Formation 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.

The growth behavior and kinetics of intermetallic compounds in Cu–Al interface at 600°C–800 °C

Due to the low production cost and light weight, copper-clad aluminum conductors show great potential value in the field of power transmission, while the phase structure and organizational changes at the Cu–Al interface in high-temperature environments have a great impact on the electrical and mechanical properties. In this paper, Cu–Al diffusion couples are prepared to study the diffusion process, microstructure, and growth kinetics of intermetallic compounds (IMCs) in Cu–Al interface during heating from 600 °C to 800 °C, and the mechanical and electrical properties of Cu–Al diffusion couples are discussed. The results show that after heat treatment, IMC layers are formed at the Cu–Al interface and the Al-side is composed of CuAl and CuAl2, in which the CuAl phase transforms from long to thick dendrites with the increase of temperature, and finally grows into a “popcorn” form. The IMCs at the Cu–Al interface from the Cu side to the Al side are in the order of Cu3Al layer, Cu9Al4 layer, Cu3Al2 layer and CuAl layer, among which the Cu3Al2 layer is the thickest (168.42 μm at 700 °C), while the Cu3Al layer is the thinnest (37.32 μm at 700 °C). The kinetic calculations show that the diffusion layer grows up rapidly, which is caused by the generation of liquid-phase during the heating process, leading to the acceleration of the diffusion of Cu and Al. The kinetic factor of the Cu3Al2 layer is the largest (n = 0.69), causing the fastest growth rate of the Cu3Al2 layer, while the Cu3Al layer shows the largest activation energy for diffusion and the smallest diffusion rate (Q = 9.48 kJ/mol, D0 = 2.06 × 10−1 m2/s), therefore its growth rate is the slowest. Based on the thermodynamic calculations and the Cu–Al phase diagram, a growth mechanism of the Cu–Al interface is proposed, the formation sequence of IMCs at the Cu–Al interface is Cu9Al4, CuAl, Cu3Al2 and Cu3Al. The formation of IMCs layer at the Cu–Al interface leads to a significant increase in the hardness of Cu–Al samples (the hardness of the Cu3Al2 is 10 times higher than that of Cu) and an obvious decrease in electrical conductivity (the electrical resistivity of Cu–Al is 5 orders of magnitude higher than that of Cu), affecting its application in the electrical industry.

Corrosion mechanism of reduced activation ferritic martensitic steel JLF-1 in liquid metal Sn

Reduced activation ferritic martensitic steel JLF-1 (Fe-9Cr-2 W-0.1 C) corroded in liquid Sn at 673–873 K due to the formation of intermetallic compound layers. The outward growth of FeSn2 layer at 773 K was rate-controlled by a boundary diffusion. The inward growth of FeSn-like layer was recognized in the exposure for more than 250 h. The FeSn growth progressed according to the diffusion of Sn along the boundaries of martensite structure. Thin Cr2O3 layer formed by a pre-oxidation treatment did not function as an anti-corrosion layer in liquid Sn, though the sintered specimens of Fe2O3 and Cr2O3 revealed corrosion resistance.

Influence of Fly Ash Geopolymer Ceramic Powder Addition on Sn-3.0Ag-0.5Cu Solder Joints

This paper reports the effect of 1.0 wt.% fly ash (FA) geopolymer ceramic powder addition in Sn-3.0Ag-0.5Cu (SAC305, in wt.%) solder joint. Powder metallurgy route was used to fabricate the new composite solder. Solder balls were formed from the new composite solder and reflowed on Cu substrate. The effect of FA as ceramic reinforcement on the bulk microstructure and the interfacial intermetallic compound layer formation of solder joints were investigated under optical microscope. Microstructure observation showed that the β-Sn dendrite size was refined in SAC305-1.0FA/Cu bulk solder joint sample than that in the non-reinforced sample. The addition of FA geopolymer ceramic powder into the solder matrix also produced a thinner intermetallic compound layer.

Effect of tool travel speed on tensile strength of friction stir welded dissimilar joint of aluminium AA6061 T6 alloy and maraging M250 steel

Friction stir welding (FSW) is a promising welding method to produce dissimilar joints between steel and aluminium. The formation of the intermetallic compound layer at the dissimilar joint interface affects the joint mechanical properties, which are also influenced by the FSW process parameters. In the present research work, M250 Maraging steel and AA6061 T6 aluminium alloy were joined by FSW. The joints were prepared with five different tool travel speeds ranging from 0.33 mm s−1 to 1 mm s−1 using a tapered tool pin made by tungsten carbide material, keeping tool rotational speed constant. The welded joints were analyzed for their tensile behaviour and microstructural change, including hardness measurement. The failed samples are analyzed using a scanning electron microscopy device for their mode of failure. In the Energy Dispersive X-Ray Spectroscopy (EDS) analysis, the formation of intermetallic compound (IMC) layers of Fe3Al, Fe4Al13, and Fe2Al5 are observed. When the thickness of the IMC layer increases, the joint strength decreases. It is found that the welding speed influences the thickness of the IMC layer formed, causing variation in the strength of the dissimilar joint. Better joint efficiency is obtained at a tool travel speed of 0.67 mm s−1.

Effect of bonding temperature on the microstructure and mechanical properties of the diffusion-bonded joints of Zr705 alloy

Research on the diffusion bonding of ( )similar joints of zirconium (Zr) alloys is limited as compared to that on the diffusion bonding of ( )dissimilar joints. The similar Zr alloys are difficult to bond together owing to its high melting point; however, an added interlayer can solve this problem. This study demonstrated the successful vacuum diffusion bonding of the Zr-2.5Nb (Zr705) alloy with a Cu interlayer at 900–960 °C and analyzes the microstructure and mechanical properties of the diffusion-bonded joints. The layered morphology of the joints at 900 °C and 920 °C is attributable to the formation of intermetallic compound layers ( ). In contrast, no such formation was observed at 940 °C and 960 °C owing to the complete diffusion of Cu atoms into the Zr substrate. The base material at the bonding temperatures of 900 °C and 920 °C exhibited two different microstructures i.e., a Widmanstätten microstructure near the bonding interface and a duplex microstructure away from the bonding interface. However, the temperatures at 940 °C and 960 °C exhibited an entirely Widmanstätten microstructure. The tensile strength of the joints increased with the bonding temperature, from 78 MPa at 900 °C to a maximum of 603 MPa at 960 °C (joint efficiency = 104.8%), and the elongation first increased and then decreased with the increasing temperature; at 940 °C, it reached 54% that of the original Zr705 alloy.

Process of welding-brazing and interface analysis of lap joint Ti-6Al-4V and aluminum by plasma arc welding

The difference of physical properties of Ti-6Al-4V alloy/aluminum dissimilar metals and the formation of intermetallic compound layer at the joint interface limit their reliable connection. The connection of Ti-6Al-4V alloy/aluminum was realized by plasma arc welding with lap joints of Ti-6Al-4V alloy plate on the top of aluminum. By changing the welding offset and current, a good welding joint can be obtained. The microstructure and mechanical properties of the joint were analyzed by optical microscope, scanning electron microscope (SEM), X-ray diffraction (XRD) and tensile test. Finally, the thermal process of the joint under different parameters was compared with the test, and the formation mechanism of the interface was discussed. The results show that the microstructure of the joint shows that the Ti-6Al-4V alloy is partially melted, and there is an unfused area, which is melted by heat conduction to the lower aluminum base metal, thus realizing metallurgical bonding. The interface transition layer is mainly the diffusion between titanium and aluminum atoms, and a lamellar TiAl3 intermetallic compound layer is formed on the aluminum side with a thickness of about 1 μm. The specimen is fractured on the side of aluminum base metal with the maximum load of 1.76 kN. The joint shows good mechanical properties. The results of finite element thermal analysis of the fusion zone of Ti-6Al-4V alloy and aluminum has good correspondence with the experimental results. When the current value increases, the weld center temperature and the size of the fusion area show an increasing trend. When the current value is 70A and the offset is 3 mm, it is conducive to the formation of good welded joint.

Principle for obtaining high joint quality in dissimilar friction welding of Ti-6Al-4V alloy and SUS316L stainless steel

Ti-6Al-4V alloy (Ti64) and SUS316L stainless steel rods were dissimilarly friction welded. Especially focusing on the detailed observation of interface microstructural evolution during the friction welding (FW), the relationship between the processing conditions, weld interface microstructure, and mechanical properties of the obtained joints were systematically investigated to elucidate the principle for obtaining a high joint quality in the FW of Ti64 and SUS316L. A higher friction pressure produced a lower welding temperature in the FW, hence suppressing the thick intermetallic compound layer formation. However, hard and brittle Ti64/SUS316L mechanically mixed layers generally formed especially at the weld interface periphery due to the high temperature increasing rate, high rotation linear velocity and high outward flow velocity of the Ti64. These harmful layers tended to induce the cracks/voids formation at the weld interfaces hence deteriorating the joints’ mechanical properties. The rotation speed reduction and liquid CO2 cooling during the entire processing decreased the temperature increasing rate, rotation linear velocity and outward flow velocity of the Ti64 at the weld interface periphery. Therefore, they suppressed the formation of the harmful mechanically mixed layers, facilitated the homogeneous and sound interface microstructure generation, and finally produced a high-quality dissimilar joint in the FW of Ti64 and SUS316L.

Study of intermetallic compound (IMC) formed in welding of steel with magnesium: A review

The welding of steel and magnesium as a dissimilar welding is most important manufacturing process for industrial point of views. Both the materials have their unique properties and therefore, used on specific application. The joining to steel and magnesium can be done by some specific welding techniques. Due to dissimilar alloys welding, some intermetallic compound forms during the welding. The present paper reviews the formation of IMC layer on the welding of Fe with Mg using TEM images. The welding of Fe with Mg is done with DC resistance spot welding and butt fusion welding as the welding processes. The effects of the interlayer formed by the two different welding processes are discussed in details. From the TEM images of DC resistance spot welding, it is clear from the TEM analysis that the IMC play a crucial role for the strengthening of joint.

Influence of interface structure and stress distribution on fracture and mechanical performance of STS439/Al1050/STS304 clad composite

STS439/Al1050/STS304 clad composite with high specific strength and high bending resistance was processed and its formability and interface fracture behavior of as-roll-bonded and annealed clad composite were studied. To predict the interface strength and the contact shear stress at the point of interface fracture, the finite element method (FEM) was carried out using ABAQUS. Post-roll-bonding annealing at 550 °C induced the formation of intermetallic compound layer both at STS439/Al1050 and Al1050/STS304 interfaces. Micro-voids, detrimental to the interface bonding strength, were observed after annealing at the interface between the intermetallic compounds and Al1050 due to the faster diffusion of Al in comparison to Fe. Interface separation and fracture occurred at the interface between STS439 and Al1050 irrespective of loading conditions in the annealed clad composite, resulting in the rapid load drop. The closer proximity of STS439/Al1050 to the neutral axis than the STS304/Al1050 interface induces greater shear stress and preferential interface cracking along the STS439/Al1050 interface. The contact shear stress as-rolled clad composite were predicted to be 241 MPa and 308 MPa without interface failure for conditions A (STS304 side in tension) and B (STS439 side in tension) using FEM, suggesting interface bonding strength after roll-bonding is greater than 308 MPa. The maximum contact shear stress predicted by FEM simulation at the point of interface cracking of the clad composite annealed at 550 °C for 12 h dropped appreciably to 125 MPa and 111 MPa for conditions A and B, respectively. The contact shear stresses further decreased to 85 MPa and 67 MPa for conditions A and B, respectively, with increase of annealing duration to 24 h.

Effect of ultrasonic vibration on the intermetallic compound layer formation in Al/Cu friction stir weld joints

Dissimilar aluminium alloy and pure copper joints were produced using a novel ultrasonic vibration assisted friction stir welding (UVaFSW) assembly. The intermetallic compounds (IMCs) formed at the Al-Cu interfaces were characterized using a scanning electron microscope and energy-dispersive X-ray spectroscopy analysis. The thermodynamic prediction of the first intermetallic compound formation using effective Gibbs free energy change of formation (EGFEF) model was used to calculate the first intermetallic compound layer to nucleate or form during each process condition at the joint interface. The results show that irrespective of the welding conditions (with and without ultrasonic vibrations) intermetallic compounds are formed at the interface. However, the ultrasonic vibration effectively reduced the thickness of the IMC layer at the joint interface and consequently improved the mechanical properties of the joints.

Design of laser welding applied to T joints between steel and aluminium

Laser conduction welding was used to directly join DH36 steel to AA5083 aluminium alloy in a T joint configuration, each plate with 6 mm of thickness. The effect of the process energy (via power density and interaction time) on the joint integrity and quality in terms of cracking, porosity and intermetallic compound layer formation was investigated. Successful T joints were produced by melting of the aluminium plate, which was inserted into a 4 mm deep groove machined on the steel plate, with the heat generated by the laser irradiation on the steel surface. The IMC layer thickness was less than 5 μm. Although cracking was observed along the IMC layer with higher levels of energies, the joints were still strong due to the mechanical inter-locking effect resulting from the novel design of the component, whereby the IMCs were subjected to compressive state of stress while loading.

Intermetallic compounds (IMCs) formation during dissimilar friction-stir welding of AA5005 aluminum alloy to St-52 steel: numerical modeling and experimental study

In this research, AA5005-O aluminum-magnesium alloy and St-52 low carbon steel sheets were friction-stir welded in a butt-dissimilar joint design. Effects of different processing parameters including tool rotational speed (w), traverse velocity (v), plunge depth, and offset distance on the solid-state weldability of these dissimilar materials were assessed in terms of formation of intermetallic compound (IMC) layer at the interface. A 3D thermo-mechanical finite element modeling procedure was employed to predict the nucleation and growth of IMC layer. Formation of various FeAl, FeAl3, and Fe2Al5 IMCs at the interface, layer morphology, and thickness were experimentally studied as well, by using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) analysis techniques. A good agreement between the simulated thermal results and experimental data was noticed. The results showed that the thickness of IMC layer at the interface as the main controlling parameter in transverse tensile property and fracture behavior of produced dissimilar joints can be varied extremely as a function of processing parameters. By decreasing the heat input and suppressing the kinetics of IMCs layer formation, the tensile performance of dissimilar welded joints is improved, considerably. However, the soundness of these dissimilar welds played another main role as a restriction mechanism against this trend. The maximum joining efficiency is attained around 90% at an optimized working window of w = 1200 rpm, v = 90 mm/min, and a plunge depth of 0.3 mm with an offset distance of 0.5 mm toward the Al side. The hardness of this optimized dissimilar weld is enhanced even more than the steel base metal caused by the formation of IMC layer at the interface as well as the dispersion of reinforcing intermetallic particles (IMPs).

Effects of Intermetallic Compound Formation in Al/Cu Clad Material Fabricated by Differential Speed Rolling.

In this study, the microstructure and mechanical property of Al/Cu clad material fabricated by differential speed rolling at room temperature were evaluated. Al and Cu plates were prepared and mechanically cladded at a differential speed ratio of 2:1 between the upper and lower rolls. Post- heat-treatment was carried out after the mechanical cladding at 400 °C for 60 min to induce the formation of intermetallic compound layers at the bonded interface of Al/Cu. As a result, differential speed rolling afforded a soundly cladded interface without any defects such as voids and cracks. In addition, intermetallic compound layers such as Al4Cu9 and Al2Cu were formed at the mechanically bonded interface during post-heat-treatment for 60 min, which led to an increase in Vickers microhardness value more than 30% relative to the base material. Therefore, we systematically explained the relationship between formation of intermetallic compounds and mechanical property of Al/Cu clad materials in this study.

Microstructure, wetting characteristics and hardness of tin-bismuth-silver (Sn–Bi–Ag) solders on silver (Ag)-surface finished copper (Cu) substrates

This paper investigates the growth behavior, morphology of intermetallic compound (IMC) layer and hardness of low melting temperature Sn–35Bi–1Ag (wt%) solders on different surface-finished Cu substrates i.e., immersion Ag (ImAg)-plated Cu and Ag/Ni-plated Cu substrates. From SEM observation, a scallop-shaped Cu6Sn5 IMC layer was found to adhere at initial reaction stage on Sn–Bi–Ag solders/ImAg-plated Cu substrate system. However, a very thin Cu3Sn IMC layer was clearly also observed between the Cu6Sn5 IMC layer and substrate after a lengthy reaction. On the other hand, in Sn–Bi–Ag solder and Ag/Ni-plated Cu substrate system, a scallop-shaped Ni3Sn4 IMC layer was observed at the interface without any Cu3Sn IMC layer formation. These IMC layers thicknesses were increased with increasing the reaction time and temperature. However, the growth behavior of Ni3Sn4 IMC layer was slower than that of Cu6Sn5 and Cu3Sn IMC layers. In solder ball regions, bright contrast Bi and needle-shaped Ag3Sn phases were clearly observed in the dark contrast β-Sn matrix in both type of solder systems. Furthermore, bright contrast Bi phase size was increased with the reaction time. However, in the Sn–35Bi–1Ag solder and Ag/Ni-plated Cu substrate system, the Bi phase appeared with fine microstructure as compared with the Sn–35Bi–1Ag solder/ImAg-plated Cu substrate system because the Ag layer dissolved into the molten solder and changed the diffusivity and chemical affinity. The hardness values of Sn–Bi–Ag solder joints on ImAg-plated Cu and Ag/Ni-plated Cu substrates after 5 min reaction at 230 °C were about 23.0 and 24.1 HV, respectively—and about 18.9 and 20.4 HV after 30 min reaction at 230 °C, respectively.

Effect of type of thermo-mechanical excursion on growth of interfacial intermetallic compounds in Cu/Sn-Ag-Cu solder joints

This study reports the effect of different types of thermo-mechanical excursion (TME) on growth of intermetallic compound (IMC) layer formed at the interface of Sn-3.0%Ag-0.5%Cu solder and Cu substrate. 1mm thick solder joints were prepared by reflowing at 270°C for either 60 or 90s. Solder joints were then exposed to one of the following TME: (i) isothermal aging at 60°C for 48, 96 and 144h, (ii) thermal cycling between −25 and 125°C for 100, 200 and 400cycles, and (iii) thermo-mechanical cycling between −25 and 125°C for 100, 200 and 400cycles, wherein a shear strain of 10% per cycle was imposed on the joint. Finite element analysis (FEA) was performed to ascertain the effects of imposed shear strain and volumetric expansion due to the formation of IMC on the stress field in the solder joint. Irrespective of the type of TME, the thickness of the IMC layer increased with time. However, IMC thickness increased relatively more rapidly under thermo-mechanical cycling condition, indicating strain enhanced coarsening of the interfacial IMC layer. FEA showed that high stresses were generated in the IMC layer and near solder-IMC interface due to the formation of IMC layer as well as imposed external strain, which might then not only enhance the IMC growth kinetics, but also affect the morphology of the IMC layer.

Effects of filling material and laser power on the formation of intermetallic compounds during laser-assisted friction stir butt welding of steel and aluminum alloys

In this paper, two kinds of materials, Ni and Zn, are selected as filling material during laser-assisted friction stir butt welding of Q235 steel and 6061-T6 aluminum alloy, and their influences on the formation of intermetallic compounds on the steel/aluminum interface of the joints were first studied. SEM was used to analyze the profile of the intermetallic compound layer and the fractography of tensile fracture surfaces. In addition, EDS was applied to investigate the types of the intermetallic compounds. The results indicate that a thin iron-abundant intermetallic compound layer forms and ductile fracture mode occurs when Ni is added, but a thick aluminum-abundant intermetallic compound layer generates and brittle fracture mode occurs when Zn is added. So the tensile strength of the welds with Ni as filling material is greater than that with Zn as filling material. Besides, the effect of laser power on the formation of intermetallic compound layer when Ni is added was investigated. The preheated temperature field produced by laser beam in the cross section of workpiece was calculated, and the tensile strength of the joints at different laser powers was tested. Results show that only when suitable laser power is adopted, can suitable preheating temperature of the steel reach, then can thin intermetallic compound layer form and high tensile strength of the joints reach. Either excessive or insufficient laser power will reduce the tensile strength of the joints.

Interfacial Reaction Analysis of Cu-Sn-Ni-P/Cu Joint Using Microwave Hybrid Heating

Microwave hybrid heating (MHH) technique was used to investigate the formation of intermetallic compound layer at Cu-7.0Ni-9.3Sn-6.3P/Cu interface. Two different susceptor materials; graphite and silicon carbide were used to provide initial heating of the filler alloy before it starts couple with the microwaves and melted on the Cu surface. The interface of IMC layer was characterized using Scanning Electron Microscope (SEM), energy dispersive X-ray spectrometry (EDS) and microhardness. Metallurgical study showed the formation of the IMC layer with multiphase at the joint interface for microwave heating of both susceptor materials. The thickness of IMC layer heating in silicon carbide susceptor was three times thinner than heating in graphite susceptor; 16.5 μm and 50.5 μm, respectively. The findings showed that microwave hybrid heating can be used to join Cu-7.0Ni-9.3Sn-6.3P/Cu and controlled the thickness of IMC layer.

Effect of SiC Particles Addition on the Wettability and Intermetallic Compound Layer Formation of Sn-Cu-Ni (SN100C) Solder Paste

The effects of SiC on wettability and intermetallic compound (IMC) formation of Sn-Cu-Ni solder paste composite were systematically investigated. Lead-free solder paste composite was produced by mixing silicon carbide (SiC) particle with Sn-Cu-Ni (SN100C) solder paste. The wettability of composite solder was studied by observing the contact angle between solder and copper substrate. The IMC phase formation on copper substrate interface was identified using X-ray diffraction (XRD). The phase as detected in the composite solder is Cu6Sn5.The wettability of composite solder was observed through contact angle between solder and copper substrate and Sn-Cu-Ni + 1.0 wt.% SiC shows improvements in wetting angle and suppresses the IMCs formation.

Preparation of Cu2Sn3S7 Thin‐Film Using a Three‐Step Bake‐Sulfurization‐Sintering Process and Film Characterization

Cu2Sn3S7 (CTS) can be used as the light absorbing layer for thin‐film solar cells due to its good optical properties. In this research, the powder, baking, sulfur, and sintering (PBSS) process was used instead of vacuum sputtering or electrochemical preparation to form CTS. During sintering, Cu and Sn powders mixed in stoichiometric ratio were coated to form the thin‐film precursor. It was sulfurized in a sulfur atmosphere to form CTS. The CTS film metallurgy mechanism was investigated. After sintering at 500°C, the thin film formed the Cu2Sn3S7 phase and no impurity phase, improving its energy band gap. The interface of CTS film is continuous and the formation of intermetallic compound layer can increase the carrier concentration and mobility. Therefore, PBSS process prepared CTS can potentially be used as a solar cell absorption layer.