Thickness Of Intermetallic Layer Research Articles

Intermetallic layers in temperature controlled Friction Stir Welding of dissimilar Al-Cu-joints

Friction Stir Welding (FSW) can be performed to join dissimilar metal combinations like aluminium and copper, which is of high interest in modern production of electrical applications. The amount of intermetallic phases in the weld seam is significantly reduced compared to traditional fusion welding technologies. Because the solidus temperature is typically not reached during FSW, the growth of intermetallic phases is impeded and the intermetallic layer thicknesses typically remains on the scale of a few hundred nanometres. These layers provide a substance-to-substance bond, which is the main joining mechanism. Latest research confirms that the layer formation is most likely driven by the heat input during processing. Hence, the welding temperature is the key to achieve high quality joints. In this study, aluminium and copper sheets were welded in lap joint configuration using temperature-controlled FSW. An advanced in-tool measurement set-up was used to determine precise temperature data. Scanning electron microscopy (SEM) was used to analyse metallurgical aspects (e.g. structure and composition of the intermetallic phases) of the joints. The results show a correlation between the welding temperature and the thickness of the intermetallic layer and its structure. The temperature control significantly improved the correlation compared to previous studies. This leads to an enhanced understanding of the dominating joining mechanisms.

Yb: YAG laser welding of dual phase steel to aluminium alloy

In this work, laser welding of dual phase steel (DP 600) to aluminium alloy (AA 6061) was studied both experimentally and by computational modeling. Three different laser energy densities (640 J/mm2, 850 J/mm2 and 1250 J/mm2) were chosen to study the effect of heat input on microstructural changes and strength of the joint. It was inferred from the results that the laser energy density had a direct influence on the formation of intermetallic phases such as Fe2Al5 and FeAl3. At relatively high laser energy density (1250 J/mm2), thick intermetallic layer and crack propagations were observed at the interface of the weld, which deteriorated the strength of joint. Whereas, maintaining the laser energy density at 850 J/mm2 enhanced the weld quality by lowering the intermetallic thickness in the range of 6–10 μm and defects such as cracks were also lowest at the weld interface. The formation of the cracks in the interfacial region was largely influenced by the hard and brittle intermetallics, which was evident from the microhardness results. The microhardness value along the interface exhibited a maximum of 836 HV at 1250 J/mm2, which was much higher than the base metal hardness (AA 6061 – 65 HV, DP 600 - 255 HV). A two-dimensional computational model was used to predict the temperature histories at different laser energy densities during welding. The results of the computational model (penetration depth and material ablation) correlated well with the experimental results.

Modeling of high-power ultrasonic welding of Cu/Al joint

Ultrasonic metal welding is still an indistinct but useful manufacturing technology. A three-dimensional finite element model was developed to investigate this dynamic welding, including temperature rise, material deformation, and growth of intermetallic compounds. Heat generation at the upper and bottom interfaces, material softening, and high convection boundary conditions was considered. The results show that sonotrode tip teeth penetration starts earlier and increases rapidly, reaching the maximum, but anvil tip penetration starts later and increases slowly. The plastic deformation area of welding zone increases exponentially. Plastic strain is mainly generated in the welding zone, and the total plastic strain of welding zone is approximately proportional to the displacement of sonotrode tip. The thickness of intermetallic layer was dominated by ultrasonic action rather than interface temperature. The model was validated by comparing the predicted temperature, sonotrode displacement, and profile of weld cross section with the experimental results, exhibiting a good agreement.

Influence of Bi Addition on Wettability and Mechanical Properties of Sn-0.7Cu Solder Alloy

The effect of bismuth (Bi) micro-alloying additions on wettability and mechanical properties of Sn-0.7Cu lead-free solder were explored. This paper also investigates the influences of various Bi percentages on the suppression of intermetallic compound formation. Scanning electron microscope (SEM) was used to observe the microstructure evolution of solder joint including the thickness of interfacial intermetallic layers. Overall, with the addition of Bi to Sn-0.7Cu solder, the size of primary Cu6Sn5become smaller and suppresses the thickness of interfacial intermetallic compound between solder and the Cu substrate. Microhardness value and wetting properties also increased with Bi addition which resulted in smaller size of β-Sn and Cu6Sn5.

Influence of thickness of zinc coating on CMT welding-brazing with AlSi5 alloy wire

Effect of thickness of zinc coating on Cold Mattel Transfer (CMT) brazing of aluminum and galvanized steel is investigated. The thickness of zinc coating is 10 μm, 30 μm, and 60 μm, respectively. A high-speed camera was used to capture images of welding process of different specimens; the microstructure and composition analyses of the welding seam were examined by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS); the mechanical properties were measured in the form of Nano-indentation experiments. The results showed that arc characteristics and metal transfer behavior were unsteady at the beginning of welding process and that became stable after two cycles of CMT. With the thickness of zinc coating thickening, arc characteristics and metal transfer behaviors were more deteriorated. Compared with 10 μm and 30 μm, clad appearance of 60 μm was straight seam edges and a smooth surface which wetting angle was 60°. Zinc-rich zone at the seam edges was formed by zinc dissolution and motel pool oscillating, and zinc content of 10 μm and 30 μm were 5.8% and 7.75%. Zinc content of 60 μm was 14.61%, and it was a belt between galvanized steel and welding seam. The thickness of intermetallic compounds layer was in the range of 1–8 μm, and it changed with the thickness of zinc coating. The average hardness of the reaction layer of 60 μm is 9.197 GPa.

Microstructure, growth kinetics and mechanical properties of interface layer for roll bonded aluminum-steel clad sheet annealed under argon gas protection

In this paper, an annealing treatment was performed to eliminate the work hardening effect of cold roll-bond clad sheets, and the effect of annealing temperature and time on the microstructure evolution at steel/aluminum interface and mechanical properties of aluminum-steel clad sheet were investigated. Results showed that the longer the time and the higher the temperature are, the thicker the inter-diffusion zone become. Fe2Al5 phase preferentially formed at the inter-diffusion layer at 600 °C. As the annealing temperature increased, another FeAl3 phase gradually formed. The thickness of intermetallic compound layers over 10 μm would seriously deteriorated the mechanical properties of aluminum-steel clad sheet. Furthermore, the relationship of the thickness of inter-diffusion layer with the annealing time and temperature was established, which played a vital role in predicting the working time of aluminum-steel clad sheet.

Microstructure and Reliability of Tin-Silver Micro-Copper Pillar Assemblies

Abstract IBM engineers recently conducted a study to better understand and control the reliability of copper pillar solder joints in 2.5-D packages. Here they describe their approach and the results they obtained. They explain how they created test samples to evaluate different solder compositions, pillar geometries, and thermal histories and assess their effect on microstructure, precipitate morphology, intermetallic layer thickness, and shear strength. They also present thermal cycling test results comparing the performance of silicon and glass interposers.

Influence of process parameters on thermal cycle and intermetallic compounds formation in high speed laser weld-brazing of aluminium-steel angle joints

AA6016-T4 aluminium and DX56D+Z140M steel sheets were joined by fluxless laser weld-brazing process with ER4043 AlSi5 filler wire at high brazing speed. The configuration studied corresponds to typical automotive roof/body-side angle joints. At the interface, the measurements of thermal cycle are performed with K-thermocouples. The results are compared to simulated thermal cycles obtained through SYSWELD Software. Thermal cycles are evaluated with the maximal temperature reached, the time of interaction at high temperature and the cooling speed. Several combinations of laser power and brazing speed are both investigated experimentally and by simulation to study their influence on the thermal cycle and the intermetallic layer thickness. Thermal cycles are discretized to calculate the theoretical growth of the intermetallic compounds with a diffusion-based model. The result is compared to experimental intermetallic layer measured with optical microscopy. The power tends to influence both the maximal temperature and the cooling speed whereas the brazing speed only influences the maximal temperature. The calculation demonstrates the capability to distinguish the process configuration which will lead to the thickest intermetallic layer.

Effects of Zinc Oxide Nanoparticles on Properties of SAC0307 Lead‐Free Solder Paste

This research investigates the effects of zinc oxide (ZnO) nanoparticles of varying concentrations 0.0, 0.25, 0.50, 0.75, and 1.0 wt.% on the melting temperatures, wettability, printability, slump, and interfacial microstructure of the ZnO‐doped Sn‐0.3Ag‐0.7Cu lead‐free solder pastes on the copper substrate. The results revealed that the introduction of the ZnO particles had no effect on the solidus and liquidus temperatures of the solders. The maximum wettability was achieved with 0.25 wt.% ZnO nanoparticles, while the printability was inversely correlated with the nano‐ZnO concentrations. The findings also indicated that, at room temperature, the slumping and the nano‐ZnO concentrations were positively correlated and that, under the 150°C thermal condition, the maximum slumping was achieved with 0.25 wt.% ZnO. The slumping mechanism of the SAC0307‐xZnO solder pastes is also provided herein. Moreover, the experiments showed that Cu6Sn5 was the single intermetallic compound present in the interfacial layer between the solders and the copper substrate, with the maximum intermetallic layer thickness realized at the 0.25 wt.% ZnO concentration.

Effects of heat treatment on the intermetallic compounds and mechanical properties of the stainless steel 321–aluminum 1230 explosive-welding interface

The effects of heat treatment on the microstructure and mechanical properties of intermetallic compounds in the interface of stainless steel 321 explosively bonded to aluminum 1230 were investigated in this study. Experimental investigations were performed by optical microscopy, scanning electron microscopy, and microhardness and shear tensile strength testing. Prior to heat treatment, increasing the stand-off distance between samples from 1 to 2.5 mm caused their interface to become wavy and the thickness of intermetallic layers to increase from 3.5 to 102.3 μm. The microhardness increased from HV 766 in the sample prepared at a stand-off distance of 1 mm to HV 927 in the sample prepared at a stand-off distance of 2.5 mm; in addition, the sample strength increased from 103.2 to 214.5 MPa. Heat treatment at 450°C for 6 h increased the thickness of intermetallic compound layers to 4.4 and 118.5 μm in the samples prepared at stand-off distances of 1 and 2.5 mm, respectively. These results indicated that increasing the duration and temperature of heat treatment decreased the microhardness and strength of the interface of explosively welded stainless steel 321−Al 1230 and increased the thickness of the intermetallic region.

AA6082 to DX56-Steel Laser Brazing: Process Parameter–Intermetallic Formation Correlation

In the present study, laser-brazed AA6082 to DX56-galvanized steel joints were investigated to understand the influence of process parameters on joint strength in terms of intermetallic layer formation. 1.5-mm-thick sheet of aluminum alloy (AA6082-T6) and galvanized steel (DX56) sheet of 0.7 mm thickness were laser-brazed with 1.5-mm-diameter Al-12% Si solid filler wire. During laser brazing, laser power (4.6 kW) and wire feed rate (3.4 m/min) were kept constant with a varying laser scan speed of 3.5, 3, 2.5, 2, 1.5, and 1 m/min. Microstructure of brazed joint reveals epitaxial growth at the aluminum side and intermetallic layer formation at steel interface. Intermetallic layer formation was confirmed by EDS analysis and XRD study. Hardness profile showed hardness drop in filler region, and failure during tensile testing was initiated through the filler region near the steel interface. As per both experimental study and numerical analysis, it was observed that intermetallic layer thickness decreases with increasing brazing speed. Zn vaporization from galvanized steel interface also affected the joint strength. It was found that high laser scan speed or faster cooling rate can be chosen for suppressing intermetallic layer formation or at least decreasing the layer thickness which results in improved mechanical properties.

Method for Semi-Automated Measurement and Statistical Evaluation of Iron Aluminum Intermetallic Compound Layer Thickness and Morphology

In the present study, a semi-automated method for the measurement of intermetallic compound layer thicknesses is introduced. Based on backscattered electron contrast images of the bond zones that feature a sufficient contrast between the substrates and the intermetallic compound layer, every line of pixels perpendicular to the bond zone is analyzed. This provides the opportunity to evaluate the distribution of the measured single thicknesses to describe the layer morphology quantitatively. It is shown that it is possible to identify several morphological features by employing certain statistical values. Commonly used measurement methods are compared to the results of the proposed method to show its applicability.

Microstructural and Phase Composition Differences Across the Interfaces in Al/Ti/Al Explosively Welded Clads

The microstructure and phase composition of Al/Ti/Al interfaces with respect to their localization were investigated. An aluminum-flyer plate exhibited finer grains located close to the upper interface than those present within the aluminum-base plate. The same tendency, but with a higher number of twins, was observed for titanium. Good quality bonding with a wavy shape and four intermetallic phases, namely, TiAl3, TiAl, TiAl2, and Ti3Al, was only obtained at the interface closer to the explosive material. The other interface was planar with three intermetallic compounds, excluding the metastable TiAl2 phase. As a result of a 100-hour annealing at 903 K (630 °C), an Al/TiAl3/Ti/TiAl3/Al sandwich was manufactured, formed with single crystalline Al layers. A substantial difference between the intermetallic layer thicknesses was measured, with 235.3 and 167.4 µm obtained for the layers corresponding to the upper and lower interfaces, respectively. An examination by transmission electron microscopy of a thin foil taken from the interface area after a 1-hour annealing at 825 K (552 °C) showed a mixture of randomly located TiAl3 grains within the aluminum. Finally, the hardness results were correlated with the microstructural changes across the samples.

Improving joint formation and tensile properties of friction stir welded ultra-thin Al/Mg alloy sheets using a pinless tool assisted by a stationary shoulder

In order to reduce or eliminate pin adhesion, a self-designed pinless tool with six-groove on a rotational shoulder was proposed to friction stir weld 6061-T6 Al and AZ31B Mg alloys. The assisted stationary shoulder can successfully improve surface formation, accelerate mechanical mixing, broaden welding process parameter window, heighten welding depth, and reduce the intermetallic compound layer thickness. Under the welding parameters of 40 mm/min, 1200 rpm, and 0.3 mm offset to Mg, sound joint with small flashes, sufficient Al/Mg mixture, and welding depth of 1 mm was obtained using the pinless tool assisted by the stationary shoulder. The maximum tensile strength of Al/Mg joint by the stationary shoulder reaches 124.1 MPa, which is 121.6% of that by the pinless tool. Some dimples appear on the fracture surface of the top region, presenting the existence of ductile fracture. Therefore, the pinless tool assisted by the stationary shoulder is greatly suitable for the welding of ultra-thin sheets of Al/Mg alloys.

Multiphysics Simulation and Experimental Investigation of Aluminum Wettability on a Titanium Substrate for Laser Welding-Brazing Process

The control of metal wettability is a key-factor in the field of brazing or welding-brazing. The present paper deals with the numerical simulation of the whole phenomena occurring during the assembly of dissimilar alloys. The study is realized in the frame of potential applications for the aircraft industry, considering the case of the welding-brazing of aluminum Al5754 and quasi-pure titanium Ti40. The assembly configuration, presented here, is a simplification of the real experiment. We have reduced the three-dimensional overlap configuration to a bi-dimensional case. In the present case, an aluminum cylinder is fused onto a titanium substrate. The main physical phenomena which are considered here are: the heat transfers, the fluid flows with free boundaries and the mass transfer in terms of chemical species diffusion. The numerical problem is implemented with the commercial software Comsol Multiphysics™, by coupling heat equation, Navier-Stokes and continuity equations and the free boundary motion. The latter is treated with the Arbitrary Lagrangian Eulerian method, with a particular focus on the contact angle implementation. The comparison between numerical and experimental results shows a very satisfactory agreement in terms of droplet shape, thermal field and intermetallic layer thickness. The model validates our numerical approach.

Cross-Beam Laser Joining of AA 6111 to Galvanized Steel in a Coach Peel Configuration

Cross-beam laser joining of aluminum alloy 6111 to hot-dip galvanized steel in the coach-peel configuration was investigated with the addition of AA 4047 filler wire. The filler material was not only brazed onto the galvanized steel but also partially fusion-welded with the aluminum panel. Through adjusting the laser power to 3.4 kW, a desirable wetting and spreading of filler wire on both panel surfaces could be achieved, and the thickness of intermetallic layer in the middle section of the interface between the weld bead and steel was less than 2 μm. To better understand the solid/liquid interfacial reaction at the brazing interface, two rotary Gaussian heat source models were introduced to simulate the temperature distribution in the molten pool by using the finite element method. Joint properties were examined in terms of microstructure and mechanical properties. During the tensile test, the fracture of coupons took place at the aluminum side rather than along the interface between the intermetallic layer and steel panel. No failure occurred during the three-point bending test.

Enhancing Friction Stir Weldability of 6061-T6 Al and AZ31B Mg Alloys Assisted by External Non-rotational Shoulder

In order to increase cooling rate and then reduce the amounts of intermetallic compounds, external non-rotational shoulder tool system derived from traditional tool in friction stir welding was used to join dissimilar Al and Mg alloys. In this study, based on the external non-rotational shoulder, the weldability of Al and Mg alloys was significantly improved. The non-rotational shoulder tool is propitious to make more materials into weld, increase cooling rate and then reduce material adhesion of rotational pin, obtaining sound joint with smaller flashes and smooth surface. Importantly, the thickness of intermetallic compounds layer is reduced compared with traditional tool. Meanwhile, hardness values of dissimilar joint present uneven distribution, resulting from complex intercalated structures in nugget zone (NZ) featured by intermetallic compound layers and fine recrystallized Mg and Al grains. Compared with traditional tool, non-rotational shoulder is beneficial to higher tensile properties of joint. Due to the intermetallic compound layer formed in the interface of Al-Mg, the welding joint easily fractures at the NZ, presenting the typical brittle fracture mode.

Welding Current and Shielding Gas Flow Rate Effect to The Intermetalic Layer Formation of Tungsten Inert Gas (Tig) on Dissimilar Metals Weld Joints Between Galvanized Steel and Aluminium Aa 5052 By Using Al-Si 4043 Filler

Tungsten Inert Gas welding of galvanized steel-aluminium useful for weight reduction, improve perform and reduce cost production. The effect of welding parameters, welding current and shielding gas flow rate on the intermetallic formation and hardness of dissimilar metals weld joint between galvanized steel and aluminium by using AA 5052 filler was determined. In this research, welding speed was consistent kept. The welding parameters were obtained by using welding currents of 70, 80 and 90 A, shielding gas flow rate of 10, 12 and 14 litre/min. The intermetallic layer thickness increased by welding currents of 70 A to 80 A, but then it dropped on 90 A. The higher of a shielding gas flow rate, the lower the thickness of the intermetallic layer. The higher of a welding current, the lower the hardness of weld. The higher of a shielding gas flow rate, the greater the hardness of weld. As a result,the maximum hardness by current variation of 70 A and a shielding gas flow rate of 14 Litre/min was 100.9 HVN.

Microstructural Characterization and Mechanical Properties of Diffusion Bonded Ti–Ni In Situ Metal Intermetallic Laminates

In this work, Ti–Ni based in situ metal intermetallic laminates (MILs) were prepared and the various intermetallic phases formed were analyzed. Solid state diffusion bonding technique was adopted to produce transition joints between commercially pure Ti and Ni sheets of thickness 0.5 and 0.2 mm respectively at three different temperatures such as 770, 800 and 850 °C for various bonding duration. Microstructural characterization and phase analysis along the cross section of the bonded samples revealed the presence of three different intermetallic phases namely Ti2Ni, TiNi and TiNi3. Quasi static compression tests carried out on the MILs along the parallel and perpendicular direction revealed that the strength of the MILs increased with increase in total intermetallic layer thickness. The fractographs taken on fracture surface revealed that the failure of the MILs was mainly due to the formation of brittle cracks and de-bonding in the intermetallic layers. However, the metallic layers added strength to the MILs.

Effect of Dwell Time on Joint Interface Microstructure and Strength of Dissimilar Friction Stir Spot-Welded Al-5083 and St-12 Alloy Sheets

Joining of Al-5083 alloy sheet to St-12 steel sheet was performed using a new friction stir spot welding (FSSW) technique in which the tool pin tip did not enter lower steel sheet. Effect of dwell time on the microstructure and mechanical properties of the joints was studied by various methods including microhardness measurements, shear test, stereo and light microscopy as well as scanning and transmission electron microscopy (SEM and TEM). Results indicated that compared to the conventional FSSW process, stronger joints can be achieved by this FSSW technique. Cross-sectional observation of the failed specimens indicated the occurrence of final fracture from the circumference of the tool pin where the Al sheet thickness was decreased as a result of the tool pin penetration. However, microhardness measurements introduced these fracture locations as the hardest regions of the Al part of welds. In addition to the Al3Fe and Al5Fe2 intermetallic compounds reported in the literature to form at the interface of dissimilar Al/steel joints, a third layer of AlFe intermetallic compound was also identified adjacent to the steel side of welds. Enhancement of the dwell time from 5 to 15 seconds increased the intermetallic layer thickness from ~1.7 to ~3 µm and resulted in the formation of harder stirred zone. This consequently increased the strength of the weld.