Dissimilar Metallic Materials Research Articles

Formation and strengthening mechanism of high entropy nugget for aluminum/steel resistance rivet welding

Resistance rivet welding (RRW) was a promising joining process for aluminum (Al) alloy and steel. The high entropy mixed nugget (HEMN) with the composition of Al0.8CoCrFe1.6Ni was obtained by introducing a high entropy alloy (HEA) rivet in RRW process. The high entropy played a significant role in facilitating the formation of solid solution. The HEMN microstructure exhibited a nanometer-sized weave-like structure caused by spinodal decomposition, comprising both BCC and B2 phases. The average hardness of the HEMN exceeded that of the Al/Steel mixed nugget, resulting in higher lap-shear strength and ductility. The analysis of strengthening mechanism demonstrated that the lattice misfit and order strengthening were the primary contributors. This study provided a novel strategy for joining dissimilar metal materials.

Numerical study of refill friction stir spot welding of dissimilar metallic materials using smoothed particle hydrodynamics (SPH)

Numerical study of refill friction stir spot welding of dissimilar metallic materials using smoothed particle hydrodynamics (SPH)

Joining dissimilar metals by additive manufacturing: A review

The demand for lightweight materials, site-specific properties, and customized features drives the need for joining components made from dissimilar materials. However, dissimilar welding poses challenges such as the formation of large heat affected zones and intermetallic compounds at the interface, leading to easy premature failure and cracking. In recent years, additive manufacturing (AM) of dissimilar metallic materials has gained popularity as a solution to these challenges, as evidenced by numerous review articles discussing various aspects of this field. However, a comprehensive review focusing on microstructural analysis at the joint interface of a wide range of materials combinations produced by AM has been lacking. This review aims to address this gap by providing an in-depth examination of microstructures and mechanical properties at the interface for various metal combinations. Furthermore, it delves into different processing approaches and the challenges associated with manufacturing dissimilar structures. This review serves as a valuable resource for beginners in the field, offering a thorough discussion and comparison of the reported results. The paper presents major conclusions and identifies outstanding issues for future investigations. By providing valuable insights crucial for the widespread implementation of dissimilar AM technologies, this analysis will assist current AM processing for dissimilar structures. It is particularly significant for understanding the microstructure at the joint interface of various miscible and immiscible dissimilar structures manufactured using different additive manufacturing techniques.

Cavitation resistance of explosively welded aluminium/steel joint

Explosion welding is an unconventional method of joining two dissimilar metal materials, mostly used to clad dissimilar materials or when some unusual geometries need to be joined. Some of the bimetal joints obtained this way have applications in special cutting tools, transition joints, propellers and turbine blades, and therefore it is important to know the wear resistance of welded joints. In this research, explosive Demex, based on ammonium nitrate and trinitrotoluene, was used to weld plates of aluminium alloy AW-2024 and steel 1.0216. The welding procedure was carried out in the configuration of parallel plates. The quality of the welded joint was inspected on samples cut out from the welded plate by the method of microscopic analysis on the cross-section and by an ultrasonic cavitation test. Materials erosion in the zone of the welded joint after each of 4 cavitation cycles was observed using an optical microscope and by monitoring the mass loss. The wear resistance of the created bimetal was analysed from the aspects of further exploitation.

Performance and failure analysis of perforated CFRP/aluminum alloy bonding and self-piercing riveting hybrid joints

This paper explores the new hybrid hole-drilled bonding and self-piercing riveting (HH-BR) connection technique to enhance the strength and overall performance of carbon fiber reinforced polymer (CFRP) and dissimilar metal materials at joint interfaces. The forming quality, mechanical performance, failure modes, and fracture characteristics of the CFRP and aluminum alloy joints utilizing the HH-BR procedure were analyzed in detail and compared with the joints of the hole-less adhesive-bonding self-piercing riveting (H-BR) and self-piercing riveting (SPR). At the same time, the effects of different rivet performance levels, overlap lengths, and various fiber orientation angles on joint performance were discussed. The results show that joints made by the HH-BR technique have a substantial advantage in terms of achieving superior mechanical performance and interlocking value. Firstly, HH-BR joints with bent rivets and torn fibers have connection strengths that are noticeably higher than those with CFRP laminate delamination or rivet pullout failure. The use of the HH-BR technique for joining CFRP/aluminum alloy culminated in reduced strength loss and higher energy absorption than H-BR and SPR joints, improving the joint's overall strength. Secondly, the interlock value between the rivet and the plate, is what essentially determines the strength of HH-BR joints, especially evident in connections with 0°/90° fiber orientation and more overlap lengths. The results also show that there is a strong relationship between the height of the rivet head and the joint's mode of failure, and the height of the rivet head is affected by the rivet force. Furthermore, the interlock value's magnitude, the joint's remaining bottom thickness, and the metal material's capacity for plastic deformation are all directly correlated.

Evaluation of Laser Lap Weldability between the Titanium Alloy Ti-6Al-4V and Aluminum Alloy 6060-T6

This work investigates laser weldability between non-ferrous dissimilar metallic materials, specifically the aluminum 6060-T6 alloy and titanium Ti-6Al-4V. These materials are used in several engineering applications, including aerospace. In a simple lap joint configuration, these were welded with a pulsed Nd:YAG laser, with direct incidence on the titanium piece. Preheating and post-weld heating were introduced to mitigate cracking issues. Based on the primary experiments, the main variables were the peak laser power, which varied between 60 and 70%, and the number of beads (a single bead and double beads). The quality of the welds was assessed via uniaxial tensile tests, subjecting the joint to shear loading. Additionally, SEM micrographs were obtained to analyze the quality of the fusion between the dissimilar alloys. The higher strength of the welded samples achieved was 90 MPa, which is close to the reported value for the aluminum base material. A fracture occurred near the weld bead in the heat-affected zone (HAZ). The observed microporosities and cracks explain the lower value as compared to the base material. Although these were mitigated through the thermal cycle strategy employed and the shielding gas, they were not entirely avoided.

The morphology and evolution in Al-Cu and Al-Fe magnetic pulse weld interfaces characterized through phase-contrast micro-tomography

Magnetic Pulse Welding (MPW) facilitates the permanent joining of dissimilar metallic materials through the sudden impact generated by a magnetic pulsed field. The process can introduce distinct morphological features at the interface of bi-material joints, which subsequently affect the joint’s quality and durability. This article delves into the investigation and quantification of various interfacial morphologies in Aluminum/Copper and Aluminum/Steel joints, using high-energy phase-contrast synchrotron micro-tomography. Surface topography is extracted from 3D tomographic datasets between dissimilar materials, enabling a comprehensive comparison between different material pairings and various locations within the weld. The study analyses and compares the roughness parameters of these surfaces. Moreover, it describes the interface’s waves and vortexes through diverse morphological metrics, encompassing their shape and size. The results provide evidences that vortexes evolve in three dimensions, with lateral growth and collapse. The waves and vortexes shapes promote material interlocking, increasing the contact area between the dissimilar materials by up to 20%. The interface morphology of Al/Cu joints exhibits higher roughness and a greater number of vortexes compared to Al/Fe joints. Lastly, the findings reveal the presence of interface damage in the form of pre-existing discontinuities.

Nanoscale phenomena during wetting of copper on nickel-based superalloy: A molecular dynamics study

Joining of dissimilar metallic materials such as Inconel alloys and steel by vacuum brazing with copper (Cu) filler metal is highly desirable in a wide range of applications, for example, in construction of rotors for high-speed electrical motors. However, experiments have shown poor wettability of Cu on IN718 during vacuum brazing. In this work, molecular dynamics (MD) simulations are performed to study nanoscale interfacial phenomena that occur during brazing of IN600 and IN718 with steel using Cu. Hybrid potentials data is verified using density function theory (DFT) based energy calculation and melting point test models. The results show that IN600 coheres well with liquid Cu, whereas Niobium containing IN718 exhibits inhibited diffusion of atoms from the Inconel alloy into the liquid Cu. Additionally, the simulations show that liquid Cu atoms diffuse well into the precipitate (γ′′ phase) in IN718 but barely diffuse into the parent γ phase.

Enhanced strength-ductility synergy of laser additive manufactured stainless steel/Ni-based superalloy dissimilar materials characterized by bionic mechanical interlocking structures

The unique mechanism of toughness enhancement found in natural materials has served as inspiration for the development of a new generation of dissimilar metal materials (DMMs). Here we present a bionic mechanical interlocking structure strategy that stainless steel 316L and Inconel 625 DMMs with an enhanced strength-conductivity trade-off processed by laser additive manufacturing (AM), possessing an ultimate tensile strength of 675.64 MPa, and a uniform elongation of 33.6%. The incompatible deformation between SS316L (plastic deformation) and IN625 (non-deformation) contributes to overcoming the strength-ductility trade-off. The integration of alternating soft and hard non-uniform structures plays a pivotal role in effectively absorbing and dissipating the energy introduced by external loads during crack propagation. This geometric arrangement and multilevel structure at the interface notably reduces the effective stress intensity factor along the crack path, leading to added resistance against loading. The multi-strengthening mechanism coupled with the heterogeneous deformability gives the material excellent strength-ductility synergy, especially the bionic mechanical interlocking structure extending the crack expansion path, which helps to avoid premature failure of weak interface layers. These findings will provide new insights into the controlled design of high-performance DMMs, which highlights the potential to inherit merits from constitutive materials for better strength-ductility combinations.

Direct ink writing of porous Fe–Ti6Al4V and Fe-Inconel 718 bimetallic structures

Additive manufactured bimetallic structures provide site-specific functions by joining two metallic materials in the designed area, offering customized solutions for biomedical and engineering applications. However, cracking, delamination, or cross-contamination frequently occurs at the joint between two dissimilar metallic materials due to their different thermal properties. In the paper, porous bimetallic structures made of biomedical materials (Fe, Ti6Al4V, and Inconel 718) for bone implants are fabricated via direct ink writing (DIW) with a dual syringe system. After subsequent heat treatment, the original shapes of the bimetallic structures are well-preserved, and the shrinkages of the two materials are equalized by adjusting the sintering temperature. All joints are free of cracks and delamination, and the material deposition sequence has no impact on them, according to microstructural analyses of the interface. The pores created by binder pyrolysis and metallic powder sintering are necessary for bone growth, cell migration, body fluid flow, etc. The Fe–Ti6Al4V and Fe-Inconel 718 bimetallic structures have better mechanical properties than the Fe structures and can perform multiple functions that are challenging for monometallic implants.

Laser Powder Bed Fusion of Dissimilar Metal Materials: A Review

The laser powder bed fusion (LPBF) technique is used to manufacture complex and customised components by exploiting the unique advantages of two types of metal materials to meet specific performance requirements. A comprehensive overview of LPBF-processed dissimilar metal materials, a combination of different single metals or alloys, is developed. The microstructure in the fusion zone and the corresponding mechanical properties of LPBF-processed dissimilar metal materials are summarised. The influence of processing factors on the mechanism of defect formation, wetting properties and element diffusion behaviour at the interface between different materials and their typical cases are scientifically investigated in detail. Particular attention is paid to energy input, Marangoni convection and interfacial bonding behaviour. The underlying science of the metallurgical structure and properties of the LPBF-processed dissimilar metal materials is revealed. The build quality and efficiency could be further improved by designing machine structures and predicting the process-property relationship. This review provides a significant guide for expanding the industrial application of LPBF-processed dissimilar metal materials.

A Novel Low-Profile Self-Expanding Biodegradable Percutaneous Heart Valve Frame That Grows with a Child

According to rough estimates, one in every 125 newborns born in the United States has a congenital cardiac abnormality that must be repaired. With the recent development of new biomaterials and innovative treatment methods, percutaneous cardiac valve replacement has been considered as an alternative to surgical procedures. While percutaneous heart valve replacement is a relatively new procedure with a few commercially available devices, the devices are not sufficiently low-profile, and do not grow with the child. To address this issue, a novel low-profile growing percutaneous pediatric heart valve frame made of two types of unique metallic biomaterials (supere lastic nitinol and biodegradable iron) has been developed through this study. The developed pediatric heart valve frame has an innovative mechanism that will expand its diameter by disconnecting biodegradable metals, enabling the growth of the device with the surrounding tissue in the cardiac space. The thermally treated iron wires show stable and gradual degradation characteristics, showing approximately 7.66% for both wires treated under 350 and 450 °C. Polymer-coated wires show a degradation range of 4.96 to 5.55% depending on the type of coating. Degradation test results show the predicted 9–23 months of degradation depending on the type of surface treatment (e.g., thermal treatment, polymer coating), which is a suitable range when compared with the theoretical arterial vessel remodeling process period in the human vascular system. Radial forces calculated by finite element analysis and measured by mechanical testing matched well, showing 5–6 N with a 20% diameter reduction considering the deployed valve frame in the heart. Biocompatibility study results demonstrated superior cell viability in thermally treated iron wires after 3 days of cell culture and showed rarely found platelets on the surface after 3-h blood exposure tests. Prototype devices were successfully fabricated using optimized advanced joining processes for dissimilar metallic materials such as nitinol and iron. This study represents the first demonstration of self-expanding and biodegradable percutaneous heart valve frames for pediatric patients that grow with a child.

Experimental Investigation of Efficiency and Deposit Process Temperature during Multi-Layer Friction Surfacing

Multi-layer friction surfacing (MLFS) follows the principle of the friction surfacing (FS) process, which is an established solid state coating technology for similar and dissimilar metallic materials. With this approach, the deposition of a consumable material on a substrate is enabled via friction and severe plastic deformation (SPD), processing the material below its melting temperature. The focus of the present study lies on the investigation of the temperature distribution during MLFS deposition. The measurements show that the temperature within the stack tends to be slightly higher on the advancing side. Additionally, the deposition behavior, i.e. deposition rate and consumable stud consumption rate, was investigated. Along MLFS stack height, deposition efficiency tends to sightly decrease, shown by decreasing layer thickness and increased length of remaining consumable studs. Overall, MLFS is highly repeatable for multiple layers and presents stable deposition conditions. Additionally, the technique has a comparatively low heat input to the substrate and the already deposited material.

Tool wear mechanisms and effects on refill friction stir spot welding of AA2198-T8 sheets

Refill Friction Stir Spot Welding (refill FSSW) is a method for joining similar and dissimilar lightweight metallic materials or thermoplastic polymers. The technique produces welds that feature suitable mechanical properties with advantages such as the possibility of industrial scalability and automation. Still, some challenges need to be overcome in order to increase the adoption of this technique in industry. Tool wear is a key issue for friction-based processes, since it impacts the process costs and quality of the welds. In this study, a total of 2350 welds of AA2198-T8 sheets were performed and the effect of wear on probe and shoulder was investigated. While the probe did not suffer any considerable wear after this number of welds, the shoulder underwent wear in different areas, with distinct wear mechanisms. Adhesive wear and plastic deformation were determined as the primary damage mechanisms affecting different areas of the shoulder. Mechanical testing of selected welds has shown a trend towards reduction in the lap shear strength (LSS) as a function of tool wear. Macrostructural analysis of welds' geometrical features shows that profile changes at the shoulder due to wear led to a trend of reduction in stirred zone area and, consequently, joints’ LSS. Modifications in the worn shoulder profile were suggested as possible causes for changes in hook height, which was identified as a further determining factor to the observed reduction in LSS. Still, all tested welds surpassed the minimum lap shear strength standard requirements for aeronautical applications.

Combined experimental-numerical analysis of the temperature evolution and distribution during friction surfacing

Friction surfacing (FS) is a solid state coating technology for similar and dissimilar metallic materials. The coating of the substrate with a consumable material is enabled due to frictional heat and plastic deformation and is performed below the materials' melting temperature. In this work, the spatio-temporal temperature field during FS is investigated within the substrate via a combined experimental-numerical approach. The study presents a robust and efficient thermal process model accounting for the contributions of friction and plasticity as heat input. The geometry of the applied heat source is dependent on the deposit geometry and the evolving flash. Extensive spatial temperature measurements for a dissimilar aluminum alloy combination are used in order to identify the required input parameters and to validate the model. The process temperature profiles for varied process parameters, such as axial force, rotational speed and travel speed as well as substrate thickness and backing plate material are systematically investigated, where experimental and numerical results are in good agreement. Deviations are in particular associated with possible experimental scatter and unknowns regarding the exact position of the measurement as well as modeling assumptions in terms of the heat source geometry. Overall, the detailed comparisons illustrate that the developed numerical model is able to obtain the temperature evolution and distribution during FS deposition with acceptable accuracy for a wide range of process conditions.

Case Study About Resistance Projection Welding of Aluminized Steel Parts

Resistance projection welding is a non-polluting mechanized process used to obtain an assembly between similar or dissimilar metallic materials. The main advantages of this welding process are the possibility to achieve many different welded points at the same time and the long life of the electrodes compared to the spot-welding process. The paper analyses the effects of thin aluminium coating existing on mild steel parts of on the correct formation of welding points when assembling moulds for the manufacture of baking bread. From optical and electron microscopy analyses it resulted that some adjacent welded points show an interrupted fusion line, sprinkled with elongated islands of aluminium-rich compounds. The paper presents the effect of changing the values ​​of the welding parameters on the weld spot size, in correlation with the Al-rich inclusions that appear on the weld fusion zone. The best results have been obtained when the welding parameters values were the follows: electrode pressure of 2.6 bar, welding power of 19.18kVA and welding time of 7ms. The problems that occur when electric resistance welding of parts with aluminium coating have been highlighted, being useful for specialists who make products using this welding process.

An investigation of the mechanical properties and bonding mechanism of Ti/Al-laminated composites fabricated by ultrasonic consolidation

Foils such as 1100 aluminum and TC4 titanium were used as matrix materials for ultrasonic consolidation test of dissimilar metal materials, and the samples of Ti/Al-laminated composites were prepared. The effect of amplitude and static pressure on the interfacial bonding strength of Ti/Al foil was studied by adhesion test. The mechanical properties of Ti/Al-laminated composites were tested by electronic universal testing machine. The microstructure of Ti/Al foil interface was observed by transmission electron microscope. The results show that ultrasonic consolidation can achieve a good bonding interface of Ti/Al foil, and the bonding strength of the interface increases first and then decreases with the increase of static pressure, and increases monotonously with the increase of amplitude. The optimum adhesion strength is 58.08 N cm−1. The high temperature deformation constitutive model of Ti/Al-laminated composites is established and verified. The Ti/Al interface has metallurgical bonding, and the inner microstructure of Ti/Al matrix is obviously refined. The surface of titanium foil has formed nanocrystalline.

Microstructural Evolution and Growth of Intermetallic Compounds at the Interface between Solid Cast Iron and Liquid Al–Si Alloy

Compound casting has received a great deal of attention as a useful method for fabricating a single complicated part from dissimilar metallic materials. For example, in the case of automobile cylinder blocks, research is being carried out to compound cast iron with aluminum alloys. In order to manufacture such as composite parts, it is essential to control the intermetallic compound formed at the interface between two metals. In this research, the type and growth behavior of compounds formed at the interface between cast iron and aluminum, or Al–Si alloy, were investigated. It was observed that the Al5Fe2 phase was mainly formed at the interface between the pure aluminum melt and the solid cast iron, and the thickness of the interfacial compound increased proportionally with increasing contact time. On the other hand, more complex phases were formed at the interface between the Al–Si alloy melt and the solid cast iron. In the case of a specimen having a contact time of 10 min, Al4.5FeSi, Al8Fe2Si and Al5Fe2 phases appeared to occupy the largest portion of the interfacial compound region. The total thickness of the interfacial compounds also increased in proportion to the contact time.

Modelling of intermetallic layers formation during solid-liquid joining of dissimilar metallic materials

Joining of dissimilar metallic materials gives rise to the production of components with improved properties. At the joint interface, the formation of brittle intermetallic layers might deteriorate the component application. Therefore, its formation and growth must be well understood and carefully controlled. Numerical simulations assist in the determination of processes parameters to obtain the desired bond characteristics. In solid-liquid joining processes, the melt movement plays an important role und must be accounted in the simulations. In this paper, a mathematical model at the continuum scale is used for the description of the interface formation during solid-liquid joining. The description of convection and advection of the molten alloy and the dissolution of the solid substrate are of interest. The substrate dissolution into the melt alters the local composition of the molten alloy, leading to precipitation of intermetallic compounds on the substrate surface during the solidification process. To account for these phenomena, convection heat transfer with phase transformation and diffusion and reaction at the solid-liquid interface are considered in the mathematical model that is based on conservation equations of mass, momentum, energy and species. The different scale problem is solved by applying a dynamic mesh refinement at the interface to accurately solve the intermetallic layer growth. The model was implemented in OpenFoam® and simulation results for the intermetallic layer thickness as a function of solid substrate temperature (Ts) for compound casting between initially liquid Al and a solid Cu substrate are presented. In general, for Ts initial value ranging from 400 to 700 °C while keeping the initial Al melt temperate at 750 °C, the intermetallic layers thickness increases as Ts increases.

Influence mechanism of process parameters on the interfacial characterization of selective laser melting 316L/CuSn10

Bimetallic structures can combine the performance of dissimilar metal materials to meet the multifunctional requirement in industrial solutions. In this paper, steel-bronze bimetallic structures were fabricated via self-developed multi-material selective laser melting (SLM) equipment. In order to investigate the influence of laser power, scanning speed, and hatching space on the interfacial characterization, three factors and five levels of orthogonal experiments were performed on twenty layers of CuSn10 tin bronze after forming the 316 L stainless steel. Optical microscope (OM), large depth field microscope, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), tensile properties, electron backscattering diffraction (EBSD) and nanoindentation were used to characterize these bimetallic structures to validate the impact from process parameters. The large depth field microscope revealed protrusions at the steel/bronze interface, and its height increased and then decreased with increasing volumetric energy input. Besides, the generation of interfacial defects is related to the interfacial process parameters, and it is found that the types of defects are mainly classified as holes and cracks. Insufficient energy will cause cracks in the horizontal direction and then lead to bonding failure. Conversely, higher energy input will generate microcracks in the vertical direction. The defects near the interfacial region are the main factors affecting the ultimate strength of the bonding strength. As a result, the steel-bronze bimetallic structure displays optimal joint ultimate strength of 459.54 ± 3.08 MPa with elongation of 5.23 ± 0.65%, and minimum joint ultimate strength of 199.02 ± 0.56 MPa with elongation of 1.70 ± 0.22%. Their fracture morphology also exhibited gully-like and fan-shaped features, respectively. Additionally, the EBSD results show that there are fine grain regions appeared in the interfacial region, which helps increase the average nano-hardness of the interfacial region. This study provides a reference for the influence of process parameters on the interfacial characterization and mechanical properties of steel-bronze bimetallic parts prepared by selective laser melting.