Dissimilar Materials Research Articles

Experimental analysis and optimization of friction welding parameters for joining dissimilar materials through design of experiments

Experimental analysis and optimization of friction welding parameters for joining dissimilar materials through design of experiments

Influence of Metal Surface Structures on Composite Formation during Polymer–Metal Joining Based on Reactive Al/Ni Multilayer Foil

Progressive developments in the field of lightweight construction and engineering demand continuous substitution of metals with suitable polymers. However, the combination of dissimilar materials results in a multitude of challenges based on different chemical and physical material properties. Reactive multilayer systems offer a promising joining method for flexible and low‐distortion joining of dissimilar joining partners with an energy source introduced directly into the joining zone. Within this publication, hybrid lap joints between semicrystalline polyamide 6 and surface‐structured austenitic steel X5CrNi18–10 (EN 1.4301) are joined using reactive Al/Ni multilayer foils of the type Indium–NanoFoil. The main objective is to examine possibilities of influencing crack initiation in the foil plane by variation of joining pressure and different metal surface structures with regard to geometry, density, and orientation. Thus, the position of foil cracks is superimposed onto the metal structure and associated filling with molten plastic is improved. Consequently, characterization of occurring crack positions as a function of joining pressure and metal structure, analysis of the composite in terms of structural filling and joint strength, as well as possible causes of crack initiation are evaluated.

Strengthening sandwich composites by laminating ultra-thin oriented carbon nanotube sheets at the skin/core interface

Strong, tough, and lightweight composites are increasingly needed for diverse applications, from wind turbines to cars and aircraft. These composites typically contain sheets of strong and high-modulus fibers in a matrix that are joined with other materials to resist fracture. Coupling these dissimilar materials together is challenging to enhance delamination properties at their interface. We herein investigate using a trace amount of carbon nanotube sheets to improve the coupling between composite skins and core in a composite sandwich. Ultra-thin (∼100 nm) forest-drawn multi-walled carbon nanotube (MWNT) sheets are interleaved within the skin/core interphase, with MWNTs aligned in the longitudinal direction. The mechanical behavior is characterized by end-notched flexural testing (ENF). With two MWNT sheets placed in the skin/core interphase, the following performance enhancements are achieved: 36.8 % increase in flexural strength; 127.3 % and 125.7 % increases in mode I & II fracture toughness values, respectively; and 152.8 % increase in interfacial shear strength (IFSS). These are achieved with negligible weight gain of the composite sandwich (0.084 wt% increase over the baseline sandwich without MWNT sheets). The finite element simulation results show that MWNT sheets enhance the skin/core coupling by reducing stress concentration, enabling the transition from catastrophic brittle failure to a stable ductile failure mode. The MWNT sheets interleaved sandwich composites are thus demonstrated to be stronger and tougher while providing electrical conductivity (4.3 × 104S/m) at the skin/core interface for potential de-icing, electromagnetic interference shielding, and structural health monitoring.

The effect of Sn interlayer on weld structure, intermetallic compounds, and joint properties of Al/Mg friction stir welding with ultrasonic assistance

ABSTRACT: The formation of intermetallic compounds (IMCs) is a primary factor that affects the welding joint between dissimilar materials. In this study, experiments were performed using Al/Mg friction stir welding (FSW) and ultrasonic vibration enhanced FSW (UVeFSW) with varying thicknesses of Sn interlayer. Detailed characterization and tests were conducted to explore the effect of Sn interlayer with or without ultrasonic vibration on weld surface morphology, macro-micro structure, generation of IMCs, and joint tensile strength. The study discusses the effect of ultrasonic vibration coupled with Sn interlayer and provides ideas for IMCs regulation when joining dissimilar materials. The study showed that adding a Sn interlayer cannot eliminate the generation of Al-Mg IMCs, but it can significantly reduce their thickness. Applying ultrasonic vibration with Sn interlayer can further reduce the thickness of Al-Mg IMCs and improve the interface microstructure from ‘IMC + matrix +IMC + matrix’ multilayer structures to simple IMCs structures. Furthermore, the highest joint strength was achieved when the Sn interlayer thickness was 0.1 mm during FSW. UVeFSW’s joint strength can be further improved with 0.05 mm and 0.1 mm Sn interlayer.

Advancing 4D printing through designing interlocking blocks: enhancing deformation uniformity in active composite structures

Interlocking assemblies have been explored to address large assembly and complex parts and are now integral to additive manufacturing (AM) for creating objects with dissimilar materials and multiple properties. 4D printing technology, which combines smart materials (SMs) with AM, aligns with this approach by enabling the creation of objects that can change shape or properties when exposed to external stimuli. As 4D printing trends towards strategically arranging active and passive materials for improved control and performance, challenges arise due to the limited compatibility of existing 3D printers with the required SM properties. To address this issue, interlocking blocks of dissimilar materials can be printed and then assembled into a desired shape. This work aims to generalize the applicability of the interlocking block assembly approach. This will be achieved by improving the deformation uniformity in a 4D multi-material interlocked assembly. This paper also addresses limitations that can occur due to the interfaces between interlocking blocks, such as lack of deformation and contact continuity. Thus, it will be a question of customizing the shapes of the blocks in the early stages of assembly generation, considering SMs and their potential transformations. Finally, this approach is illustrated with an example, shedding light on the practical implications.

Extrinsic-Riveting Friction Stir Lap Welding of Al/Steel Dissimilar Materials.

To obtain high-quality joints of Al/steel dissimilar materials, a new extrinsic-riveting friction stir lap welding (ERFSLW) method was proposed combining the synthesis advantages of mechanical riveting and metallurgical bonding. SiC-reinforced Al matrix composite bars were placed in the prefabricated holes in Al sheets and steel sheets, arranged in a zigzag array. The bars were stirred and mixed with Al sheets under severe plastic deformation (SPD), forming composite rivets to strengthen the mechanical joining. SiC particles were uniformly dispersed in the lower part of the welding nugget zone (WNZ). The smooth transition between the SiC mixed zone and extrinsic-riveting zone (ERZ) ensured the metallurgical bonding. The maximum tensile shear load of the joints reached 7.8 kN and the maximum load of the weld per unit length was 497 N/mm. The fracture occurred at the interface between the rivets and steel sheets rather than the conventional Al/steel joining interface. Moreover, ERFSLW can prolong the service life of joints due to three fracture stages. This method can be further extended to the welding of other dissimilar materials that conform to the model of "soft/hard".

Magnet-in-ferroelectric crystals exhibiting photomultiferroicity

Growing crystallographically incommensurate and dissimilar organic materials is fundamentally intriguing but challenging for the prominent cross-correlation phenomenon enabling unique magnetic, electronic, and optical functionalities. Here, we report the growth of molecular layered magnet-in-ferroelectric crystals, demonstrating photomanipulation of interfacial ferroic coupling. The heterocrystals exhibit striking photomagnetization and magnetoelectricity, resulting in photomultiferroic coupling and complete change of their color while inheriting ferroelectricity and magnetism from the parent phases. Under a light illumination, ferromagnetic resonance shifts of 910 Oe are observed in heterocrystals while showing a magnetization change of 0.015 emu/g. In addition, a noticeable magnetization change (8% of magnetization at a 1,000 Oe external field) in the vicinity of ferro-to-paraelectric transition is observed. The mechanistic electric-field-dependent studies suggest the photoinduced ferroelectric field effect responsible for the tailoring of photo-piezo-magnetism. The crystallographic analyses further evidence the lattice coupling of a magnet-in-ferroelectric heterocrystal system.

Friction Welding of ETP-Cu Plate to SS304L Round Bar: An Experimental Study on Asymmetrical Dissimilar Metal Joints

This article outlines the development and examination of the properties of an asymmetrical dissimilar metal joint produced using friction welding (FW). Friction welding involving dissimilar materials, specifically a 50 mm (length) × 45 mm (width) × 20-mm (thickness) electrolytic tough pitch copper (ETP-Cu) plate and a 12.5-mm-diameter SS304L rod, was carried out. The assessment of the asymmetrically welded components encompassed ultrasonic testing, high-pressure helium gas testing, leak testing, tensile testing, scanning electron microscopy, optical microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction analysis, hardness measurements, and elemental mapping via X-ray. Significantly, there was an observed increase in tensile strength, resulting in a joint efficiency of 86.50% compared to the ETP-Cu base material, following FW between an asymmetric ETP-Cu plate and SS304L rod. The study unveiled notable variations in the microstructure near the joint interface on the ETP-Cu material side. Intermetallic compounds, such as FeCu4 and Cu9Si phases, were detected within the reaction layer at the interface between ETP-Cu and SS304L, exhibiting a variable thickness ranging from 30 to 50 μm.

Diagnosis of Al-CFRTP TA-FSLW defect using acoustic emission signal based on SPWVD and ResNet

As one of the important development directions in modern railway and automobile, lightweight requires reliable connection technology of dissimilar materials. Thermal-assisted friction stir lap welding (TA-FSLW) is an available welding technology for the joining of dissimilar materials, which can solve the problems of physical and chemical properties in the welding process of dissimilar materials. Unfortunately, defects may occur during the welding process. This paper proposes a defect diagnosis method based on smooth pseudo Wigner-Ville distribution (SPWVD) and ResNet18 for Al-CFRTP TA-FSLW. Firstly, the acoustic emission (AE) signal and the temperature of the weld nugget are acquired by the AE sensor and thermography camera in the FSLW process. Then, the time–frequency domain features of AE signal are extracted by SPWVD, and the maximum temperature of the weld nugget is extracted by exponential moving average (EMA) from thermography. Moreover, the dataset is established by SPWVD features, maximum temperature of welding nugget, and several time–frequency features. Finally, the ResNet18-attention network is employed to classify welding defects and stages. The Al-CFRTP TA-FSLW experiments are carried out based on the proposed method. Experimental result indicates that the SPWVD spectrum can effectively extract the feature frequency of deep and shallow hole defects in the welding process. In the section of classification, the accuracy of the dataset with SPWVD features is improved by 2% to 4% compared to other methods, which demonstrates that the SPWVD feature is superior in defect feature extraction.

Interesting and Uninteresting Unknowns

This article explores the stark visual and epistemic contrasts between early modern representations of uncertain southern African spaces produced in the metropolitan Dutch Republic and the Cape Colony, respectively. It emphasizes the importance of metropolitan and colonial mapmakers’ different material interests in shaping their disparate visual cultures. Southern Africa was a heterotopia, viewed differently through metropolitan and settler eyes, and its visualization was interest-driven. Thus, the article argues, early modern representations of uncertain southern African topographies should be analyzed neither just as verisimilar descriptions nor as emptied or exoticized fantasies. Rather, the article proposes studying the epistemic and visual cultures of mapping with the perspective-dependent categories of interesting and uninteresting unknowns. Interesting unknowns tended to be illustrated in a straightforward, ostensibly representationalist manner, whereas uninteresting unknowns became sites for mapmakers to project delocalizing fantasies. Based on their dissimilar geopolitical perspectives and material interests, metropolitan Dutch and colonial creolized Cape mapmakers viewed different geographical unknowns as interesting or uninteresting. Thus, this article contends, scholars ought to pay more attention to the unique contexts that shaped their disparate depictions of the unknown.

Sikahyflex-Epoxy Mixed Adhesive’s Effect on the Aluminum-Composite Joint’s Shear Tensile Strength for the Automotive Industry

The automotive industry sector encounters challenges in the construction of connections between different materials. Hence, a breakthrough is needed in the automotive industry in manufacturing connections between different wall panel materials. Mixed adhesive materials for different materials are required and represent an innovation in the manufacturing process for joints of different materials due to the need for stiff and slightly ductile adhesives. This research aims to analyze the effect of using a sikahyflex-epoxy mixture adhesive in aluminum-composite joints on the shear tensile strength of the joints for the automotive industry. This research serves as an innovation in dissimilar material connection systems by developing the use of mixed adhesives and cocofiber aluminum-composite adherend materials with environmentally friendly and corrosion-resistant properties. The research material used aluminum 5083-cocofiber composite. The adherend surface was roughened employing sandpaper of #60, #80, and #150. The adhesive used the addition of sikahyflex adhesive to the epoxy adhesive with additional variations of 10%, 20%, 30%, and 40% sikahyflex. Connections between different materials with the single lap joint type refer to ASTM D1002. The roughness test results yielded the best roughness grade #150 on the surface of the aluminum adherend and coco fiber composite. The shear tensile test results by adding 40% sikahyflex adhesive, 0.4 mm adhesive thickness, and #150 sandpapering resulted in a 20% increase in shear tensile strength in the single lap joint of 2.51 N/mm2. The surface roughness enhanced the adhesive bond strength between mechanical interlocking adhesives and adherend. Meanwhile, the failure modes observed in macro observations included thin-layer cohesive failure, cohesive failure, two-stage failure, and stock-break failure modes. The SEM observation revealed that in the initial propagation of microcracking and voids, which mark the initial onset of adhesive failure, tearing took place, leading to a failure mode in the aluminum-composite coco fiber single overlap joint.

Laser welding of ultra-high strength steel rocket engine shell

The microstructure and mechanical properties of 30Cr3-30CrMnSiA ultra-high strength steel rocket engine shell welded joint were investigated in detail. The results indicated that the microstructure of the fusion zone was martensite of columnar and equiaxial due to the fast cooling rate of the laser welding. At the as-weld (AW) state, the average grain size of the 30Cr3 base metal was 4.63 μm, which was much smaller than that of the 30CrMnSiA base metal, which averaged 6.85 μm. After the post-weld heat treatment (PWHT), all the microstructures of the base metal, fusion zone and heat affected zone (HAZ) of 30Cr3 were tempered martensite. Meanwhile, at both AW and PWHT state, the tensile specimens of the welded joints of dissimilar materials were all fractured in the 30CrMnSiA base metal side at both 25 °C and 800 °C. After the PWHT, the tensile strength of 30CrMnSiA and 30Cr3 base metal at 25 °C were 1517.4 MPa and 1795.3 MPa, respectively. The welded joints of dissimilar materials by laser welding also showed excellent tensile properties at high temperature (800 °C), because of the small average grain size.

Interface crack analysis in 2D bounded dissimilar materials using an enriched physics-informed neural networks

This study explores the application of physics-informed neural networks (PINNs) to analyze interface crack problems within the context of elastic bimaterial fracture mechanics. Bimaterial interface cracks exhibit a distinct behavior compared to cracks in homogeneous materials, and this behavior often involves oscillatory phenomena that can pose challenges in numerical modeling. By employing neural networks for solution approximation, PINNs are meshless and are trained using batches of collocation points, which may be randomly or strategically sampled across the computational domain. To effectively capture the oscillatory singular behavior in the crack-tip regions, this paper introduces an enhanced PINNs formulation that enables the modeling of interface cracks without requiring any refinement near the crack-tip. The trainable parameters of the current PINNs are dynamically optimized throughout the training process to fulfill both the underlying differential equations and the associated initial/boundary conditions. One of the significant advantages of the present PINNs is that it uses enrichment functions to capture the behavior around the crack region, allowing for greater flexibility in handling irregular or complex crack paths. The method's accuracy and stability are validated across several benchmark examples.

Effect of Preheating and Post-Heating on the Microstructures and Mechanical Properties of TC17-Ti2AlNb Joint with Electron Beam Welding.

To enhance welding quality and performance, preheating and post-heating are usually employed on high-temperature materials, concurrently with welding. This is a novel technique in vacuum chamber electron beam welding (EBW). TC17 and Ti2AlNb alloys are the hot topics in aero-engine parts, and the welding of dissimilar materials is also a broad prospect. To settle welding cracks of Ti2AlNb, EBW with preheating and post-heating was investigated on TC17 and Ti2AlNb dissimilar alloy, which improved the manufacturing technology on high-temperature materials. The dissimilar joint no longer had cracks after preheating, which exhibited excellent welding stability and metallurgical homogeneity, and preheating and annealing had an important effect on mechanical properties. The joint strength after 630 °C annealing is higher than that of TC17 alloy base metal (BM) and other annealing temperatures, reaching 1169 MPa at room temperature and 894 MPa at 450 °C tensile condition. The joint plasticity after 740 °C annealing is equivalent to TC17 BM. EBW with preheating improved the microstructure characteristics and enhanced the plasticity of Ti2AlNb alloy weld and dissimilar joint, which would contribute to the application of Ti2AlNb alloy and Ti2AlNb dissimilar parts.

Design of dissimilar material joint for defect-free multi-material additive manufacturing via laser-directed energy deposition

Additive manufacturing technology has advanced beyond creating optimized features, from strengthening materials to make them lightweight to fabricating multi-material combinations that offer functionalities beyond the capabilities of individual materials. In this study, a lamination method for laser-directed energy deposition (LDED) is developed to achieve dense multi-material features, and a design that combines different and dissimilar materials is developed. To evaluate these novel developments, two materials—AISI 316L stainless steel and Inconel 625—are introduced. Tensile specimens, fabricated via multi-material additive manufacturing using LDED, are subjected to tensile tests that are recorded on video for digital image correlation. After the tests, fracture surface analyses of the fractured specimens are performed via scanning electron microscopy, and optical monitoring analyses are performed on the specimens that are not subjected to the tensile tests. The results indicate that the specimens demonstrate varied mechanical properties due to the influence of lamination direction and order, which affect the formation of critical cracks and pores.

Dual‐beam lasers meet challenges of the automotive industry

AbstractThe challenges of transport electrification require the adoption of new manufacturing techniques. Lasers excel in most difficult tasks due to their ability to deliver energy with great precision, and their temporal and spatial control. Dual‐beam, adjustable mode beam (AMB) technology enables the versatile spatial control of laser energy deposition, providing wide process windows for defect‐free welding and focal spot positioning. The AMB technology improves process quality and speed in dissimilar material welding, copper welding and in structural aluminum welding across many applications in the automotive industry – from the production of batteries and drivetrains to structural body parts.

A State-of-the-Art Review on Direct Welding of Polymer to Metal for Structural Applications: Part 1 — Promising Processes

Structural lightweighting through the effective use of multiple materials has received increasing attention for fulfilling today’s demands for environmental sustainability in transportation systems. Direct dissimilar material joining methods (versus, e.g., traditional adhesive bonding or mechanical fastening) have become increasingly desirable since they offer process simplicity, production efficiency, and hermetic sealing, among others. In this two-part article, we provide a critical assessment of the state-of-the-art research and promising direct dissimilar material joining techniques reported over the last decades, with a particular emphasis on their potential for structural applications in Part I. As such, recent advances in advanced joint design and modeling methods for enabling optimum joint design for jointability and joint performance are presented along with some detailed examples for demonstrating their potential impacts on industrial applications in Part II. Finally, recommendations on future research and development directions are outlined for supporting the industry’s drive towards multi-material lightweighting.

Microstructural evolution of a printed AISI 303 upcycled powder on a dissimilar substrate

Additive manufacturing for new constructions or repairing purposes may deal with the use of dissimilar materials. Hence, the influence of interface between the substrate layer and printed one is crucial. This study delves into the impact of printed layers on the microstructure and hardness of an upcycled AISI 303 alloy produced by Direct Energy Deposition. Chemical composition distribution, phase and grain size evolutions were studied, accompanied with microhardness measurements.Microscopic analysis through chemical composition mapping and using electron backscatter diffraction technique for crystallography analysis revealed that the interface structure is strongly affected by the distribution of chemical composition and the heat received from subsequent printing. That means, a dominant transformation of austenite to martensite/ferrite occurs at the first layer printed on the top of the substrate. This is confirmed by hardness measurements (442 ± 15 HV0.1). This dominance (global martensite/ferrite distribution of 42%) is attributed to the reduction of Cr, Ni and Mn contents in the first layer, caused by Marangoni convection currents. This study confirms that subsequent printing favors the evolution of martensite/ferrite to austenite (global distribution of 75%) and grain growth, leading to hardness decrease to around 295 ± 34 HV0.1, leaving small difference with the printed AISI 303 alloy with a hardness of 235 ± 18 HV0.1.

THE EFFECT OF FRICTION TIME VARIATIONS ON DISSIMILAR MATERIAL WELDING JOINTS AND HARDNESS VALUE USING A BAR-PLATE ROTARY FRICTION WELDING MACHINE

This research aims to determine the effect of variations in friction time on welded joints of dissimilar materials and hardness values. The method used is the friction welding method. One of the materials widely used in industrial products is mild steel AISI 1037 and stainless steel 304. One of the tools used is a bar-plate upright rotary friction welding machine. The parameters used are friction time variations of 25-35 seconds, 55-65 seconds and 115-125 seconds with a rotational speed of 2,484 rpm, friction pressure of 0.5 MPa, forging pressure of 0.7 MPa, forging time of 10 seconds. From the results of the connection several tests were carried out, namely liquid penetrant , macro observation and hardness test. The results of liquid penetrant testing and macro observations showed no influence on the welding area. The results of hardness testing have an influence on the hardness value. In the interface area, the friction time variation of 120 seconds has the highest hardness value of 161.67 VHN. The lowest hardness value in the interface area with a friction time variation of 30 seconds is 152.90 VHN. Where the longer the friction time, the hardness value also increases.

A Study on Heat Flow Affects on Multiplies Dissimilar Material Laser Beam Welding

A Study on Heat Flow Affects on Multiplies Dissimilar Material Laser Beam Welding