Formation Of Intermetallic Layer Research Articles

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.

High-frequency linear friction welding of aluminum alloys to stainless steel

Joining of 5083 and 6063 aluminum alloys to 304 stainless steel was successfully achieved by high-frequency linear friction welding working at 245 Hz with varied friction pressure and time, which affect the heat input. Increasing the friction pressure and friction time resulted in the softening of aluminum alloys, which facilitated plastic flow and subsequent squeezing behavior. The morphology of the intermetallic compound layer, dependent on the plastic flow, determined the performance of 5083 aluminum alloy/steel joints. Excessive friction pressure and time led to inefficient welding in 6063 aluminum alloy/steel joints because the softening and squeezing behavior of the heat-treatable alloy was susceptible to the heat input. Highly efficient joints were obtained in a short duration, i.e., 1 s, through the formation of a thin intermetallic compound layer at the interface below 500 and 50 nm for 5083 and 6063 aluminum alloy/steel joints by controlling the appropriate friction pressure. High-frequency linear friction welding was demonstrated to be effective for the sound joining of various materials by controlling the friction pressure.

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.

Intereaction and intermetallic phase formation between aluminum and stainless steel

Abstract The formation of intermetallic layers in reaction between 430 StainlessSteel and Al was investigated for reaction in solid/solid, solid/semi-solid and solid/liquid states. The Fe2Al5 phase was formed as a major phase in the solid-state reaction and co-existed with the τ phase (Al5.5Cr1.95Fe2.55) as precipitates in a uniform layer in the semi-solid and liquid/solid reaction states. A porous two-phase layer consisting of Fe4Al13 and δ phase (Cr2Al13) was formed in the semi-solid and liquid/solid reaction states. The microhardness distribution of the formed intermetallic layer across the interface area was investigated along with the phase formation sequence in both thermodynamical and kinetically aspects.

Interfacial bonding mechanisms between aluminum and titanium during cold gas spraying followed by friction-stir modification

This paper closely evaluates the interfacial bonding mechanism between titanium particles deposited on an aluminum alloy substrate by cold gas spraying followed by friction-stir processing (FSP). After cold spraying and FSP modification, the produced Al/Ti interface was studied using focus ion beam-transmission electron microscopy (FIB-TEM) analysis and auger electron spectroscopy. Formation of a well-bonded titanium aluminide reaction layer was observed at the interface with a thickness in the range of 10–20 nm and a coherent interface associated with an inter-diffusion distance of about 600 nm. The results of this study showed that the physical bonding phenomenon during cold spraying according to the well-known adiabatic shear instability at the interface can be associated with chemical bonding and formation of an intermetallic layer at the interface during FSP modification. This is aided by the induced thermo-mechanical processing and deformation-assisted solid-state diffusion-based reactions. Also, these possible interfacial bonding and intermetallic layer formation mechanisms were discussed based on the inter-diffusion of elements at the Al/Ti interface based on the well-established Boltzmann-Matano theory and kinetics models correlated with experimental observations. The main findings of this research highlight the role of FSP on the performance of cold spray coatings as a post-processing technique to promote densification and homogenization during processing by promoting nano-scale interfacial mechanisms and chemical bonding at the interface.

Mechanism and Kinetics of Formation of Intermetallic Layers on the Surface of Steel Press Molds in Casting of Silumins

Regular features of the mechanism and kinetics of formation of transition layers under interaction between castable silumins and die steel 4KhVMFS (DI-22) used for making press molds are determined. The process of dissolution of the material of the press molds in AL-2 (AK12) silumin is accompanied by formation of aluminum-enriched intermetallic compounds of FeAl3 and Al4Si2Fe types and then by formation of Fe2Al5 and Fe3 Al intermetallic compounds with elevated iron content on the contact surface. Cross diffusion of aluminum is activated in regions under the continuous intermetallic layer on the surface of the mold and causes formation of a layer of a solid solution of aluminum in the steel, which is responsible for sticking of the material of the casting to the mold.

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.

Characterization of fully and partially penetrated Nd: YAG laser-weld dissimilar metal joints

Welding dissimilar metals and alloys is essential to emerging new technologies in manufacturing industries. This process is difficult because of the formation of intermetallic layers and the variations in the chemical and mechanical properties in the weld region. This paper aimed to characterize fully and partially penetrated dissimilar metal weld joints. The welding experiments were conducted on 0.5 mm-thick dissimilar weld joints for the investigation of the effects of the process parameters on the weld joints. Variations in chemical composition, oxide formation, imperfections and mechanical properties were analyzed. Results revealed that the weld joint characteristics notably deviated from the base metal properties in terms of hardness, strength, chemical composition, oxide formation and other constituents of the weld pool region. This study offers insight into the effects of process parameters and the necessary changes in weld composition for the improvement of welds joints.

Weld microstructure and mechanical properties in ultrasonic enhanced friction stir welding of Al alloy to Mg alloy

A preliminary investigation was carried out into the application of angularly exerted ultrasonic vibrations in friction stir welding for the joining of AA 6061-T4 alloy to AZ31B at different tool rotation speeds. The variations in the welding process and weld properties due to the applied acoustic field were investigated. The process temperature was increased, the material flow path was widened and mechanical interlocking features at weld interfaces were improved in the presence of ultrasonics. Morphology and distribution of intermetallic compounds were influenced by the added vibrations at all rotation speeds. Formation of intermetallic layers at the weld interfaces was driven by heat input. Composition of the intermetallic compound was roughly unaffected but the layer thickness was reduced by the additional acoustic field. The ultrasonic enhanced improvement in weld mechanical properties was significant at very low rotation speeds but less substantial at higher rotation speeds.

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.

Formation of catalytically active layers on the surface of polymetallic alloys

A new method for the synthesis of catalysts on polymetallic supports via the formation of intermetallic (aluminide) layer on the support surface followed by leaching and stabilization of the layer has been proposed. The intermetallic layer structure and distribution of elements in the layer were studied by scanning electron microscope considering a nickel chromium stainless-steel grid as an example. The morphology and elemental composition of the active phase on the catalyst surface were studied. The complex structure of this phase was found to consist of two types of entities with different composition located on the continuous highly porous substrate. The catalyst sample was tested in deep oxidation of CO and propane and demonstrated high activity. The developed method can be used to obtain new high-performance polymetallic catalysts.

Influence of the structure and phase composition of the bond interface on aluminium–copper lap welds strength

ABSTRACTThe structure and phase composition of the bond interface of aluminium–copper lap welds produced by friction stir welding and tool-assisted friction welding were analysed. Microstructural analysis proved that no through-interface material flow took place in tool-assisted friction welding and that aluminium–copper joining resulted from the formation of a thin and continuous intermetallic layer at the lap interface. For the welds produced by friction stir welding, evidences of through-interface material flow were found, promoting mechanical interlocking of both base materials, at the lap interface, and formation of discontinuous intermetallic layers. Mechanical testing showed that the tool-assisted friction welds, with excellent surface finishing, had low strength, contrary to the friction stir welds, which displayed excellent bond strength. The comparison of the mechanical and microstructural results, for both weld types, pointed to the ineffectiveness of the continuous intermetallic layer in providing high strength bonding.

Formation of a diffusion-based intermetallic interface layer in friction stir welded dissimilar Al-Cu lap joints

The joining of dissimilar metals is an important issue in modern lightweight design. Friction Stir Welding (FSW) is suitable for this task since the solidus temperature is usually not exceeded during the process. As a consequence, dissimilar joints can be produced with a minimum of deteriorating intermetallic phases. The latest studies showed the formation of intermetallic layers at the bonding interface with no significant negative influence on the seam quality. In this study, those intermetallic nanolayers at the interface of aluminium / copper lap joints were analysed. For the experiments, the commercially pure alloys EN AW-1050 and CW008A were chosen. The process temperature changed with respect to the parameter setup and was measured at different locations of the seam. The intermetallic layers at the interface were analysed by scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM). The experiments show that the thickness of the interlayer clearly correlates with the process temperature using an Arrhenius equation. It is supposed, that the rotating probe removes the oxide layers of the metal surfaces and a metallic bonding between the Al- and the Cu-phase is formed. Due to the elevated temperature after the probe has passed, the intermetallic layer has emerged by interdiffusion.

Molten aluminium attack on iron based alloys

Liquid aluminium alloys affect the moulds, by formation of intermetallic layers at their surface; such attack is enhanced by the flow of the molten metal on the surface of the tooling. Metal tooling are used to promote high heat transfer rates and increase the solidification rate to enhance mechanical properties in cast pieces, but the damage to their surface affects their quality and increases the production costs due to the need to repair them. This work presents the results of a series of studies conducted to evaluate the attack produced by molten aluminium on samples of iron based materials commonly used in the manufacture of dies and moulds. The studies were conducted in a machine that imposes a rotating movement to experimental specimens to simulate the flow of liquid metal. The damage observed in the samples was compared to that experienced by tooling in the melt shop.

Influence of Ag-modified graphene nanosheets addition into Sn–Ag–Cu solders on the formation and growth of intermetallic compound layers

In this study, varying amounts of Ag-modified graphene nanosheets (Ag-GNSs) were added to Sn–Ag–Cu (SAC) solders to synthesize composite solders. Then, the morphology and thickness of the intermetallic compound (IMC) layers were investigated during the liquid–solid reactions and isothermal aging. The test results revealed that the IMCs were scallop-shaped after soldering, but they changed from scallop-shaped to an irregular shape with increasing aging time. The IMC thickness and diffusion coefficients of the composite solders were both found to be lower than those of the plain solders. Moreover, it is worth noting that with the same amount of reinforcement, the composite solders reinforced with Ag-GNSs exhibited thinner IMC layers and lower diffusion coefficients than the solders reinforced with GNSs alone. Furthermore, Ag-GNSs prepared using ball milling yielded thinner IMC layers and lower diffusion coefficients than the same amount of Ag-GNSs prepared via mechanical mixing using a blender. Our results indicate that Ag-GNSs are more influential on delaying the growth of IMC layers than GNSs alone and that ball milling has advantages over mechanical mixing using a blender for the preparation of Ag-GNS composite solders.

Characterization of Cu–Ti powder metallurgical materials

Powder metallurgical Cu–Ti alloys with different titanium additions produced by hot pressing were characterized by optical microscopy, scanning electron microscopy, X-ray diffraction analysis, and hardness, wear and bending tests. The addition of titanium to copper caused the formation of different intermetallic layers around titanium particles. The titanium content of the intermetallics decreased from the center of the particle to the copper matrix. The hardness, wear resistance, and bending strength of the materials increased with increasing Ti content, whereas strain in the bending test decreased. Worn surface analyses showed that different wear mechanisms were active during the wear test of specimens with different chemical compositions. Changes in the properties of the materials with titanium addition were explained by the high hardness of different Cu–Ti intermetallic phases.

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.

Role of zinc layer in resistance spot welding of aluminium to steel

Effects of zinc layer on microstructure and mechanical behavior of resistance spot welds of aluminum to galvanized (GS-Al joint) and low carbon steel (PS-Al joint) were explored. The results showed that although nugget ‘volume’ in PS-Al joint was larger, the nugget ‘diameters’ of PS-Al and GS-Al joints were almost the same in size since the melted zinc layer was pushed toward the outer regions of the nugget. Melting and evaporation of zinc coat led to reduction of Al-Fe intermetallic layer thickness. Presence of zinc also reduced the fixture-induced tensile stress. Utilizing carbon steel fixtures during welding caused a sensible vibration in the joint members. The vibration resulted in fragmentation and decrease of the intermetallic compounds at the joint interface. Moreover, while PS-Al joints showed higher strength than that of GS-Al ones at the welding currents <12kA, fracture load of GS-Al welds exceeded PS-Al joints beyond 12kA. Low welding current resulted in an incomplete joint at GS-Al welds. However, lower induced tensile stress, as well as the formation of intermetallic layer with the thickness smaller than the critical value (~5.5μm) in GS-Al joints, led to superior mechanical properties at high welding currents.