Thickness Of Intermetallic Layer Research Articles

Microstructural and mechanical characterization of Al/Cu interface in a bimetallic composite produced by compound casting

The bimetal set (Al/Cu) with Cu wire with 2.0, 2.5, and 3.0 mm diameters were cast at different casting temperatures and solidification times through the compound casting method. The microstructure of solid/liquid diffusion bonding at the Al/Cu interface was investigated, and the shear strength of the Al/Cu interface was measured by punch test. By characterizing the diffusion layer, the optimum parameters of the compound casting, including the casting temperature and the solidification soaking time, as well as the Cu wire diameter, were acquired. The intermetallic compounds (IMCs) such as CuAl2 were observed in the diffusion layer. The types of intermetallic phases and diffusion layer thickness affect the hardness and the shear strength. The result of casting at 680 °C and solidification soaking time of 15 s for 3 mm Cu wire, shows that IMCs increased the micro-hardness of the Al/Cu bimetal up to 328 HV at the Al/Cu interface. Also, increasing the solidification soaking time at a constant temperature resulted in a growth of the interface layer’s thickness, which exhibits a lamellar eutectic microstructure containing IMCs. Furthermore, this action caused an increase in the shear strength.

Al-Cu intermetallic phase growth in hybrid metal extrusion & bonding welds exposed to isothermal annealing or direct current cycling

Joining of aluminium (Al) to copper (Cu) is of great interest to power generation, transportation and electronic industry. However, dissimilar metal joining often promotes intermetallic phase formation at the joined interface, which in redundancy can cause mechanical degradation and increased electrical resistance. The welding technique hybrid metal extrusion & bonding (HYB) is proven capable of joining dissimilar metals with a total intermetallic phase layer thickness <▪. To test how Al-Cu HYB joints perform as electrical conductors, a 6101 Al alloy HYB-welded to Cu is exposed to heat treatment at ▪ or cycling of direct current density up to ▪. In-depth micro- and nanostructure characterisation by (scanning) transmission electron microscopy and atom probe tomography are used to describe the structure and chemistry of the formed intermetallic phases.The Al-Cu HYB joints exhibited resilience against intermetallic phase growth during isothermal heat treatment or exposure to electric current. However, a non-symmetry is observed dependent on the current direction, creating voids in Cu near, and in the intermetallic layers when the current goes from Al to Cu. Detailed microstructure characterisation unveils Si and Mg in the intermetallic phase layers. Their origin and role in intermetallic phase growth are discussed.

The Feasibility of Static Shoulder Friction Stir Welding in Joining Dissimilar Metals of Al6061 and Ti6Al4V

In this study, static shoulder friction stir welding (SSFSW) is innovatively employed to join Al6061 and Ti6Al4V, aiming to minimize material mixing and intermetallic formation, significantly influencing the interfacial microstructure and joint strength. The results revealed that SSFSW reduced the intermetallic layer thickness at the interface, improving joint quality. The mutual interdiffusion of Al and Ti at the interface was influenced by an exothermic chemical reaction, forming an Al5Ti2–Al3Ti sequence due to the diffusion of Al into the Ti matrix. The microstructural analysis demonstrated better interfacial microstructural homogeneity in SSFSW joints than conventional FSW (CFSW), with finer titanium particle distribution. The larger particles resulted in coarser grains in CFSW, affecting the mobility of dislocations, which potentially led to the inhomogeneous concentration of dislocations at the interface. Recrystallization mechanisms varied between CFSW and SSFSW, with the Ti interface showing equiaxed and recrystallized grains due to the dynamic recovery driven by adiabatic shear bands. The tensile testing results of SSFSW exhibited a joint efficiency of 88%, demonstrating a 20.2% increase compared to CFSW, which can be attributed to differences in fracture modes. This study contributes to an understanding of dissimilar Al-Ti joining and provides insights for industries seeking to leverage the benefits of such combinations in lightweight and high-performance structures.

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.

Enhancing Microstructural, Textural, and Mechanical Properties of Al-Ti Dissimilar Joints via Static Shoulder Friction Stir Welding

Abstract The present study explores the application of static shoulder friction stir welding (SSFSW) to address the challenges of poor mechanical properties in conventional Al-Ti dissimilar friction stir joints, which arise due to significant material mixing and the formation of thick intermetallic layers. The results show that SSFSW inhibited material mixing and the mutual diffusion of Al and Ti were suppressed due to lower heat input. Mutual interdiffusion of Al and Ti was directed by an exothermic chemical reaction, forming an Al5Ti2 – Al3Ti sequence due to sluggish diffusion of Al in Ti at a temperature of 512°C achieved in this study. The microstructure at stir zone (SZ) comprised equiaxed grains with Ti particles acting as dispersoids for nucleation, whereas the presence of large Ti blocks at SZ of Conventional FSW (CFSW) resisted plastic deformation, resulting in non-homogeneous concentration of dislocations near its interface. A significant decrease in grain size at all the critical zones of weldment was due to rearrangement of dislocations through slip-and-climb mechanism, as evidenced by the occurrence of dynamic recrystallization. Emergence of γ-fiber and basal fiber texture increased the tensile strength of SSFSW to 289 MPa, which is about 11.2% higher than CFSW, with joint efficiency of about 88%. The study also analysed the contribution of various strengthening mechanisms to the yield strength improvement of SSFSW weldments in detail of SSFSW weldments in detail, and the results showed that grain boundary strengthening contributed the most to strength improvement in SSFSW.

Minimizing material flow in the dissimilar joining of Al6061 and Ti6Al4V to mitigate the adverse effects of intermetallic compounds

Static shoulder friction stir welding (SSFSW) offers a promising solution for joining Al6061 and Ti6Al4V by addressing material mixing and intermetallic formation encountered in conventional friction stir welding (CFSW). SSFSW effectively suppresses material mixing and Al-Ti interdiffusion, leading to an Al5Ti2 – Al3Ti sequence through an exothermic reaction. Comparative analysis with underwater friction stir welding (UWFSW) highlights SSFSW's effectiveness, showing a significant reduction in intermetallic layer thickness compared to UWFSW. The intermetallic layer thickness of SSFSW is measured at 2.169 µm, while UWFSW exhibits a thickness of 3.731 µm, and CFSW shows the highest at 5.485 µm. The inverse pole figure confirms reduced material flow and intermetallic formation in SSFSW compared to UWFSW and CFSW.

Mechanical behavior of AA5083/AA6061 friction stir welds using modal analysis

Abstract Solid-state joining is used for welding similar or dissimilar materials due to its many advantages like avoiding fusion and formation of a thick intermetallic layer, etc. Determination of the right process parameters (feed rate and rotation speed) and tool geometry (shoulder and pin) is of critical importance in friction stir welding in order to achieve adequate weld quality. The experiments were performed using three process parameters: feed rate (mm min−1), rotation speed (rpm) and pin geometry for friction stir welding of Al5083 and Al6061. Eighteen experiments were performed with different process parameters and mechanical tests (microhardness and tensile measurements) have been carried out to determine the weld quality. Results showed that the best results of ultimate strength (198.5 MPa) were achieved by the triangle pin geometry, 1250 rpm rotation speed and 100 mm min−1 feed rate. Similar results were observed in microhardness tests. Effects of tool geometry, feed rate, and rotation speed on the vibration properties and weld quality are also investigated experimentally. The effects of the FSW parameters used were assessed using vibration analysis.

Effect of Al2O3 and NiO Nanoparticle Additions on the Structure and Corrosion Behavior of Sn—4% Zn Alloy Coating Carbon Steel

The application of a higher corrosion resistance coating modified with nano additions can effectively decrease or prevent corrosion from occurring. In the present work, a novel method is successfully developed for the modification of carbon steel surfaces aiming for high corrosion resistance using Sn—4% Zn alloy/nanoparticle composite (NiO+ Al2O3) coating. Sn—4% Zn alloy/nanoparticle composite (NiO+ Al2O3) coatings were deposed on carbon steel using a direct tinning process that involved a power mixture of Sn—4% Zn alloy along with a flux mixture. Regular coating and interface structures were achieved by individual Al2O3 and both NiO and Al2O3 nanoparticle combined additions in the Sn-Zn coating. The maximum coating thickness of 70 ± 1.8 µm was achieved for Al2O3 nanoparticles in the Sn-Zn coating. Interfacial intermetallic layer thickness decreased with all used nanoparticle additions in individual and hybrid conditions. The minimum intermetallic layer thickness of about 2.29 ± 0.28 µm was achieved for Al2O3 nanoparticles in the Sn—Zn coating. Polarization and impedance measurements were used to investigate the influence of the incorporated Al2O3, NiO, and hybrid Al2O3/NiO nanoparticles on the passivation of the low-carbon steel (LCS) corrosion and the coated Sn—Zn LCS in sodium chloride solution. It was found that the presence of Al2O3, NiO, and Al2O3/NiO nanoparticles remarkably improved the corrosion resistance. The corrosion measurements confirmed that the corrosion resistance of the coated Sn-Zn carbon steel was increased in the presence of these nanoparticles in the following order: Al2O3/NiO &gt; NiO &gt; Al2O3.

DC pulsed plasma magnetron sputtering of CdO/Cu/CdO multilayers thin films for self-cleaning and optoelectronic applications

In this study, CdO/Cu/CdO multilayers thin films were organized on glass substrates with different Cu intermetallic layer thickness engaging DC plasma magnetron sputtering. The optoelectronic properties and structural characteristics of the multilayers at various Cu intermetallic layer thicknesses which were varied from 4 to 16 nm were explored. The calculated band gap was reduced from 2.66 eV to 2.48 eV as the Cu intermetallic layer thickness increased from 4 to 16 nm. The refractive index and coefficient of extinction of CdO/Cu/CdO multilayers increased with increasing the Cu intermetallic layer thickness. The resistivity is reduced from 1.8 × 10−2 Ω cm for CdO single layer to reach a value of 2.7 × 10−4 Ω cm for CdO/Cu (16 nm)/CdO multilayer. Further, the sheet resistance is decreased from 1000 to 13.8 Ω/sq. with the variation in Cu intermetallic layer thickness from 0 to 16 nm. CdO/Cu (4 nm)/CdO multilayer film recorded the best figure of merit (2.3 × 10−4 Ω−1). After sunlight illumination for the multilayers, the surface wettability was improved and the contact angle recorded lowest value of nearly 24° for CdO/Cu (8 nm)/CdO and CdO/Cu (12 nm)/CdO.

Experimental study on drawability of aluminium-copper composite in micro deep drawing

To meet the increasing demand of multifunctional applications of microcomponents, metal composites have been gradually noted in micromanufacturing. In this paper, the formability of aluminium (Al)-copper (Cu) composite foils in micro deep drawing (MDD) was studied, and the mechanism involved was discussed. A two-layered Al-Cu composite with the thickness of 235 µm was selected and first rolled to 50 µm, and then annealed at 200, 300, 400 and 500 °C for 5 min prior to the MDD experiments. The results show that Al-Cu composite foil possesses the best combination of strength and ductility after annealing at 400 °C. With the increase in annealing temperature, the grains of both Al and Cu layers are refined, and in the meantime, the thickness of intermetallic layer also increases. The results from MDD tests indicate that the existence of intermetallic layer has a greater influence on the formability of the composite foil compared to the finer distribution of grains. On the basis of the obtained results, the optimised heat treatment method with the annealing temperature of 300 °C for 1 h was proposed, which was then proved to significantly improve the performance of the Al-Cu composite foil in MDD.

Friction stud riveting (FSR) of thick high-strength aluminum alloy structure

7-series aluminum (Al) alloy is a promising material that can meet the ever-increasing lightweight demand for transportation tools. However, the assembly between Al alloy and steel components brings challenges to the existing stud pre-embedded technology. This study proposes a friction stud riveting (FSR) process to achieve high-performance and high-efficiency embedding of steel studs in Al alloy parts by shank undercut, grooves interlock, and intermetallic compounds bonding. The stud geometry and FSR process were first optimized by evaluating the macro morphology of the joints. Then, the microscopic characterizations were performed to understand the material flow behavior, plastic deformation, and microstructure evolution of the joint induced by the feeding and rotation of the stud. The results indicate that the transient thermo-mechanical coupled FSR process leads to a continuous transition of sliding, mixed sliding-sticking, and sticking contact conditions between the stud and the Al alloy, resulting in a thermo-mechanical affected zone (TMAZ) outside the stud and a trapped Al alloy (TAA) inside the stud with diverse dynamic recrystallization (DRX) states and microstructures. The rotation state evolution and temperature gradients of the material within the TAA create two DRX bands that dominate the fracture behavior of TAA under tensile and shear loads. The strengths of the optimized steel stud-thick Al FSR joints reach 101.3% and 118.5% of the 7A52 Al alloy base material in tensile and shear tests, respectively, which solves the problem of low joining strength between steel stud and Al alloy plate due to the brittle and thick intermetallic compounds layers in conventional stud welding processes.

Fracture Behavior and Reliability of Low-Silver Lead-Free Solder Joints

Abstract Low-silver solders are increasingly being used because silver improves the tensile strength. In this study, the variation in fracture behavior with silver content in lead-free solder joints was studied using double cantilever beam specimens. Fracture tests were done with solder joints made with Sn-0.7Cu, SACX0307, and SAC305 solder materials. The critical energy release rate for crack-initiation (Gci) of the joint was correlated with the plastic zone just ahead of the precrack tip, intermetallic compound layer thickness, energy dispersive spectroscopy analysis, and scanning electron microscopy based fractography study. The Gci for Sn-0.7Cu solder joint was observed to be significantly higher than the other two solder joints. The fractography study revealed that the failure was ductile for Sn-0.7Cu and a mix of ductile and brittle for the other two solder joints. The extent of the plastic zone ahead of the crack tip, obtained from finite element modeling, was found to be significantly larger and the intermetallic compound layer was relatively thinner for Sn-0.7Cu solder joint compared to the other two solder joints. The ductile failure, significantly larger plastic zone size and thinner intermetallic compound layer resulted in significantly higher Gci for Sn-0.7Cu solder joint.

Corrosion resistance and metallurgical behaviour of CMT welded Al-LCS dissimilar butt joint exposed in simulated industrial environment

Cold Metal Transfer welding is a predominant process for joining the Aluminium and Low Carbon Steel (LCS) dissimilar joints with enhanced properties. In addition, these joints have vast application in various simulated industrial environmental conditions. However, the formation of thick intermetallic layers during welding over these joints leads to invoking the corrosion attack and causing a catastrophic failure that is the primary concern in life prediction of the joint. Hence, the corrosion behaviour of AL-LCS dissimilar butt joint exposed in the simulated industrial environment has been studied experimentally and it has been compared with the Cold Metal Transfer (CMT) welded aluminium and LCS similar joints. The potentiodynamic polarization and the electrochemical impedance spectroscopy were carried out in 3.5% aggressive sodium chloride medium with varying benzotriazole corrosion inhibitor with varying the concentrations like 10 ppm, 15 ppm and 20 ppm. The results showed that the corrosion resistance behaviour of CMT welded dissimilar joints are increased with increasing inhibitor concentration. The inhibitor showed effective performance, and the efficiency is also found to be 78–80% at 20ppm, which revealed the enhanced corrosion resistance of dissimilar metal joints in simulated industrial conditions. Finally, the dissimilar joints are characterized by sophisticated analytical techniques.

Enhancement of Surface and Interface Properties of Low Carbon Steel by Hybrid ZnO and NiO Nanoparticles Reinforced Tin Coating

Tin matrix nanocomposite coatings containing ZnO and NiO nanoparticles, both individually and combined, were deposited on low carbon steel substrates. The aim was to investigate the effect of reinforcement of nanoparticles on microstructural morphology and thickness of tin coatings, modification in the interfacial layer between coating and substrate, and the corrosion resistance of low carbon steel substrate. Optical and scanning electron microscopy were employed for microstructural observation, while potentiostat-galvanostat was utilized for electrochemical investigation. It was found that the tin nanocomposite coatings with nanoparticles significantly modified the coating thickness, intermetallic layer thickness, and surface corrosion resistance. Coatings through the direct tinning process are considered to be a simple and low-cost route for protecting metallic materials from corrosion, and the presence of ZnO and NiO nanoparticles in tin coatings further increases the corrosion resistance of low carbon steels.

Tunable metal contacts at layered black-arsenic/metal interface forming during metal deposition for device fabrication

Understanding the kinetics of interfacial reaction in the deposition of metal contacts on 2D materials is important for determining the level of contact tenability and the nature of the contact itself. Here, we find that some metals, when deposited onto layered black-arsenic films using e-beam evaporation, form a-few-nm thick distinct intermetallic layer and significantly change the nature of the metal contact. In the case of nickel, the intermetallic layer is Ni11As8, whereas in the cases of chromium and titanium they are CrAs and a-Ti3As, respectively, with their unique structural and electronic properties. We also find that temperature, which affects interatomic diffusion and interfacial reaction kinetics, can be used to control the thickness and crystallinity of the interfacial layer. In the field effect transistors with black-arsenic channel, due to the specifics of its formation, this interfacial layer introduces a second and more efficient edge-type charge transfer pathway from the metal into the black-arsenic. Such tunable interfacial metal contacts could provide new pathways for engineering highly efficient devices and device architectures.

Influence of Heat Input on Cold Metal Transfer Welded Joints

ABSTRACT During welding, the heat input is a critical parameter in determining the quality of the joints welded by any welding process. In the case of dissimilar welding, as dissimilar metals have significant differences in melting point, it is challenging to achieve an adequate joint. The emerging cold metal transfer welding process can resolve it effectively by controlling the heat while joining dissimilar metals. Therefore, in this research work, Aluminum-galvanized steel dissimilar joints were fabricated using varying heat inputs and their mechanical, metallurgical, and corrosion properties were evaluated. Furthermore, the second-phase formation at the weld interface has been investigated, and corrosion behavior is analyzed using electrochemical techniques in a 0.1% sodium chloride environment. The Tafel polarization and electrochemical impedance spectroscopy studies reveal it improved corrosion resistance due to an increase in heat input. The reduced solidification defects and the establishment of an appropriate intermetallic layer thickness with a suitable microstructure at the interface are the reasons for the improved corrosion resistance and strength of the dissimilar joints.

Understanding the Effect of Reflow Profile on the Metallurgical Properties of Tin–Bismuth Solders

Sn–Bi alloys are desirable candidates for soldering components on printed circuit boards (PCBs) because of their low melting point and reduced cost. While certain tin–bismuth solders are well characterized many new alloys in this family have been developed which need proper characterization. The following study looks at the behavior of four different Sn–Bi alloys—traditional 42Sn58Bi and 42Sn57Bi1Ag and two new tin–bismuth alloys—in solder paste during the reflow soldering process. Each alloy was processed using different reflow profiles that had varying times above liquidus (TALs) and peak temperatures. The PCBs were then analyzed to see how the processing variables influenced wetting, voiding, microstructure, intermetallic layer composition, and thickness. After analysis, the PCBs were then subjected to thermal cycling experiments to see how reflow profile impacted microstructure evolution. The results demonstrated that reflow profile affects properties such as metal wetting and voiding. It does not however, greatly impact key metallurgical properties such as intermetallic layer thickness.

Influence of Flux and Related Factors on Intermetallic Layer Growth within SAC305 Solder Joints.

Flux contained in solder paste significantly affects the process of solder joint creation during reflow soldering, including the creation of an intermetallic layer (IML). This work investigates the dependence of intermetallic layer thickness on ROL0/ROL1 flux classification, glossy or matt solder mask, and OSP/HASL/ENIG soldering pad surface finish. Two original SAC305 solder pastes differing only in the used flux were chosen for the experiment. The influence of multiple reflows was also observed. The intermetallic layer thicknesses were obtained by the image analysis of micro-section images. The flux type proved to have a significant impact on the intermetallic layer thickness. The solder paste with ROL1 caused an increase in IML thickness by up to 40% in comparison to an identical paste with ROL0 flux. Furthermore, doubling the roughness of the solder mask has increased the resulting IML thickness by 37% at HASL surface finish and by an average of 22%.

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.

Pinless FSSW of DP600/Zn/AA6061 dissimilar joints

AA6061 alloy sheets have been successfully spot-welded to dual-phase DP600 steel sheets with pinless friction stir spot welding method. The Box-Behnken design of experiments was implemented to arrange the tests. The individual and interaction effect of each process parameter on the lap-shear failure load of the joints was investigated. The maximum failure load of 4.4 kN was achieved at 1300 rpm rotational speed, 2000 kg axial force, and 10 s welding time. Microstructural features of the interfaces and phase evolution were studied by scanning electron microscope and X-ray diffraction, respectively. The bonding mechanisms at the joint interface are classified into two types: thick intermetallic layer (type I), and thin intermetallic layer with thick Zn–Al diffusion region (type II) in the aluminum/steel interface.