Search Results (19)

The incorporation of multi-material design (MMD) to achieve lightweight vehicles requires Friction Stir Spot Welding (FSSW) to join steel with aluminum, magnesium, or composites. This study investigates the mechanisms, challenges, and performance of FSSW in MMD based on the information available in the literature. It also explores the effect of FSSW tool geometries and design on the spot weld formation and mechanical strength. Larger shoulder and pin diameters increase heat generation during welding. A concave shoulder profile produces a stronger weld compared to flat and convex profiles due to its ability to trap materials and transfer materials to the sheet interface efficiently for the development of a sound weld. Grooves such as Fibonacci and involute, and threads on P-FSSW and R-FSSW tools, also contribute to effective material flow during welding, hence assisting in heat generation. This review also provides recommendations on tool design for FSSW, P-FSSW, and R-FSSW. Full article

Ultrasonic spot welding (USW) represents one of the unique solid-state joining methods for lightweight materials such as magnesium alloy and aluminum alloy. However, the sonotrode vibration may have a detrimental impact on the sheet material and the existing welds, depending on the component geometry and vibration frequency. In this study, a modal analysis tool based on steady-state dynamics was developed for ultrasonic spot welding which features a cyclic load applied to the sheets during the joining process. Through predicting relative motion and shear stress at the faying surfaces, coupon geometry and weld spacing are identified as two major factors that affect the welding reliability and joint quality in USW. The model was validated via welding experiments on aluminum alloy and magnesium alloy and relevant characterization of temperature distribution, joint strength as well as fracture location. Full article

The present work proposes a suitable approach for predicting ductile fracture in a new joining process by plastic deformation called hole hemming. This process creates a combined form- and force-fit joint and enables the joining of lightweight materials with varying formability without requiring heating or auxiliary elements. In this process, the joinability of materials is limited by the occurrence of fracture in the outer sheet, highlighting the crucial need to accurately predict its damage during the process design phase. In this study, five different fracture criteria, including the McClintock, Rice–Tracey, Normalized Cockroft–Latham, and Brozzo and Modified Mohr–Coulomb (MMC) criteria, are examined during the joining of a challenging combination of lightweight materials (aluminum AA6082-T4 and magnesium AZ31). These criteria are calibrated by a hybrid experimental–numerical method using three tests with distinct stress states. These criteria are then implemented into the finite element model of the hole hemming process, utilizing an appropriate user subroutine. The results show that the flange edge of the outer sheet is the most prone region to fracture during the joining process, and a criterion must be able to model the fracture behavior of the material from uniaxial tension to shear to accurately predict fracture in this area. Among the examined criteria, only the MMC criterion was capable of such modeling and accurately predicted the critical displacement of the punch in the hemming stage with a negligible error (about 1%). On the other hand, the prediction accuracy of the other criteria varied significantly depending on the calibration test, resulting in errors ranging from 8.6% to 75.5%. The error of 8.6% was achieved with the Normalized Cockroft–Latham criterion calibrated by a uniaxial tension test. Thus, based on the results, the MMC criterion is recommended for ductile fracture prediction in the hole hemming process, offering valuable insights to assist in process design. Full article

Friction stir welding (FSW) is a solid-state welding process capable of joining a wide range of light metals. However, liquation and solidification may occur during joining of dissimilar metals which leads to eutectic formation. This article aims to discover the influence of tool rotation speed on the formation of eutectic structure during friction stir welding of aluminum to magnesium. To do so, friction stir welding was performed at 600 and 950 rpm to join pure aluminum and ECO-AZ91 magnesium alloy in a lap configuration. In order to investigate the influence of the welding speed, the welding speeds of 23.5 and 37.5 mm/min were also chosen. Scanning electron microscopy (SEM) was used to study the microstructure of the joints. A shear-tensile test was used to evaluate the joints’ strengths. The fracture surfaces were also studied by SEM. The results revealed that changing the rotation speed directly affects the eutectic formation, whereas the welding speed had no influence. A lower rotation speed resulted in a thin, continuous intermetallic layer, whereas a higher speed led to the formation of a massive Mg-Al₁₂Mg₁₇ eutectic microstructure. The formation of eutectic, as an indicative of liquation, may affect the material flow during the process due to decreasing the friction coefficient between the tool and material. The macrostructure analyses showed that the phase evolution as well as the mechanism of material flow are highly affected by liquation. Full article

Electrical-current-assisted friction stir welding (EA-FSW) is a procedure developed for the joining of similar and dissimilar materials. EA-FSW is a newly invented solid-state process to increase welded components’ efficacy in various applications, such as marine structures. EA-FSW joints have investigated the dissimilar joints on aluminum–magnesium, aluminum–steel, and polymer-to-steel. Similar joints have been performed on aluminum, magnesium, and steel. The main parameters that affect the temperature of the nugget in EA-FSW are electrical current and tool rotational velocity. This review paper presents the fundamental principle of EA-FSW, its processes mechanism, and various types of tools, and discusses the different joints that EA-FSW welded. The effect of electrical current on the quality of similar and dissimilar joints is discussed. The simulation process and detailed modeling of the EA-FSW process are discussed in the last section. Full article

Research activities considering lightweight design are dedicated to substituting classic mild steels by light metal alloys. Magnesium is especially promising due to its beneficial strength–density ratio, but its industrial use is still limited due to, e.g., unfavorable corrosion properties. Thus, a methodology for applying thin aluminum layers to magnesium base material by hot roll cladding has been developed. This paper characterizes the compound via peel tests, lap shear tests, Nakajima tests and deep drawing tests, thus identifying beneficial process parameters. It proves high interlaminar adhesion strength and significantly better formability then the bare magnesium core material. Full article

Friction stir welding (FSW) has now reached a technological impact and diffusion that makes it a common joining practice for several classes of metallic materials. These include light alloys (aluminum, titanium, magnesium), steels, and other metallic alloys. In addition, the combination of FSW with pre- or post-welding heat treatments or plastic deformation, such as cold rolling (CR), can favor minimal necessary plate thicknesses and induce effective alloy strengthening mechanisms that make the FSW joint lines as plate reinforcing zones. Process parameters, such as pin rotation and transverse speed, can be tuned to optimize the mechanical properties of the resulting joint. This work presents a microstructural study of the mechanical response of different sequences of heat treatment, FSW, and CR in a non-age hardened Al-Mg AA5754 alloy. By using polarized optical microscopy and microhardness tests, two FSW conditions were used to fabricate a joint; and were than subjected to different sequences of heat treatment and cold rolling. The results suggest that FSW conditions have a limited effect on the microstructure, while microhardness profiles show a higher variability of the different datasets related to the low welding speed investigated. Full article

Dissimilar friction stir spot welds (FSSW) between the magnesium and aluminum alloys are joined, using a novel approach called refill friction stir spot welding. The present work aims to evaluate the macrostructural and mechanical properties of refill friction stir spot welded AZ31B and AA 6061-T6 alloys in two combinations, i.e., identical Mg-to-Mg and dissimilar Mg-to-Al joints, and the results are compared with the results obtained in conventional friction stir spot welding. The hardness profiles of the similar welds had the appearance of a W-shape, and the Thermo mechanically affected zone and heat-affected zone of both methods had lower hardness values than the rest of the weld. Along with the interface between the aluminum and magnesium sheets, a thin intermetallic compound layer of Al₁₂Mg₁₇ has been identified, which has led to an increase in hardness. The static shear strength of both similar and dissimilar refill spot friction welds was much greater than that of traditional spot friction welds. In both similar and dissimilar spot friction welds, two distinct failure scenarios are discovered. Full article

In engineering applications, such as automobile, marine, aerospace, and railway, lightweight alloys of aluminum (Al) and magnesium (Mg) ensure design fitness for fuel economy, better efficiency, and overall cost reduction. Friction stir welding (FSW) for joining dissimilar materials has been considered better than the conventional fusion welding process because of metallurgical concerns. In this study, dissimilar joints were made between the AA6061 (A), AZ31B (B), and AZ91D (C) combinations based on the varying advancing side (AS) and retreating side (RS). The dissimilar joints prepared by the FSW process were further characterized by tensile testing, impact testing, corrosion testing, fracture, and statistical and cost analysis. The results revealed a maximum tensile strength of 192.39 MPa in AZ91 and AZ31B, maximum yield strength of 134.38 MPa in a combination of AA6061 and AZ91, maximum hardness of 114 Hv in AA6061 and AZ31B, and lowest corrosion rate of 7.03 mV/A in AA6061 and AZ31B. The results of the properties were supported by photomicrographic fracture analysis by scanning electron microscopy (SEM) observations. Further, the performance of dissimilar joints was statistically analyzed and prioritized for preference by similarity to the ideal solution (TOPSIS) method. Full article

The Refill Friction Stir Spot Welding (RFSSW) process—an alternative solid-state joining technology—has gained momentum in the last decade for the welding of aluminum and magnesium alloys. Previous studies have addressed the influence of the RFSSW process on the microstructural and mechanical properties of the AA6061-T6 alloy. However, there is a lack of knowledge on how the tool wear influences the welding mechanical behavior for this alloy. The present work intended to evaluate and understand the influence of RFSSW tool wear on the mechanical performance of AA6061-T6 welds. Firstly, the welding parameters were optimized through the Designing of Experiments (DoE), to maximize the obtained ultimate lap shear force (ULSF) response. Following the statistical analysis, an optimized condition was found that reached a ULSF of 8.45 ± 0.08 kN. Secondly, the optimized set of welding parameters were applied to evaluate the wear undergone by the tool. The loss of worn-out material was systematically investigated by digital microscopy and the assessment of tool weight loss. Tool-wear-related microstructural and local mechanical property changes were assessed and compared with the yielded ULSF, and showed a correlation. Further investigations demonstrated the influence of tool wear on the height of the hook, which was located at the interface between the welded plates and, consequently, its effects on the observed fracture mechanisms and ULSF. These results support the understanding of tool wear mechanisms and helped to evaluate the tool lifespan for the selected commercial RFSSW tool which is used for aluminum alloys. Full article

Friction stir welding (FSW) is a process originally developed for joining light materials, such as aluminum and magnesium, as an answer to their poor weldability by conventional fusion processes. In Colombia, the technique has been studied but its industrial implementation is uncommon, due to the high cost of specialized machinery and the unfamiliarity with the technique of local industries. This article presents an implementation case study of FSW on a 6082-aluminum alloy train component from Metro de Medellín (MdM), aiming to establish the component design changes required to accommodate the FSW process, and conventional machines available in the local area which may be available for welding. Additionally, a simple comparison was made between the cost of this approach versus the manufacturing strategy currently used for the selected component. Initially, welding forces were measured when performing the seam on the selected component using an FSW machine. This data was then used to downselect the local milling machines with these capabilities. A simple but specific tool was designed for the geometry of one of the component features. Finally, a prototype was fabricated, and weld samples were obtained, polished, etched, and examined using a microhardness machine and an optical microscope. Results show a good opportunity for the execution of simple components with uniform geometries, which can be carried out using locally available machinery because they do not surpass their maximum loading capacity, the welds do not present visible discontinuities, and an average hardness of 69.5 HV and mechanical efficiency of 95% can be achieved. Additionally, the manufacturing process is around 30% cheaper compared to traditional methods, making the application viable, economically speaking. Full article

In this study, AA 6063 aluminum was joined using Tungsten Inert Gas (TIG) welding with a butt joint. The ER-5356 filler metal feeding method is used intermittently to find its effect on weld geometry, mechanical properties, microstructure, and chemical composition. The dimensions of the specimens used in this study were 120 mm × 50 mm, with a thickness of 3 mm. The ratio used is the configuration of the feed time and delay time. The length ratio of wire filler is varied from a ratio of 4 to 6. The top bead width and back bead width decreased by 17.66% and 40.33%, respectively. At a ratio of 6, it has the largest cross-sectional area of 295.37 ± 27.60 mm². The results show that the general tensile strength was proportional to the ratio, but the difference was not significant, only around ±8 MPa. The microstructure formed in each weld has different characteristics; conversely, grains with a relatively coarse structure have decreased hardness values. The chemical composition test shows that the length ratio of filler metal feed directly correlates with magnesium’s average weight content, where the weight content of magnesium value tends to be homogeneous in all areas of weld metal (WM). Full article

The 1060 aluminum and T2 copper were joined by the pulsed double electrode gas metal arc welding (DE-GMAW) brazing method by using four types of filler wires, namely pure aluminum (Al) ER1100, aluminum-magnesium (Al–Mg) ER5356, aluminum-silicon (Al–Si) ER4043, and Al–Si ER4047, respectively. The effects of different types of filler wires on intermetallic compounds, microhardness tensile strength, and conductivity of joints were investigated. The results showed that a lot of brittle intermetallic compounds laying in the copper side brazing interface zone were generated using pure Al, Al–Mg, and Al–Si filler wires, which caused the change of microhardness, tensile strength, and the conductivity of joints. Meanwhile, with the increase in Si elements contents for Al–Sifiller wires, the thickness of the intermetallic compound layers decreased obviously, which was only up to 3 µm and the conductivity of the joints decreased. In addition, the microhardness, tensile strength, and the conductivity of the joints, when using Al–Sifiller wires, was higher than that using pure Al and Al–Mg filler wires. Hence, in comparison to the pure filler wires and Al–Mg filler wires, the Al–Si filler wires were more suitable for Al–Cu joints by DE-GMAW as Si element content was lower. Full article

Brittle intermetallic phases are formed when steel and aluminum are joined. Therefore, it is difficult to use this combination of materials when applying the multimaterial design in the construction of load-adapted and weight-adapted structures. In order to largely avoid the formation of these brittle phases, joining processes based on diffusion processes, such as composite forging, depict a good solution approach. The materials are joined in a solid state. Furthermore, zinc additives are used to create the joint. Zinc forms a compound with both steel and aluminum without the formation of brittle phases. By combining the composite forging process with zinc additives, strength values of 26 N/mm² can be reached. This is higher, in comparison to former investigations of resistance spot welded and clinched joints. The joint properties depend on the composition of the zinc interlayer. Small amounts of magnesium in the zinc interlayer affected the strength and ductility values. While the strength decreased by about 30% in contrast to the zinc layer without magnesium, the ductility increased by 60%. This effect was probably due to the metallurgical impact of the alloying elements on phase formation, as could be shown by energy dispersive X-ray spectroscopy (EDX) analyses of the joint zones. Thereby, it was shown that the brittle intermetallic phases are located only in small areas. Full article

5A06 Aluminum (Al) alloy and AZ31B magnesium (Mg) alloy with 20 mm thickness were successfully butt joined by friction stir welding. In order to control the composition of Al and Mg alloys along thickness direction, an inclined butt joint was designed in this study. The microstructure and phase identification at the interface of Al/Mg joints were examined using scanning electron microscopy with an energy-dispersive spectroscopy and Micro X-ray diffraction. The results indicated that there were two different formation mechanisms of intermetallic compounds at the interface of thick plate Al/Mg joint. The first was constitutional liquation, and eutectic structure consisting of Al₁₂Mg₁₇ and Mg solid solution existed at the top and upper-middle of the Mg side interface. The second was diffusion reaction, and the two sub-layers of Al₁₂Mg₁₇ and Al₃Mg₂ formed at the lower middle and bottom of the Mg side interface. In addition, the diffusion thickness values of Al₁₂Mg₁₇ and Al₃Mg₂ layers decreased gradually from the lower middle to bottom of the Mg side interface. As the position changes from the middle to the bottom near the Mg side interface, the diffusion coefficient of Al₃Mg₂ phase rapidly decreases from 3.14 × 10⁻¹² m²/s to 6.9 × 10⁻¹³ m²/s and the diffusion coefficient of Al₁₂Mg₁₇ phase decreases from 6.8 × 10⁻¹³ m²/s to 1.5 × 10⁻¹³ m²/s. Full article