Thickness Of Compound Layer Research Articles

Microstructural Characterization and Mechanical Properties of AA5083 Aluminum to AISI 1018 Steel Welds by Electro Spark Microwelding

ABSTRACT Welding of aluminium alloys to steels has been always challengeable. There are a certain number of methods to join these dissimilar metals all have their advantages and disadvantages. Advancement of any aluminium to steel welding strategies is an approach to control the size and nature of the intermetallic compound layer. A new method of electro spark microwelding has been developed for dissimilar welding of an aluminium alloy to steel to improve the joint mechanical properties. The microstructure of the welds are investigated by scanning transmission electron microscopy. The maximum tensile strength reached 206 MPa representing 65% of the tensile strength of the parent aluminium alloy with a ductile fracture locating at the fusion zone. The excellent bonding of the aluminium alloy and steel was based on the combined effects of the formation of about 4 μm thick nanoscale Fe rich intermetallic compound layer and complex mechanical inter-locking. The current research confirmed that aluminium could be successfully welded to steel via electro spark microwelding process.

Interface stability and fracture mechanism of Al/Steel friction stir lap joints by novel designed tool

A novel welding tool, characterized by the enlarged pin design was developed to solve the hook feature or insufficient interface deformation for Al/steel friction stir lap welded joints. The welding tool enhanced the interface deformation effect and eliminated hook feature. The thickness of the intermetallic compound (IMC) layer at the interface decreased from 3.3 μm to 0.46 μm, when the welding speed increased from 30 mm/min to 300 mm/min. The laminated structure composed of IMCs and fine steel grains gradually disappeared, with the interface gradually changing from serrated to straight as welding speed increased. The nanohardness value of the microstructure reached 9.4 ± 0.3 GPa at a distance of 10 μm from the interface layer. Due to the larger metallurgical bonding area, the best line load 499.4 N/mm reached 52 % of the 3 mm 6082-T6 alloy, which was obtained at the rotational speed of 1200 r/min and the welding speed of 50 mm/min. Four different interface failure modes were found and established during the shearing process. The strain concentration phenomenon of the successive occurrence, development and transfer of interface failure presented obvious interval characteristics in time and space.

Al-steel dissimilar joining: Challenges and opportunities

Al-steel joining has a lot of use in the automotive and aerospace industries since it saves a lot of weight. The materials' physical, thermal, and metallurgical qualities differed significantly, making connecting this combination difficult. This article provides a comprehensive overview of the Al-steel joining processes. The fundamental reason for the problem in fusion joining operations is the formation of a thick intermetallic compound (IMC) layer and additional difficulties related to solidification. The effects of heat input, wettability, and IMC layer on joint formation are summarised in this article. To achieve a good joint, numerous elements like heat generation, IMC formation, and process parameters must be critically balanced in solid-state joining processes. The effects of process parameters in friction stir welding (FSW) techniques on joint's mechanical and metallographic soundness are explored in this work. Because of the steel's higher strength, there have been various attempts to soften it and make it easier to deform in order to improve weld amalgamation. The use of tungsten inert gas (TIG) welding and electrical resistance heating to achieve heat-assisted hybrid friction stir welding has been documented in the literature. The hybrid joining processes are found to be improving the joint's tensile properties.

Effects of intermetallic compound layer thickness on the mechanical properties of silicon-copper interface

Intermetallic compounds (IMC) are found in the dual-layer composite, such as Si/Cu composite in multilayer semiconductor structures, and are often ignored in simulations that aim to predict the mechanical properties. The interface model of Si/Cu composites with different thickness of IMC layer is first established by molecular dynamics simulation. Then this study analyzed the elastoplastic behavior and adhesion behavior of the Si/Cu interface and the effect of IMC on the fracture properties. The simulation results demonstrate that the Si/Cu interface fails in a quasi-brittle fracture mode. The crack propagates along the interface between Si and the IMC layer. An apparent dislocation emission and large plastic deformation are found exclusively in the Cu layer. The thickness of the IMC layer increased from 2 to 10 Å, and the critical strain energy release rate increased from 14.48 J/m2 to 19.76 J/m2, while the equivalent modulus is not increase monotonically. Therefore, the IMC is of high significance for predicting the mechanical properties of the dual-layer composite.

A systematic study on the effect of coating type and surface preparation on the wettability of Si-Bronze brazing filler material on GI and GA-coated DP600

Zn-coated advanced high strength steels are popular in the automotive industry due to their excellent combination of mechanical strength and ductility as well as superior corrosion resistance provided by the Zn-coating – with hot-dip galvanized and galvannealed coatings being the most popular. Gas metal arc brazing technology is a non-fusion joining method, proposed as an alternative to the gas metal arc welding process due to several advantages: The arc-brazing process delivers significantly lower heat input to the substrate, which minimizes the Zn-coating burn-off leading to higher corrosion protection for the joined parts, and reduces the HAZ softening phenomenon which affects the mechanical integrity of the substrate, while at the same time reduces welding defects such as porosity and blowholes. The strength of an arc-brazed joint depends on the spreading of the molten filler material over the joint to create a bond between the parts as the molten braze solidifies. Existing literature on the subject suggests that heat input is the main driving factor controlling the wettability of the molten braze material with the type of shielding gas used also having an effect. However, the influence of different types of Zn-coatings and their respective surface condition (i.e., clean, or unclean) on the wettability of Cu-based molten braze materials during arc-brazing has not been investigated. The present work investigates the effect of surface morphology of galvanized and galvannealed DP600 steel in the as-received and plasma cleaned conditions on the wettability of molten Si-Bronze (CuSi3Mn1) brazing filler material in the bead-on-plate configuration. The findings of this work clearly demonstrate that the type of coating and its surface condition has a significant effect on the spreading of the molten filler material and on the growth of the intermetallic compound layer at the joint interface and therefore, should be taken into consideration as a factor that can impact the efficacy of an arc-brazed joint. • Evaluating surface morphology of different Zn-coatings to calculate their surface free energy. • Establishing a clear link between the surface roughness of Zn-coated steels on the wettability of molten Si-Bronze filler material. • The study shows that the wettability of the molten filler material is also affected by the presence of organic contaminants on the coating surface. • This work shows the relevance of surface morphology in controlling the wetting length of weld brazed joints. • The thickness of the intermetallic compound layer at the braze interface can be controlled by using oxygen plasma cleaning.

Effect of dwelling time and plunge depth on the joint properties of the dissimilar friction stir spot welded aluminum and steel

Sound joints of a far apart property, pure aluminum and mild steel, dissimilar materials were obtained by friction stir spot welding (FSSW) solid state joining process. Sheets of 2 mm thickness were overlapped and fixed with a fixture device then welded. Welding parameters that produced the sound joint were identified. Joints microstructure and mechanical properties were investigated. A microstructural investigation has revealed a creation of mechanical interlocking and discontinuous formation of the intermetallic compounds found at the interface. The intermetallic compound (IMC) layer thickness ranged from 6 μm to 17 μm with the optimum condition specimen, 800 rpm and 5 Sec dwell time. Tensile–shear test showed that failure load has increased with increasing tool plunge depth and rotational speed. After the optimum value of rotational speed, the shear failure load decreased. The maximum shear failure load of 2.15 KN attained at 800 rpm and 2.4 mm plunge depth.

Effect of aging time and loading rate on fracture behavior of Cu/Sn-0.7Cu solder joints

The effects of aging time and loading rate on the mode-I fracture behavior of the lead-free Cu/Sn-0.7Cu solder joint was studied using double cantilever beam (DCB) specimens. The variations in critical energy release rate for crack-initiation (Gci) of the joint, intermetallic compound (IMC) layer thickness, energy dispersive spectroscopy (EDS), and scanning electron microscopy based fractography were used to explain the fracture behavior. The fracture tests of DCB specimens aged at 200 °C for 6 to 96 h showed that increasing the aging time significantly decreased the Gci of the joint. This decrease in Gci with aging was attributed mainly to an increase in IMC layer thickness with aging time as well as change in failure behavior from ductile within the solder to brittle about the IMC layer. As the cross-head speed is increased from 0.1 to 500 mm/min, the Gci of the joint initially increased and then significantly decreased. The decrease in Gci with increasing loading rate is due to change in failure behavior from ductile within solder to brittle about solder-IMC interface.

Concurrent influences of tool offset and ultrasonic vibration on the joint quality and performance of dissimilar Al/Cu friction stir welds

Dissimilar joints made of aluminium alloy (Al) and copper (Cu) have great prospective applications in the electrical and electronic industries. Still, it is a challenging task to join them and obtain good performance. In this study, dissimilar AA6061-T6 and C10100 joints were produced by friction stir welding (FSW) and ultrasonic vibration-assisted friction stir welding (UVaFSW) processes with three different tool offset degrees from the Al side to the Cu side. Tool offset towards Al base material and in the Al/Cu interface produced defect-free joints with sound strengths in both joints made with and without ultrasonic vibration. On the other hand, tool offset towards Cu base material produced unsound joints with defective features such as wormholes and a lack of surface fill in both joints made with and without ultrasonic vibration. Ultrasonic vibration addition favoured a drastic reduction in the intermetallic compound (IMC) layer thickness, particularly amongst the welds made with tool offset in the Al/Cu interface, than those made with tool offset towards Al base material. In addition, the influence of tool offsets and the ultrasonic vibration addition remarkably affects the sizes (particle areas and the minimum Feret diameters) and the concentration of the Cu particles distributed in the weld nugget. In the joints produced with tool offset towards Al base material, the particle areas and the minimum Feret diameters were decreased by ~73.3% and ~42.6%, respectively, with the ultrasonic vibration addition. On the other hand, ultrasonic vibration in the joints produced with tool offset in the Al/Cu interface resulted in decreased particle areas and the minimum Feret diameters by ~60.6% and ~24.6%, respectively. The joints made with ultrasonic vibration have higher tensile strength than those made by conventional FSW.

Performance enhancement by novel plasma boron-nitriding for 42CrMo4 steel

In order to further enhance the performance of the components previously treated by plasma nitriding (PN) and meet the technical requirements proposed by the cooperative enterprise, plasma boron-nitriding (PNB) was primarily developed for 42CrMo4 steel at 520 °C for 6 h by adding a little Ferroboron around the samples during the process of plasma nitriding. The results show that plasma boron-nitriding (PNB) can significantly increase the surface hardness of the sample from 750HV0.05 to 1002HV0.05 due to the formation of very hard borides of FeB and Fe2B, and the thickness of compound layer is increased from 18.78um to 29.44um, the effective diffusion layer is increased from 265um to 355um, which is equivalent to an increase of nitriding efficiency by about 35%. At the same time, the wear resistance of the samples treated by PNB is significantly enhanced, the wear marks turns to be much shallower and narrower, and the wear rate is decreased from 3.06 mg/cm2 to 1.02 mg/cm2.

Shear Strength Degradation Modeling of Lead-Free Solder Joints at Different Isothermal Aging Conditions

Abstract SAC-based alloys are one of the most common solder materials that are utilized to provide mechanical support and electrical connection between electronic components and the printed circuit board. Enhancing the mechanical properties of solder joints can improve the life of the components. One of the mechanical properties that define the solder joint structure integrity is the shear strength. The main objective of this study is to assess the shear strength behavior of SAC305 solder joints under different aging conditions. Instron 5948 Micromechanical Tester with a customized fixture is used to perform accelerated shear tests on individual solder joints. The shear strength of SAC305 solder joints with organic solderability preservative (OSP) surface finish is investigated at constant strain rate under different aging times (2, 10, 100, and 1,000 h) and different aging temperatures (50, 100, and 150°C). The nonaged solder joints are examined as well for comparison purposes. Analysis of variance (ANOVA) is accomplished to identify the contribution of each parameter on the shear strength. A general empirical model is developed to estimate the shear strength as a function of aging conditions using the Arrhenius term. Microstructure analysis is performed at different aging conditions using scanning electron microscope (SEM). The results revealed a significant reduction in the shear strength when the aging level is increased. An increase in the precipitates coarsening and intermetallic compound (IMC) layer thickness are observed with increased aging time and temperature.

Study of the mechanical properties and microstructures of conical joints for aluminum/steel continuous drive friction welding

Presetting the taper on a joint will change the thermodynamic cycle of the interface in the direction of the rotating friction radius and affect the structure and joint mechanical properties. In this research, five types of conical Q235 low carbon steel rods at 5°, 10°, 15°, 20°, and 25° were paired with 1060 aluminum rods performed with continuous drive friction welding butt joint experiments. For these experiments, the temperatures of the interface center as well as 1/3R and 2/3R were collected during the welding process. After welding, the joints were subjected to tensile testing, fracture analysis, and microstructure analysis of the joint interface. The results showed that for the same process parameters, the increase in the tilt angle of the conical end face made the corona bonds of the friction interface of the joint move from the outside to the inside due to a decrease in the friction heat and an increase in the tangential stress, and the corona bonds became narrower. For certain technological conditions, a reasonable cone could improve the homogenization of the radial intermetallic compounds at the joint interface. The thickness of the intermetallic compound layer of the 15° tilt angle joints had the smallest gradient along the radius. The average thickness was about 0.85 μm and the average tensile strength reached a maximum of 77.5 MPa. This was 96 % of the base material of 1060 pure aluminum.

Interfacial Bonding and Mechanical Properties of Al/Mg Dissimilar Refill Friction Stir Spot Welds Using a Grooved Tool

Al/Mg dissimilar welds were successfully fabricated by refill friction stir spot welding using a grooved sleeve tool. Influences of sleeve penetration depth and rotational speed on the weld formation and mechanical performance were systematically evaluated in terms of welding parameter optimization, interfacial bonding mechanism, hardness distribution and welded joint strength. The results indicated that the success of joining Al alloy to Mg alloy significantly depends on tool sleeve penetration depth. The interfacial bonding mechanism compromised both metallurgical bonding and mechanical inter-locking. Intermetallic compound layers of Al3Mg2 and Al12Mg17 were formed at the Al/Mg interface. The thickness of the intermetallic compound (IMC) layer at the weld center increased from 20–30 μm to 40 μm when the rotational speed increased from 1000 to 2000 rpm. The minimum hardness was 80 HV in Al 7075 and 52 HV in ZEK 100; both were measured in the heat affected zone. The welded joint lap shear strength decreased, and the scatter increased with the increasing of rotation speed, whose maximum was 3.6 kN when the rotational speed was 1000 rpm. In addition, the failure mechanism was determined by tool rotational speed, and found to be interfacial failure under a rotational speed of 1000 rpm and nugget pullout under a rotational speed of 2000 rpm.

Nanocomposite SAC solders: the effect of heat treatment on the morphology of Sn–3.0Ag–0.5Cu/Cu solder joints reinforced with Ni and Ni–Sn nanoparticles

The concept of nanocomposite lead-free solders has provided a promising approach to improve mechanical reliability of solder joints. Minor additions of metal nanoparticles into the commonly used Sn–3.0Ag–0.5Cu solder impact on the morphology of both the solder alloy and solder/Cu joint. For instance, it was stated that the average thickness of the interfacial intermetallic compound layer between Sn–3.0Ag–0.5Cu solder and Cu substrate decreases by addition up to 2.0wt.% of nano-sized Ni and Ni–Sn particles. The present research is the follow-up of our previous study and is focused on the investigations of the thermal aged Sn–3.0Ag–0.5Cu solder joints with up to 2.0wt.% of nano-sized Ni, Ni3Sn and Ni3Sn2 inclusions. The produced Cu/nanocomposite solder/Cu joints were kept at the temperature of 423 K for 10 and 20 days. Based on the average thickness of the interfacial intermetallic compound layer Cu6Sn5/Cu3Sn estimated for solder joints with different aging time, the growth kinetics of the interfacial IMC layer was examined.

Effect of Er content on the interfacial microstructure, shear properties and creep properties of Sn58Bi joints

The influences of Er content on the interfacial microstructure shear properties and creep properties of Sn58Bi joints were investigated in this study. The intermetallic compound composition of Sn58Bi-xEr/Cu was Cu6Sn5 compound. The addition of Er suppressed the activity of Sn element, decreased the driving force for the growth of Cu6Sn5 intermetallic compound and decreased the thickness of Cu6Sn5 intermetallic compound layer. The shear properties and creep durability of Sn58Bi-xEr/Cu welded joints were improved to a certain extent. At the Er content of 0.1%, the shear strength and creep durability properties of the solder alloy are relatively optimal. When wt%Er was more than 0.1%, with the increasing Er content of rare earth elements, the internal organization of the joint interface is coarsened, and the flatness of the IMC layer at the interface is reduced, which leads to the decrease of the creep performance of the final joint.

Interface strengthening of a roll-bonded two-ply Al/Cu sheet by short annealing

We investigated the influence of annealing on the microstructural evolution and mechanical properties of a roll-bonded two-ply clad sheet made of aluminum and copper alloys. Various microstructures were obtained via heat treatment at 400 °C. Initially Al2Cu and Al4Cu9 phases were indexed at interface whose overall thickness was 1 μm by annealing for 20 min. By the progress of annealing for 120 min, another thin intermetallic compound (IMC) layer, AlCu phase, was formed between initially generated Al2Cu and Al4Cu9 layers. Total thickness of IMCs was considerably increased by 3.12 ± 0.24 μm. Uniaxial tensile and peel tests were performed and the results indicated simultaneous improvements of the bonding strength and elongation without much expense of tensile strength by suitable short-time annealing for 10 min at 400 °C, where the aluminum‑copper joint kept its mechanical integrity when the overall thickness of intermetallic compound layers limited less than 1 μm.

Study on the microstructure and mechanical property of Cu-foam modified Sn3.0Ag0.5Cu solder joints by ultrasonic-assisted soldering

Cu-foam sheets with the thicknesses of 0.15 mm and 0.5 mm were utilized as strengthening structure to improve the performances of the Sn3.0Ag0.5Cu (SAC305)/Cu solder joints. The ultrasonic-assisted soldering was applied to manufacture the solder joints. The effects of Cu-foam and ultrasound-assisted soldering time on microstructure and mechanical property of solder joints were researched. Experimental results showed that excellent metallurgical bonding was generated between the copper substrate and the Cu-foam/SAC305 composite solder layer. The average thickness of interfacial intermetallic compound (IMC) layer decreased with the increase of ultrasonically soldering time, and a thinner interfacial IMC layer was found in the joints with ultrasonic treatment in narrow channels. With the ultrasonic soldering time prolonged, the Cu 6 Sn 5 grains became more refined. Some round-shape Cu 6 Sn 5 grains were transformed into hexagonal prismatic with the increase of the ultrasonic soldering time. The shear test was conducted for the solder joints under different soldering conditions. It was found that the shear strength of the Cu-foam/SAC305 composite solder joints were higher than that of SAC305 solder joints. The grain refinement caused by ultrasonic cavitation significantly improved the shear strength of the solder joints. Besides, the fracture behavior of solder joints without ultrasonic vibration was classified to be ductile-brittle mixed type while that with ultrasonic vibration was changed to be ductile type.

Performance of Sn-3.0Ag-0.5Cu Composite Solder with Kaolin Geopolymer Ceramic Reinforcement on Microstructure and Mechanical Properties under Isothermal Ageing.

This paper elucidates the effect of isothermal ageing at temperature of 85 °C, 125 °C and 150 °C for 100, 500 and 1000 h on Sn-3.0Ag-0.5Cu (SAC305) lead-free solder with the addition of 1 wt% kaolin geopolymer ceramic (KGC) reinforcement particles. SAC305-KGC composite solders were fabricated through powder metallurgy using a hybrid microwave sintering method and reflowed on copper substrate printed circuit board with an organic solderability preservative surface finish. The results revealed that, the addition of KGC was beneficial in improving the total thickness of interfacial intermetallic compound (IMC) layer. At higher isothermal ageing of 150 °C and 1000 h, the IMC layer in SAC305-KGC composite solder was towards a planar-type morphology. Moreover, the growth of total interfacial IMC layer and Cu3Sn layer during isothermal ageing was found to be controlled by bulk diffusion and grain-boundary process, respectively. The activation energy possessed by SAC305-KGC composite solder for total interfacial IMC layer and Cu3Sn IMC was 74 kJ/mol and 104 kJ/mol, respectively. Based on a lap shear test, the shear strength of SAC305-KGC composite solder exhibited higher shear strength than non-reinforced SAC305 solder. Meanwhile, the solder joints failure mode after shear testing was a combination of brittle and ductile modes at higher ageing temperature and time for SAC305-KGC composite solder.

Modified friction stir clinching-brazing of brass to AA5083 aluminum alloy using Zn interlayer

The modified friction stir clinching (MFSC) of 5083 aluminum alloy to brass using pure Zn interlayer has been explored and elucidated for the first time. By that, the influence of the Zn interlayer thickness on the microstructure and the mechanical properties of the 5083/brass joint was investigated. The attained data have revealed that the intermetallic compound (IMC) layer thickness was mainly influenced by the Zn interlayer. The use of the Zn interlayer restrained the creation of brittle Al–Cu IMCs such as Al4Cu9 during the MFSC process and, in return, softer phases such as Cu4Zn, CuZn5, and CuZn were formed. It was also found that with increasing the thickness of the Zn interlayer from 50 to 100 µm, the thickness of the brazed zone increased and the tensile/shear strength of the spot welds significantly improved from 5250 to 8490 N (approximately 60% increment over the welded sample with 50-µm-thick Zn) which can be ascribed to supreme bonding and homogeneous brazing zone at the interface.

Influence of Plasma Nitriding with a Nitrogen Rich Gas Composition on the Reciprocating Sliding Wear of a DIN 18MnCrSiMo6-4 Steel

In this study, the sliding wear of a DIN 18MnCrSiMo6-4 continuous cooling bainitic steel plasma nitrided with a nitrogen rich gas composition was investigated. To evaluate the influence of processing time and temperature on mechanical and microstructural characteristics of nitrided layer, the samples were nitrided at 400, 450, 500 and 550 °C for 3, 6 and 9 h. The produced nitrided layers were characterized concerning the microstructure, phase composition, microhardness and surface roughness. The samples were tested by ball-on-flat reciprocating dry sliding for friction coefficient and wear analysis. The tests were stopped after a given damage criteria involving the rapid growth of the friction coefficients and wear. The correlation of the different treatment parameters and resulting case depths and surface hardness with sliding distance at the time of microcracks formation or delamination of the surface layer was evaluated statistically by the analysis of variance (ANOVA). The plasma nitrided samples at 550 °C showed better wear performances in the ball-on-flat tests than the other groups investigated, since these samples have a thicker compound layer and diffusion zone higher than the other conditions investigated. In general, the beginning wear is slower because of the hardest region of the compound layer.

Evaluation of mechanical properties of cold roll bonded mild steel and aluminum

Abstract The need for joints between dissimilar materials often is used in automobile industries, electrical components and so on. This need of dissimilar metal joining is fulfilled by various solid state welding processes. Cold roll bonding (CRB), as a solid phase method of bonding same or different metals by rolling at room temperature, has been widely used in manufacturing large layered composite sheets and foils. It has various advantages such as good surface quality, low cost, fast process, easy to automate and no additional equipments except rolling mills are required. In this research work, CRB of Mild Steel (MS) and wrought Aluminum (w-Al) strips was studied. Bonded sheets of w-Al and MS are used for cylinder liners and bearings. CRB of w-Al and MS sheets was carried out on two high rolling mill. These bonded sheets were then diffusion bonded with permutations of temperature and time to find out the probable phases at the interface and the intermetallic compound layer thickness. Effect of the processing parameters on bonding strength, microstructure, hardness and grain-size and the formed intermetallic phases were also studied. The tensile shear strength of the CRB strip increased to a maximum of 48.95 MPa with increase in reduction to 27%. As temperature and time of diffusion bonding increases, the thickness of intermetallic compound layer increases. During heat treatments, there was considerable Al diffusion into the MS or in other words Fe side near the interface where Al-rich intermetallics formed. XRD analysis confirmed this with the presence of high intensity peaks of aluminium rich intermetallic compounds e.g Fe2Al5, FeAl3 and FeAl2 at the interface. The activation energy for diffusion of Al to Fe was found to be 160 KJ/mol.