Thickness Of Intermetallic Compound Layer Research Articles

Formation and Evolution of Interfacial Structure in Al–Si–Mg/Stainless Steel Bimetals during Hot-Dipping Process

Understanding trends in the formation of the intermetallic compound (IMC) layer in Al/Fe bimetallic composites can aid in significantly improving their mechanical properties. However, it is currently challenging to predict IMC layer formation during hot-dip aluminizing. Furthermore, the results from previous studies are difficult to compare owing to the variation in the process parameters used. Therefore, to understand how temperatures and holding times affect the thickness and hardness properties of IMC layers, we investigated the interfacial properties of aluminized stainless steel in molten Al-Si-Mg. AISI 420 stainless steel was hot-dip aluminized in an Al–Si–Mg alloy melt for 10–120 min at four different temperatures: 700, 750, 800, and 850 °C. Morphology, type, and element distribution of the phases formed in the reaction layer and the reduction rate of the aluminizing process were studied. Notably, while the reaction layer thickness increased with increasing aluminizing temperature when the holding time was low, long-term reaction caused the reaction layer to become thicker at lower temperatures. The mechanism of this morphological transformation is discussed. The results demonstrated effective trends in controlling the morphology of the intermetallic compound layer with respect to various hot-dip Al plating process parameters.

High-Temperature Oxidation of the 304/6061 Welding–Brazing Joint and Its Effects on Corrosion Characteristics

Laser–MIG hybrid welding–brazing was used to weld 304 stainless steel and 6061-T6 aluminum alloy with a thickness of 2 mm. The microstructure, morphology, chemical composition and corrosion behavior of the samples after high-temperature oxidation were investigated. The results reveal that the 304/6061 dissimilar joint had a thicker intermetallic compound layer (7–8 μm) during high-temperature oxidation (HTO) treatment than the sample without HTO treatment (2–3 μm). The oxide film thickness of the 6061 side of the weld joint treated by HTO (2401 nm) increased compared to the samples (181.1 nm) without HTO treatment. Unlike other metals treated by high-temperature oxidation, the high-temperature treatment process in this paper can reduce the corrosion resistance of the base metal and dissimilar joints, and the sequence of the corrosion current density was weld (HTO) >weld>6061 (HTO) >6061>304 (HTO) >304.

Effect of material position and tool offset on the microstructure and mechanical properties of friction stir welded AA7075/AZ31B with ultrasonic assistance

The primary focus of this study is to analyze how changes in material position and tool offset affect the microstructure and mechanical properties of dissimilar alloys (AA7075/AZ31B) joints. The study specifically examines these effects in normal and ultrasonic-assisted friction stir welded (UVaFSW) aluminum and magnesium-based joints. The experiment showed that the sound weld was achieved only when the AA7075 plate was placed on the advancing side (AS). The metallographic analysis showed that the use of ultrasonic vibration increased the flow of material in the nugget zone (NZ) and improved the length of interpenetration at the interface. Moreover, the intermetallic compound (IMC) layer thickness decreased throughout the interface during UVaFSW, improving joint strength. The maximum ultimate tensile strength was obtained at 1 mm tool-off condition for UVaFSW, i.e., 112.40 ± 7.24 MPa. Ultrasonic vibrations reduced the IMC thickness by up to 78 % at the middle of the joint interface. The fracture surface showed the ductile fracture mode in the case of UVaFSW compared to the FSW process. The current study establishes the framework for optimizing and controlling the welding process of dissimilar AA7075/AZ31B alloys, which possess considerable potential for use in the aviation industry.

Improved Interface Morphology and Failure Load of Ultrasonic-Assisted Friction Stir Lap Welding Joint of 2024 Aluminum Alloy to 304 Stainless Steel

Achieving high-strength welding joint of aluminum to steel is a highly pressing and challenging task in the manufacturing industries, and friction stir lap welding (FSLW) has advantages for joining these two metals. To further heighten the strength of dissimilar aluminum and steel metals (Al/steel) FSLW joint, the ultrasonic-assisted FSLW (UAFSLW) process was used, and the upper 2024-T4 aluminum alloy and the lower 304 stainless steel were chosen as research object. The results show that the addition of ultrasound eliminates the micro pores, changes the aluminum-rich intermetallic compounds (IMCs) into the iron-rich IMCs and enhances the micro and macro mechanical interlocking structures along the Al/steel lap interface. Under the rational IMCs layer thickness lower than 1.5 μm, the UAFSLW joint has the failure load higher than the traditional FSLW joint. The maximum failure load of UAFSLW joint reaches 7.06 kN, and the loading capacity of this joint is higher than that of reported Al/steel traditional FSLW joint. The UAFSLW process is an effective way to fabricate the high-strength Al/steel lap joint.

Intermetallic compound growth behavior and mechanical performance in Sn58Bi/Cu solder joint bearing Mg particles incorporation during thermal aging

The microstructure and intermetallic compound (IMC) growth in Sn58Bi/Cu and Sn58Bi-0.4 Mg/Cu solder joints were examined in this study under varied thermal aging time (6, 12, 18, 24, and 30 h) at 120 °C. The Shear test was conducted to assess the solder joint mechanical performance. The results indicated that the precipitation of the Bi phase in Sn58Bi/Cu and Sn58Bi-0.4 Mg/Cu solder joints was not significantly inhibited by adding Mg as aging time increased. The IMC layer thickness of both solder joints increased as the aging time increased, but the Cu3Sn IMC thickness in Sn58Bi-0.4 Mg/Cu solder joint was consistently thinner than that in Sn58Bi/Cu joint. The temporal evolution of the Cu3Sn IMC layer was investigated, and it was found that the inclusion of Mg particles reduced the diffusion coefficient of Cu3Sn IMC. Furthermore, the shear test revealed that throughout the initial phases of thermal aging, fractures occurred within the solder matrix for both joints. As thermal aging time increased, fractures extended into the IMC layer, accompanied by transgranular and intergranular fractures. Simultaneously, adding Mg particles delayed brittle fracture in the solder joints, enhancing their mechanical properties.

Research on the mechanical properties and fracture mechanism of ultrasonic vibration enhanced friction stir welded aluminum/steel joint

Friction stir welding (FSW) and ultrasonic vibration enhanced friction stir welding (UVeFSW) were used to connect 3 mm thick 2024-T3 Al alloy and Q235 carbon structural steel. The weld forming quality, mechanical properties, fracture location and interface behavior of the whole and layered joints were compared and analyzed, and the different mechanisms of the ultrasonic vibration to improve the tensile strength of the joint were summarized. As the results show, the ultrasonic vibration promoted the plastic flow ability of materials and improved the welding seam forming quality. Moreover, the ultrasonic vibration made the plastic deformation of the material in the nugget zone more uniform, which improved the strength of the nugget zone. In the middle layer of the joint, the ultrasonic vibration reduced the thickness of intermetallic compound layers (IMCLs), eliminated the laminated structure that harmed the connection quality of the joint, and formed a micromechanical interlocking structure in which IMCLs was inserted into the steel, which improved the interfacial bonding strength and improved the tensile strength by 11.1%. The ultrasonic vibration optimized the macro-mechanical interlocking structure in the joints of the lower layer, which enhanced its mechanical bonding ability with Al alloy.

Crack initiation and propagation behavior of dissimilar interface with intermetallic compound layer in Al/steel joint using coupled multiscale mechanical testing

We demonstrate multiscale mechanical testing using miniature and microscale tensile tests to elucidate the crack initiation and propagation behaviors corresponding to interfacial nanostructures in dissimilar joints of 6061 aluminum alloy and 304 stainless steel. The initial nucleation and subsequent growth of intermetallic compounds (IMCs) can be controlled by heat treatment after friction stir lap welding. The miniature tensile tests exhibited the relationship between the joint strength and IMC layer thickness with changes in the fracture location. Microscale tensile testing using a single edge-notch tension geometry initiates the crack and subsequent propagations near the interface, which helps identify the crack initiation site and understand the dependence of the local strength on the type of IMCs. Crack deviation behavior toward the Al side, attributed to the difference of local strength, is confirmed by in situ observations, which indicated that continuous failure can easily occur within the grown IMCs, particularly in macroscale joints. It was concluded that the crack propagation is controlled by the local crack deviation toward metal matrix, which tends to occur for the dissimilar interface with thin IMC layer. This miniature/microscale tensile testing approach is expected to clarify the essential relationship between the interfacial microstructure and the fracture behavior.

Formation and Evolution Mechanism of Intermetallic Compounds of Friction Stir Lap Welded Steel/Aluminum Joints.

Interfacial layers with brittle intermetallic compounds (IMC) greatly influence the performance of steel-aluminum friction stir lap welding (FSLW) joints. Thus, the formation and evolution of IMC between 7075-T6 aluminum alloy and galvanized DP590 steel in steel-aluminum FSLW joints were investigated. An FSLW numerical model was developed using the computational fluid dynamics method to analyze the interface temperature between the aluminum alloy and steel. Scanning electron microscopy (SEM) was conducted to observe the microstructure characterization and measure the IMC thickness. Phases among different joint zones were analyzed by X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS). IMC layer formation was predicted by the effective Gibbs free energy model presented in this paper according to thermodynamic principles. The Monte Carlo method was utilized to predict the thickness of IMC layers. It was found that the IMC layer at the interface of the welded joint is composed of Fe2Al5, FeAl3, and Al-Zn eutectic. The IMC thickness decreased from 4.3 μm to 0.8 μm with the increasing welding speed, which was consistent with the Monte Carlo simulation results.

Kinetics of intermetallic compound layers between AISI 321 stainless steel and molten aluminum

The interfacial reaction between liquid aluminum and solid steel is critical to understanding the evolution of intermetallic compounds (IMCs) in the brazing and weld brazing processes of aluminum-to-steel dissimilar alloys. In this study, hot dip aluminizing of AISI 321 stainless steel at different temperatures was conducted to reveal the influence of reaction temperature and time on interfacial IMCs. Electron microscopy analyses were employed to investigate the interfacial microstructures. A single layer of θ-Fe4Al13 was observed at 700°C. In contrast, the IMCs of interfaces dipped at 800–1000°C consisted of a thin inner layer of η-Fe2Al5 + ζ-FeAl2 next to the steel and a thick layer of θ-Fe4Al13 close to the aluminum. For the inner layer, the thickness increased with increasing dipping temperature and time. Its growth was described by a parabolic rate law, which suggested a diffusion-controlled mechanism at the interface. An activation energy of 66.5 kJ mol−1 was obtained. For the Fe4Al13 layer, the thickness evolution at different temperatures was different from that of the inner layer, with a thick IMC layer at 700°C, a thinner IMC layer at intermediate temperatures (from 800 to 900°C), and a slightly thicker IMC layer from 950 to 1000°C. The growth kinetics of Fe4Al13 at 700°C were controlled by diffusion, interfacial reactions, and dissolution mechanisms. The evolution of Fe4Al13 between 800 and 1000°C was governed by diffusion and dissolution mechanisms. The appearance of the inner layer and the evolution kinetics of Fe4Al13 accounted for the decrease in thickness with increasing temperature between 700 and 900°C.

In Situ SEM, TEM, EBSD Characterization of Nucleation and Early Growth of Pure Fe/Pure Al Intermetallic Compounds.

The nucleation and growth processes of pure Fe/pure Al intermetallic compounds (IMCs) during heat treatment at 380 °C and 520 °C were observed through in situ scanning electron microscopy (SEM). The size of the IMCs were statistically analyzed using image analysis software. The types and distribution of IMCs were characterized using transmission electron microscopy (TEM) and electron backscattering diffraction (EBSD). The results showed that: at 380 °C, the primary phase of the Fe/Al composite intermetallic compounds was Fe4Al13, formed on the Fe side and habituated with Fe. The IMC was completely transformed from the initial Fe4Al13 to the most stable Fe2Al5, and the Fe2Al5 was the habitus with Fe during the process of holding at 380 °C for 15 min to 60 min. At 380 °C, the initial growth rate of the IMC was controlled by reaction, and the growth rate of the thickness and horizontal dimensions was basically the same as 0.02-0.17 μm/min. When the IMC layer thickness reached 4.5 μm, the growth rate of the thickness changed from reaction control to diffusion control and decreased to 0.007 μm/min. After heat treatment at 520 °C (≤20 min), the growth of IMC was still controlled by the reaction, the horizontal growth rate was 0.53 μm/min, the thickness growth rate was 0.23 μm/min, and the main phase of the IMC was the Fe2Al5 phase at 520 °C/20 min.

Fatigue performance and microstructure of lead-free solder joints in BGA assembly at room temperature

One of the crucial factors in evaluating the reliability of an electronic appliance is fatigue failure of the interconnecting solder joints. In most situations, large bulk samples are used to investigate the fatigue characteristics of the solder materials. Only a few studies have examined the solder joints frequently observed in ball grid array (BGA) components. This study implemented a specialized test vehicle in BGA assembly connecting two substrates with nine identical solder joints. Four SAC-based solder alloys were tested using an Instron micromechanical tester in the stress-controlled and strain-controlled methods at room temperature and constant strain rate. At two distinctive stress and strain levels, the fatigue performance of alloys featuring organic solderability preservative (OSP) and electroless nickel-immersion gold (ENIG) surface finishes was investigated. The fatigue results obtained from the stress-controlled and strain-controlled tests were compared. Microstructural analysis was performed using scanning Electron Microscopy (SEM) and energy dispersive spectroscopy (EDS) to identify the precipitates in the bulk solder and the morphologies of IMC layers. The thickness of intermetallic compound (IMC) layers and the failure mode were examined in each case. The results demonstrated that the OSP surface finish significantly outperformed the ENIG surface finish regardless of the testing process and solder alloy. Various failure modes were observed, depending on the solder alloy and IMC layer.

Effect of the addition of CeO2 nanoparticles on the microstructure and shear properties of Sn–57Bi–1Ag solder alloy

In this study, different weight fractions (0, 0.2, 0.5, 0.7, and 1.0 wt%) of cerium oxide (CeO2) nanoparticles were used to enhance the properties of Sn–58Bi–1Ag (SBA) solder alloys. As expected in the design, the CeO2 nanoparticles are diffusely distributed in the solder matrix. The microstructure evolution, growth of intermetallic compound (IMC) at the interface, and shear properties of the composite solder were systematically investigated using a scanning electron microscope (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS) and electron backscatter diffraction (EBSD) probes. The results showed that adding an appropriate amount of CeO2 nanoparticles can refine the microstructure of the composite solder. Many β-Sn twin structures were observed in the SBA-0.5CeO2 and SBA-0.7CeO2 solder matrix, bringing better deformability to the β-Sn phase and improving the plasticity of the solder matrix. Moreover, with the addition of nanomaterials, there was a notable decrease in the thickness of the interfacial IMC layer of the solder/Cu joint, accompanied by a refinement in the grain size of the IMC. To our satisfaction, the addition of CeO2 nanoparticles in the appropriate proportion exhibited a remarkable enhancement in both shear strength and toughness of the composite solder alloys, working in tandem to transform the fracture mechanism from a purely brittle mode to a mixed mode of ductility and brittleness. It is indicated that the doping of CeO2 improves the reliability of SBA solder, potentially paving the way for a novel approach to particle-enhanced modification of Sn–Bi–Ag-based low-temperature solders.

Effect of post-weld heat treatment on the microstructure and properties of titanium/304 stainless steel laser welding dissimilar metal joints with copper as the transition layer

Low elongation has been an important factor limiting the application of titanium/304 stainless steel (304SS) laser welding of dissimilar metal joint products. By adopting the post-weld heat treatment (PWHT) process of holding the welded joint at 400 ℃, 550 ℃ and 700 ℃ for 30 min, this study increases the elongation of the welded joint from 0.3 % to 2.21 % in the welded state and further analyses and investigates the structural changes in the organization and the formation process of intermetallic compounds (IMC) within the weld seam. The results showed that the acicular structure in the weld could not be eliminated by holding at 400 ℃ for 30 min, but only part of the residual stress was released, and the elongation was increased to 0.85 %. After holding at 550 ℃ for 30 min, a large number of equiaxed crystals appeared to replace the acicular structure in the weld and released the residual stress. With the enhancement of the IMC layer thickness, grain gap and deformation coordination ability, the elongation increased to 2.21 %. After holding at 700 ℃ for half an hour, the IMC layer becomes thinner, the grain gap decreases, the deformation coordination ability deteriorates, and the tensile strength and elongation decrease. In the tensile test, the fracture position was all at the weld. After being held at 400 ℃ for 30 min, the average tensile strength of the tensile sample increased from 330 MPa in the welded state to 352 MPa; after being held at 550 ℃ for 30 min, the average tensile strength of the tensile sample was 340 MPa, and the fracture elongation was 7.4 times that of the welded state, reaching 331 µm.

Study on the metallurgical reaction law and mechanism of the Ni-xCu alloys/pure Sn solid-liquid interface

In this study, Ni-xCu alloy substrates/pure Sn soldering joints were prepared, and the metallurgical reaction law and mechanism of the Ni-xCu/Sn solid-liquid interface were studied based on electron probe microanalyzer (EPMA) and electron backscatter diffraction (EBSD). Results showed that with the increase of Cu content in the Ni-xCu alloys, the reactants at the Ni-xCu/Sn interface changed from (Ni,Cu)3Sn4 single phase (x ≤ 40 wt%) to (Ni,Cu)3Sn4 and (Cu,Ni)6Sn5 two phases (50 wt% ≤ x ≤ 60 wt%), and then transformed into (Cu,Ni)6Sn5 single phase (70 wt% ≤ x). Correspondingly, the thickness of the intermetallic compound (IMC) layer presented four stages: decreased slowly, increased slightly, increased significantly and decreased sharply. The evolution mechanism of the phase structure was clarified according to the critical Cu concentration theory for (Cu,Ni)6Sn5 phase growth. In addition, the evolution mechanism of the IMC layer thickness was explained based on the studies of (Ni,Cu)3Sn4 growth thermodynamics and (Cu,Ni)6Sn5 lattice antiphase boundary array.

Study on the dual inhibition behavior of interfacial IMCs in Cu/SAC105/Cu joint by adopting SiC nanowires and nanocrystalline Cu substrate

To obtain high-strength joints suitable for three-dimensional (3D) packaging, SiC nanowires (NWs) were doped to the Sn1.0Ag0.5Cu (SAC105) solder, and the conventional Cu substrate was replaced with nanocrystalline (NC) Cu to form Cu/solder/NC Cu solder joints. It was found that the application of SiC NWs and NC Cu had an essential effect on the evolution and growth kinetics of the solder joint interface. The formation of intermetallic compounds (IMC) bridging and full-IMC joints at the interface was delayed. The absorption effect of SiC NWs and numerous nucleation sites provided by NC Cu resulted in a notable reduction in interfacial IMC grains size and interfacial Cu3Sn IMC layer thickness. In addition, the Cu/SAC105-SiC/NC Cu solder joint exhibited the highest shear strength. On the one hand, SiC NWs were incorporated into Cu6Sn5 IMC grains to form the reinforced concrete structure. On the other hand, NC Cu provided more fine Cu6Sn5 IMC grains for the interface. Combined with the analysis of the fracture morphology, it can be concluded that the combination of SiC NWs and NC Cu substrate substantially improved the mechanical properties of the solder joints.

Wetting kinetics, spreading phenomena and interfacial reaction of Sn-15Bi-xZn solders on Cu substrate at different temperatures

PurposeThis study aims to analyze the wettability of the self-developed Sn–Bi–Zn solder and to conduct a series of analysis on the wetting kinetics, diffusion phenomenon and interfacial reaction of Sn–Bi–Zn solder on Cu substrate.Design/methodology/approachThe wetting kinetics, diffusion phenomenon and interfacial reaction of Sn–Bi–Zn solder on Cu substrate were analyzed by experiments. The interface was observed by scanning electron microscope to study the effect of Zn content on its interface.FindingsWith the increase in brazing temperature, the final spreading equivalent radius of the solder increases significantly, and the final contact angle of the solder decreases significantly. In addition, when the Zn content is 1%, the spreading effect of solder is the best, the equivalent radius is the largest and the contact angle is the smallest. According to the microstructural analysis, the thick intermetallic compounds layer of the Sn–15Bi–xZn solders on the Cu substrate can be effectively decreased by adding appropriate Zn content.Originality/valueThe wetting kinetics, diffusion phenomenon and interfacial reaction of Sn–15Bi–xZn solder on Cu substrate at different temperatures have not been studied yet.

Dissimilar Friction Stir Joining of Aluminum Alloy and Stainless Steel: A Study on the Intermetallic Compound Formation, Microstructure, and Mechanical Properties of the Joints

Abstract This study employed the friction stir welding technique to find the optimal tool traverse speed for successfully joining the 304 stainless steel with 6061-T6 aluminum alloy. For this purpose, five different traverse speeds at a constant rotational speed of 875 rpm were considered. The welded joints were characterized based on the mechanical properties, micro/macrographs, and quantification of steel fragments and intermetallic compounds (IMCs) inside the stir zone (SZ). The composition and phase of the IMCs at the interface, SZ, and intercalated structure were confirmed through X-ray diffraction analysis, energy-dispersive X-ray spectroscopy, field emission scanning electron microscope, and atomic force microscope. It is observed that the traverse speed of 90 mm/min produced the highest tensile strength with an IMC layer thickness of 1.47 ± 0.23 μm. At this traverse speed, the area fraction of IMCs and steel fragments is around 0.023 % and 6.05 % of the SZ area, respectively. Furthermore, the defects increased by reducing the traverse speed from 90 to 30 mm/min because of a higher fraction of IMCs (i.e., Al3Fe) and steel fragments inside the SZ. The traverse speed higher than 90 mm/min generated the cracks at the interface because of insufficient stirring at low heat input. The hardness improved by decreasing the traverse speed because of grain refinement in SZ and thermomechanically affected zone. The intercalated structure acted as the hardest zone because of the formation of IMCs, namely Al3Fe + AlFe at 30–70 mm/min, and Al3Fe + AlFe + AlFe3 at 90 and 120 mm/min.

Interfacial intermetallic compound layer in friction stir welded Mg/Al joints: Relationship between thickness and the welding temperature history

Thickness of the intermetallic compounds (IMC) layer at the interface has a significant effect on the mechanical properties of Mg/Al dissimilar joints. However, the thickness of IMC layer can be only obtained by metallurgical microscopy, which is destructive and has to break down the weld. Therefore, it is crucial to find a reliable approach that can non-destructively predict the thickness of IMC layer in practical application. In the current study, Mg alloy and Al alloy were friction stir butt welded (FSW) under different tool rotation speeds (TRS) to obtain different thicknesses of IMC layers. As the TRS increased from 400 rpm to 1000 rpm, thickness of the IMC layer increased from 0.4 μm to 1.3 μm, the peak welding temperatures increased from 259 °C to 402 °C, and the Z-axis downforces decreased from 10.5 kN to 3.2 kN during welding process. Higher TRS would generally induce higher welding heat input, which promotes the growth of the IMC layer and the softening of base materials. The IMC layer formed through solid-state diffusion and transformation instead of eutectic reaction according to the welding temperature history and interfacial microstructure, and its evolution process was clearly observed by plan view. In order to incorporate the effect of dramatic change of welding temperature which is the characteristic feature of FSW, PsdVoigt function was used to fit the welding temperature histories. A new prediction formula was then established to predict thicknesses of IMC layers with considering sharp welding temperature change. Predicted thicknesses gave good agreement with measured thicknesses obtained experimentally under different welding parameters, which confirmed the accuracy and reliability of the new prediction formula. Based on this prediction formula, the time period of temperature higher than 200 °C during welding was found critical for the thickening of interfacial IMC layers.

Mechanical performance of dissimilar friction stir welded lap-joint between aluminium alloy 6061 and 316 stainless steel

The dissimilar lap-joint of the AA6061 to 316 stainless steel was produced by friction stir welding. Changing microstructure, joint interface, and mechanical performances via welding rate were revealed. A wave interface pattern was found at the low welding rate with a free oxide layer. The interface became flat at the high welding rate with the oxide film formation. The diffusion and intermetallic compounds (IMCs) layers were formed on the interface and their thickness decreased via increasing the welding rate. The highest joint strength was obtained at the welding rate of 75 mm/min but strongly reduced with growing the welding rate. The strength was dramatically correlated with the bonding area, diffusion thickness and interface morphology instead of the IMCs layer thickness. At the low welding rate, the joint was fractured via ductile behaviour with a lot of dimples found on the fracture surface of 316 stainless steel.

Drastic Improvement in Dissimilar Aluminum-to-Steel Joint Strength by Combining Positive Roles of Silicon and Nickel Additions

Dissimilar welding of an aluminum (Al) alloy to steel is expected to be effective for weight reduction of automotive car bodies. In this study, an aluminum alloy 1050 sheet was welded to a nickel (Ni)-plated Fe sheet using a silicon (Si)-containing Al filler by gas tungsten arc welding. The effect of the simultaneous addition of Si and Ni on the Al/Fe joint strength associated with the microstructure of the intermetallic compound (IMC) layer was systematically examined. The addition of Si and Ni individually improved the Al/Fe joint strength by the reduction in the IMC layer thickness caused by the Si addition and the refinement of the IMC grains due to the Ni addition, respectively. The most effective improvement in the joint strength was achieved by the simultaneous addition of Si and Ni. The IMC layer at the Al/Fe interface with Si addition consisted of θ-Fe4Al13, η-Fe2Al5, and Al–Fe–Si ternary IMCs, while it changed to θ-Fe4Al13, η-Fe2Al5, and an Al–Fe–Ni ternary IMC after Ni was additionally added. This change in the phase as well as the thickness reduction and grain refinement of the IMC layer probably contributes to further improving the joint strength by the simultaneous addition of Si and Ni.