour and then their mechanical performance and interfacial structure was studied. To estimate the mechanical properties of heat-treated clad materials at various temperatures, the tension tests were performed. For Al/STS clad heat-treated from 200 °C to 500 °C, no interfacial reaction layer was observed. Brittle intermetallic layer was observed between Al and STS, which induced the interface crack due to the large mismatch of the thermal expansion coefficient between two metal plates. XRD peaks from the interface region indicate the presence of Al2Fe, Al5Fe and Al13Cr2 in addition to Fe, Cr, Al and Mn. The UTS of Al/STS sheet was observed to follow the rule of mixture. One noticeable observation from stress-strain responses is that the fracture strain of Al/STS clad sheet increased markedly more than that of Al clad sheet by the increasing heat treatment temperature.

Interface Reaction between Ceramic Moulds and High Nb-TiAl Alloys

Abstract The interface reaction between Ti-44Al-8Nb-0.2W-0.1B-0.1Y (at%) alloy and Al 2 O 3 /ZrO 2 /Y 2 O 3 crucibles was investigated. The thicknesses of the interface reaction layers are about 40, 170 and 20 μm. The most interesting is the microstructure transformation of Ti-44Al-8Nb-0.2W-0.1B-0.1Y solidifying in different crucibles. After solidifying in Al 2 O 3 /ZrO 2 /Y 2 O 3 crucibles, the oxygen contents in Ti-44Al-8Nb-0.2W-0.1B-0.1Y alloy are measured to be 0.35, 0.41 and 0.11 (at%). During melting and solidification, oxygen in crucibles will diffuse into the alloy matrix. High oxygen content causes microstructure transformation. Peritectic reaction occurs in the alloys solidifying in Al 2 O 3 and ZrO 2 crucibles. For contrast, Ti-49.5Al-2Cr-2Nb alloy was chosen to make investigation. No visible microstructure difference is found in alloys solidified in various crucibles though the oxygen contents are determined as 0.40, 0.63 and 0.25 (at%).

Determination of band alignment of pulsed-laser-deposited perovskite titanate/III-V semiconductor heterostructure using X-ray and ultraviolet photoelectron spectroscopy

Techniques of X-ray and ultraviolet photoelectron spectroscopy are performed to investigate the energy band discontinuity of pulsed-laser-deposited SrTiO3 (STO)/GaAs heterostructure. The valence band offset is determined to be 2.6 eV, while the conduction band offset is deduced to be 0.7 eV. As a consequence, an energy band diagram of STO/GaAs with a type II band alignment forming at the interface is precisely constructed. The chemical states across the STO/GaAs interface are investigated by sputter-depth profile, and there are no detectable interfacial reaction and intermediate layer occurring between the epitaxial STO film and GaAs substrate.

Study on the interface reaction behavior of NiCrAlY coating on titanium alloy

NiCrAlY coating was deposited on TC4 (Ti–6Al–4V) titanium alloy substrate by arc ion plating (AIP). After vacuum heat treatments, the interface reaction behavior of NiCrAlY coating/TC4 substrate was studied. The results show that the 20μm as-deposited coating, which was made up of γ-Ni, α-Cr and β-NiAl phases with 50–200nm grain size, was continuous and tightly bound to the substrate. The allotropic transformation of α-Ti to β-Ti during the heat treatment had a significant influence on the interface reaction behavior. After vacuum heat treatment below the allotropic transformation temperature (ATT) of titanium, i.e. 750°C, Ni3(Al, Ti)/TiNi/Ti2Ni/Ti3Al and α-Ti/β-Ti stabilized layer formed in turn from the coating to substrate at the interface. At 870°C or 900°C (near/above the ATT of titanium), Cr began to take part in the interface reaction and α-TiCr2 phase was detected. With the increase of heat treatment time at 900°C, including the coating phases, all the interface products decomposed and solved in the substrate to form a thick β-Ti stabilized layer for the higher solid solubility of the coating elements in β-Ti. The decomposition of the coating led to its total degradation. The interface reaction processes were studied in terms of thermodynamic and kinetic factors. Based on Fick's first law, the relation between the thickness of interface reaction layer and heat treatment time was discussed.

Phase evolution and nature of oxide dissolution in metallurgical slags

The dissolution of solid lime particles into liquid slags at high temperatures was evaluated by means of confocal scanning laser microscopy. An additional solid layer around the lime particle was observed at the intermediate stage of the dissolution into CaOAl2O3SiO2 slags. The dissolution rate was decelerated due to the existence of the additional layer and the dissolution profile could be clearly distinguished into three stages, that is, an early, intermediate, and late stage. By adding 10 wt % MgO, this layer could be effectively eliminated and the slope of the whole dissolution profile kept relatively constant. The dissolution path and mechanisms were subsequently evaluated by incorporating thermodynamic calculations. Both direct and indirect dissolutions could be distinguished. It was realized that the decrease in composition range for solid precipitating after adding MgO could significantly reduce the interfacial reaction (IR) layer formation. Post‐mortem analyses on quenched samples were further carried out to confirm the theoretical calculations. It was found that the solid layer in slags without MgO was (CaO)2·SiO2 and (CaO)3·SiO2 which is in line with the thermodynamic calculations. However, only (CaO)2·SiO2 was noticed in slags with MgO which both (CaO)2·SiO2 and MgO phases should be present according to the calculations. The nonequilibrium during dissolution may play an important role on phase transformation and MgO particles in much smaller quantity may have dissolved into (CaO)2·SiO2 phase. The diffusion of CaO in both slags with and without MgO was additionally investigated. The local CaO concentration distributions from the direct dissolution phase to the slag bulk could be well fitted with the theoretical model proposed via Fick's second law. As a result, the local diffusion coefficient in the dissolution region was obtained and the effect of MgO addition on diffusion could be assessed. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2907–2916, 2013

Microscale evaluation of mechanical properties of friction stir welded A6061 aluminium alloy/304 stainless steel dissimilar lap joint

Microscale evaluation of the mechanical properties of a friction stir welded A6061/SUS 304 grooved lap joint was performed using a microtensile test and transmission electron microscopy. The microtensile test revealed that ∼62% of the area along which the rotating tool passed the specimen was regarded as the bonded region and that the joint was fractured at the A6061 matrix owing to the formation of very thin interfacial reaction layers. Equiaxed aluminium grains were observed at the interface of the specimen after it was fractured, indicating that the interface deformed only slightly during the microtensile test. It should be noted that although the maximum tensile strength of the joint was approximately the same as that of the base alloy, the proof stress of the joint decreased with the dissolution of the β″ phase in the A6061 aluminium alloy.

Effect of heat treatment on the bending behavior of tri-layered Cu/Al/Cu composite plates

Bending and fracture behaviors of tri-layered Cu/Al/Cu composite plates were processed by roll-bonding and the effects of work hardening and displacement rate sensitivity during bending on the overall bending behavior and fracture were investigated. As-roll-bonded composite exhibited the extensive load plateau before a relatively rapid load drop. The more localized bending in the as-roll-bonded Cu/Al/Cu clad composite can be attributed to the near-zero work hardening rate in bending. For the Cu/Al/Cu composites annealed at 300°C and up to 450°C, the pronounced work hardening during bending tends to distribute the bending deformation uniformly. For the as-roll-bonded Cu/Al/Cu composite, a fatal crack perpendicular to the Cu/Al interface through the bottom Cu layer was formed by the large tensile stress associated with the severely localized bending. A large crack parallel to the interface adjacent to the fatal crack through the bottom Cu layer appeared to have propagated in Al layer, not along the interface between Al and the bottom Cu layer, suggesting the excellent bonding between Al and Cu in the as-roll-bonded Cu/Al/Cu. For annealed clad composites at 500°C, the localized bending is thought to be caused by the growth of cracks along the interface reaction layer, resulting in the fracture of bottom Cu layer.

Interface kinetic diffusion reaction leading to fast and continuous generation of AgCl nanocubes in NaCl solution

It is found that the electrochemical corrosion of a silver sheet anode in NaCl solution gives rise to a fast and continuous way of generating AgCl nanocubes with good uniform morphology. We examined the factors affecting the size and morphologies of AgCl nanocubes, which include the applied voltage, the concentration of NaCl, and that of Na2SO4 added to enhance the conductivity of the NaCl solution as well as the physical ways of solution mixing and the placement of the Ag sheet anode with respect to the Pt cathode. Analysis of these factors indicates that the fast and continuous generation of AgCl nanocubes requires the presence of the interface reaction layer formed by the kinetic diffusion of Ag(+) and Cl(-) ions. The AgCl nanocubes possess {001} facets and uniform morphology, and the Ag@AgCl nanocubes have much higher photocatalytic activity than do the irregularly-shaped Ag@AgCl particles made from the conventional precipitation method.

CO2 laser welding–brazing characteristics of dissimilar metals AZ31B Mg alloy to Zn coated dual phase steel with Mg based filler

The influence of process variables including heating mode, flux, laser beam offset, and travel speed on the weld bead geometry and joint strength was investigated during laser welding–brazing (LWB) of AZ31B Mg alloy to Zn coated steel. The wettability of molten filler metal on steel surface was studied via a Charge-coupled Device (CCD) camera. The reaction layers along the interface were characterized and the failure mechanism was identified. Dual beam processing was found to preheat the steel substrate and promote the wettability of molten filler metal on the steel surface, thereby improving the corresponding joint strength. Utilizing a flux was found to produce a similar effect on molten filler metal. The optimized range of laser offset was found to be between 0.5 and 1.0mm toward the steel side of the joint. These optimized parameters led to a maximum joint strength of 228N/mm. The joint strength was however found to decrease with increasing travel speed. Cracking was identified with travel speeds greater than 1m/min. Microstructural characterization showed that heterogeneous interfacial reaction layers were produced from the seam head to the seam root of the joint. The reaction layer thickness varied within a certain range when applying different process parameters, suggesting the growth of interfacial layer was not essentially related to the heat input. The primary failure mode of the lap specimens was interfacial fracture. Cracks propagated along the Mg–Zn reaction layer and steel interface. Original Fe–Al phase formed during the hot-dip galvanization process hindered the metallurgical bonding of Mg–Zn reaction layer and steel substrate, which was attributed to interfacial type failure.

Interface evolution of the Cf/leucite composites derived from Cf/geopolymer composites

In this paper, effect of heat treatment temperature on the interface structure of the carbon fiber reinforced geopolymer composites was investigated by transmission electron microscopy (TEM), selected-area diffraction (SAD) analysis and high-resolution transmission electron microscopy (HRTEM). In the composite treated at 1100°C, carbon fiber showed a good bond with the leucite matrix and no interface reaction layer was observed, while due to the thermal mismatch between fiber and matrix, microcrack which was perpendicular to the fiber axial direction can be seen in the matrix. With increase in heat treatment temperature to 1200, 1300 and 1400°C, interface reaction occurred and reaction layers with thickness of 50, 100 and 1000nm, respectively, were detected. The interface layer was formed by the reaction between Si–O groups in the matrix and C element in the fiber. Especially for the sample treated at 1400°C, serious interface reaction led to the formation of β-SiC and property of carbon fiber was greatly degraded.