Dissimilar Lap Joints Research Articles

Microstructural evolution and mechanical properties of dissimilar friction stir lap welding aluminum alloy 6061-T6 to ultra low carbon steel.

Joining of steel- aluminum thin sheets has been extensively studied at the beginning of 2000 years for automotive applications, in a regard to reduce vehicle weight, reducing the emissions while improving the energy security of the country.In this context the purpose of this work is to realize and study the dissimilar lap joint between a 6061-T6 aluminum alloy and ultra low carbon steel. A recent welding technique, known as "friction stir welding" was used. Joints have been obtained using coated WC–Co tools in terms of durability, the effects of process parameters including welding speeds (50 to 400 mm/min) at a constant rotation rate (1200 tr /min) and Offset in steel plate (0.2 mm) on the microstructures and mechanical properties of the joints were investigated. The joints were evaluated by mechanical testing and metallurgical analysis. Tensile shear tests, optical microscopy, and scanning electron microscopy with energy dispersive spectroscopy (EDS) were the main techniques used. The results showed that with increasing the welding speed, the tensile strength of the joints, increased up to a maximum value. The 3.6 KN maximum value of the tensile strength achieved a traverse speed of 200 mm/min. Microstructure characterization suggested that higher joint strengths were associated with thinner, ≈ 1 µm thick intermetallic reaction layers at joint interfaces.

Dissimilar laser welding of an AA6022-AZ31 lap-joint by using Ni-interlayer: Novel beam-wobbling technique, processing parameters, and metallurgical characterization

In this article, the weldability of dissimilar lap joints between 2 mm thick sheets of AA6022 aluminum (bottom) and AZ31 magnesium alloys (upper) was studied using a fiber laser with a wobbling scanner. The effects of laser beam wobbling parameters, laser power, traveling speed, and the presence of a pure nickel interlayer (∼0.1 mm thickness) is evaluated based on the microstructures and phases produced. The experimental results revealed dissimilar joint formation is highly dependent on inter-mixing, as well as fusion zone dimensions which control Al- and Mg-rich interaction zones that vary with laser power. Sound dissimilar joints were only produced by penetrating the Mg-rich interaction zone into the aluminum alloy. Joint formation benefited from suppression of Al-Mg chemical reactions using a Ni-interlayer, providing more well-dispersed and more benign phases compared to Al-Mg intermetallics at the interface during welding. The application of laser beam wobbling on a circular path with diameter of ∼0.4 mm and frequency of 1000 Hz served to reduce cracks and enhanced materials intermixing.

Influence of Gas Metal Arc Welding Parameter on Lap Joint Properties of SS400 Carbon Steel and SUS304 Stainless Steel

SS400/SUS304 steels lap joint was applied in various industries due to flexible andbeneficial properties of these dissimilar metals joint. Therefore, an investigation for optimization ofa gas metal arc welding (GMAW) for producing the dissimilar metal lap joint should be conductedfor advancing the manufacturing industries. This research applied GMAW with various currents andspeeds to weld SS400/SUS304 lap joint and studied the relationship between the parameters andresuted joint properties. The experiment showed that an increase in the wedling current and a decreasein the welding speed affected to increase the fracture strength, the displacement of the lap joint, andthe joint hardness due to high combination of the materials at the joint interface. The uncombinedmaterials at the carbon steel/weld metal interface had the different hardness and resulted to initiatethe crack that then was propergated until the joint was broken. The weld metal showed the formationof the finer and smaller dendrite structure with increasing the welding current and decreasing thewelding speed.

Towards attaining dissimilar lap joint of CuCrZr alloy and 316L stainless steel using friction stir welding

ABSTRACTCuCrZr alloy (Cu-0.8wt-%Cr-0.1wt-%Zr) and 316L stainless steel (Fe-0.03wt-%C-16wt-%Cr-10wt-%Ni) plates were successfully friction stir lap welded resulting in significant mechanical mixing of the two matrix elements, Cu and Fe, in the stir zone. The severe mixing not only led to improved load bearing response but also leads to form Cu-rich and Fe-rich regions in the weld nugget. The formation of these phases governs the failure mechanism of the joint. Tensile properties of the weld showed promising response when compared with joints made for the similar alloy pair by other welding techniques. This suggests strong feasibility of applying FSW for joining Cu and steel for nuclear applications.

Microstructure evolution and mechanical properties of friction stir spot welded dissimilar aluminum-copper joint

Dissimilar lap joints of 1060 aluminum and T2 copper were obtained by friction stir spot welding (FSSW) at various rotational speeds. The measured process variables during welding revealed that an increasing rotational speed leads to a higher peak temperature but a lower torque and plunging force due to the greater softening degree of material. A continuous CuAl2-CuAl-Al4Cu9 laminated layer developed at the Al-Cu interface under the highest rotational speed, while the interface was characterized by the interruptedly distributed CuAl2 layer under lower rotational speeds. Intermetallic compound (IMC) formation sequence for CuAl2, CuAl and Al4Cu9 was predicted according to thermodynamic principles, which is consistent with the interfacial microstructure evolution identified by the transmission electron microscope (TEM). Besides the metallurgical bonding through the IMC layer at the Al-Cu interface, joints have a Cu hook extruded upward by the pin tool from the lower Cu sheet into the upper Al sheet, which provided additional mechanical interlocking between the sheets. Tensile properties of the joints were closely related to the thickness of the IMC layer and geometric features of the hook, higher tensile properties were found in joints owning a continuous interfacial IMC layer with a proper thickness as well as a high penetration depth of the hook into the upper Al sheet.

Investigation on lap-joint friction stir welding between AA6351 alloys and DP800 steel sheets

With continuous growth and stringent demand for weight reduction in automotive structures, the automotive industry has shown an increasing interest in dissimilar aluminium–steel welding. Dissimilar lap joint between AA6351 alloys of 2 mm thickness and DP800 advanced high-strength dual-phase steel of 1 mm thickness has been attempted and joined successfully by friction stir welding with different combinations of parameters. The experimental results of this research work clearly indicate that joining of advanced high-strength steel and aluminium in lap-joint configuration is quite feasible with friction stir welding. Microstructural characterization has been performed by X-ray diffraction (XRD) technique and scanning electron microscopy (SEM). An intermetallic compounds layer was found in the interface of steel and aluminium with thickness of less than \(7 \,\upmu \hbox {m}\) and it was identified as \(\hbox {Al}_{2}\mathrm{Fe}\) and \(\hbox {Al}_{3}\mathrm{Fe}\) by XRD method. Thermal cycle has been measured and correlated with the microstructure. Shear tensile test has been performed for determining the maximum failure load for different combinations of parameters. Finally, mechanical properties and microstructural observation are correlated with each other.

Improvement of asymmetry in a friction stir welded A3003/SUS 304 lap joint by double-pass process

ABSTRACTDouble-pass process was newly performed to a friction stir welded (FSWed) A3003 aluminium alloy/SUS304 stainless steel dissimilar lap joint in order to improve the asymmetry of the FSWed joint. A sound symmetrical joint was produced by running the tool again at the bead which ˆrstly produced by FSW. Tensile strength of specimens was improved by leaving the tool distance from 2 mm to 5 mm where both edges of the stirred zone were advancing side (AS-AS joint). Micro-tensile test revealed that most of the stirred zone in the AS-AS joint with the tool distance of 5 mm fractured at A3003 base metal.

Investigations on remote laser beam welding of dissimilar joints of austenitic chromium-nickel steel (X5CrNi18-10) and aluminum alloy (AA6082-T6) for battery housings

Owing to the enormous potential of weight saving and the consequential reduction of pollutant emissions, the use of hybrid components made of steel and aluminum alloys is increasing steadily, particularly concerning automotive lightweight construction. Especially in the automotive industry, remote laser beam welding has been established as a suitable and efficient method for joining similar material for several years. In contrast to this, thermal joining of steel and aluminum alloys involves different metallurgical and technological challenges, due to the formation of hard and brittle intermetallic phases, which decrease the strength and the formability of the dissimilar joints. In this context, the results presented show investigations on remote laser beam welding for dissimilar lap joints of the austenitic chromium–nickel steel material X5CrNi18-10 and the precipitation hardening aluminum wrought alloy AA6082-T6. For example, lightweight battery housings for electromobility are potential applications for this technology. Among other things, the influence of the energy per unit length (welding speed) and the number of welding seams on the achievable strengths are analyzed. Characterization of the dissimilar joints includes the use of tensile shear tests, metallographic analyses, hardness tests, and elemental analyses, depending on the energy per unit length.

Dissimilar spot welding of aluminium alloy and galvannealed steel by metal flow-application of friction anchor welding to aluminium alloy and Zn-coated steel

ABSTRACTLap joints of an upper Al alloy (1.0-mm-thick A5052) and lower hot dip galvanized steel (1.2-mm-thick GI steel) were welded by a novel spot welding process for dissimilar metal lap joints using a new tool with the tip made of spherical ceramics, i.e. ‘Friction Anchor Welding.’ As a result, the rotating tool was plunged only to 1.3–1.4 mm from the Al alloy surface, and accordingly, a steel projection was not formed in the Al alloy sheet. Further, the Al alloy near the rotating tool was removed. However, near this removed area, the Zn layer on the GI steel melted and was removed by friction heat, and consequently, the GI steel and the Al alloy were welded. Thus, the tensile shear strength reached about 2.6 kN/point.

Tensile and fatigue properties of single lap joints of aluminium alloy/glass fibre reinforced composites fabricated with different joining methods

The tensile and fatigue properties of single similar and dissimilar lap joints of aluminium alloy (AA7075) and glass fibre reinforced epoxy (GRE) composite were investigated. Three joining methods were employed: mechanically fastened Huck bolted joints, Araldite epoxy adhesive bonded joints and hybrid joints comprising adhesive and Huck bolts. Tensile-shear fatigue tests were performed using single lap joint specimens at the stress ratio R = 0.1 to determine the fatigue behaviour of the joints. Subsequently, S–N curves were drawn for different levels of stress amplitude (30%, 40%, 50%, 60%, 70%, 80% and 90%). The micro structures of the fractured surfaces were examined by field emission scanning electron microscopy. The experimental results show that the hybrid joints with dissimilar adherends exhibit the highest strength and stiffness, with predominantly mix-mode failure and shear-out tension of the Huck bolt. These two failure mechanisms were detected as primary and secondary failures in the hybrid joint.

Effects of processing parameters on the characteristics of dissimilar friction-stir-welded joints between AA5058 aluminum alloy and PMMA polymer

In this research, newly modified solid-state friction-stir welding (FSW) technology was employed to bond the sheets of an aluminum-magnesium alloy (AA5058) and poly-methyl-methacrylate (PMMA) in a lap-joint design. Effects of processing parameters including tool rotational speed (w), traverse velocity (v), tilt angle and plunge depth on the surface morphology, materials flow pattern, microstructural characteristics, and mechanical properties of the dissimilar FSWed joints were studied. The geometry of U-antler macro-mechanical interlocking and interfacial micro- and nano-scale chemical bonding was mainly controlled by the tool tilting angle. A sound dissimilar weld with the highest tensile strength of around 45 MPa was attained at an optimum working window containing w = 1600 rpm, v = 25 mm/min, tool tilt angle of 2°, and plunge depth of 0.2 mm. Fracture of dissimilar lap joints occurred during transverse tensile-shear testing from the weld-polymer interface with a maximum strength ratio of ~ 60% by detachment of aluminum U-antler from the solidified polymer.

Dissimilar spot welding of aluminium alloy and hot dip galvanised steel by metal flow: application of friction anchor welding to aluminium alloy and Zn-coated steel

Lap joints of an upper Al alloy (1.0 mm-thick A5052) and lower hot dip galvanized steel (1.2 mm-thick GI steel) were welded by a novel spot welding process for dissimilar metal lap joints using a new tool with the tip made of spherical ceramics, i.e. ‘Friction Anchor Welding’. As a result, the rotating tool was plunged only to 1.3–1.4 mm from the Al alloy surface, and accordingly, a steel projection was not formed in the Al alloy sheet. Further, the Al alloy near the rotating tool was removed. However, near this removed area, the Zn layer on the GI steel melted and was removed by friction heat, and consequently, the GI steel and the Al alloy were welded. Thus, the tensile shear strength reached about 2.6 kN/point.

Optimization of Laser Lap Joining between Stainless Steel 304 and Acrylonitrile Butadiene Styrene (ABS)

In principle, a laser can weld any materials, which can be joined by conventional and other nonconventional processes. Dissimilar joining technologies find applications in many sectors including microelectronics, medical and aerospace. The laser weldability of dissimilar materials depends on many factors such as physical and chemical properties. In the presented study, the laser lap joint of stainless steel 304 and acrylonitrile butadiene styrene (ABS) is investigated using a continuous wave fiber laser. All the important parameters such as laser power and welding speed based on full factorial method have been considered in this paper. The quality criteria considered to determine the optimal parameter settings were the maximization of shearing force. The collected data has been analyzed by analysis of variance (ANOVA) method to find the significance factor that effects on laser welding of stainless steel 304 and ABS. A focused beam with laser power 230W and welding speed 16mm/s were identified as the optimal set of laser welding parameters to obtain stronger and better welds. This research is conducted to reveal the possible of strong dissimilar lap joint by a direct joining laser radiation without using adhesive bonds or mechanical fasteners.

Effects of Laser Brazing Condition on Dissimilar Lap Joint Formation of Stainless Steel and Titanium

Effects of Laser Brazing Condition on Dissimilar Lap Joint Formation of Stainless Steel and Titanium

Fracture toughness and fatigue crack behaviour of A3003/SUS304 lap friction stir welded joints

Friction stir welding (FSW) can weld dissimilar metal joints without a thick and brittle intermetallic compound layer at the weld interface. In this study, the dissimilar lap joint of A3003 aluminium alloy and SUS304 stainless steel was successfully welded by FSW, and the joint obtained was tested to examine the properties of fracture toughness and fatigue crack growth rate. Its fracture toughness was different by the directions of crack propagation. The fracture toughness of advancing side (AS) to retreating side (RS) was stronger than that of RS to AS, and that of cryogenic temperature was stronger than that of room temperature. Its fatigue crack growth rate also showed the same tendency as its fracture toughness. These data were compared with the past data and discussed.

Dissimilar titanium/aluminum friction stir welding lap joints by experiments and numerical simulation

Dissimilar lap joints were produced by friction stir welding (FSW) out of Ti6Al4V titanium alloy and AA2024 aluminum alloy sheets. The joints, welded with varying tool rotation and feed rate, were studied by analyzing the maximum shear strength, Vickers microhardness and optical observations. A dedicated numerical model, able to take into account the presence of the two different alloys, was used to highlight the effects of the process parameters on temperature distribution, strain distribution, and material flow. The combined analysis of experimental measurements and numerical predictions allowed explaining the effects of tool rotation and feed rate on the material flow. It was found that tool rotation had a larger impact on the joint effectiveness with respect to feed rate. A competition between material mixing and heat input occurs with increasing tool rotation, resulting in higher joint strength when lower values of tool rotation are used.

Influence of polarity on mechanical properties of dissimilar resistance spot welds of DP 600/AISI 304 steels

The influence of polarity during resistance spot weld (RSW) of dissimilar lap joints on mechanical properties and failure mode is assessed in this work. A dissimilar lap joint was set using DP 600 dual phase steel with AISI 304 stainless steel. The experiments were performed on a medium-frequency direct current spot welding machine with proper data acquisition of voltage and welding current. Temperature evolution was also acquired by using IR camera. The mechanical properties of spot welds were evaluated by using a coach peel testing. The effect of welding current and welding time on mechanical properties was also evaluated. Correlations between polarity with the welding nugget size, failure mode, tensile strength, temperature evolution and dynamic resistance were analysed. The analysis confirmed that the polarity on dissimilar lap joints affects the behaviour of dissimilar RSWs.

Friction stir spot fusion welding of low-carbon steel to aluminum alloy

Dissimilar lap joints for a low carbon steel (SS400) sheet with thickness of 2mm on a 6061-T6 Al alloy sheet with thickness of 5mm or 10mm were created by a process called friction stir spot fusion welding (FSSFW) using an assembly-embedded rod (AER) tool under a downward force of 12kN and a rotational speed of 1200rpm at different dwell times. The Al alloy sheet was melted at the central area of the faying surface, so that two IMC layers were formed at this surface and identified as Fe2Al5 and Fe4Al13, as detected by XRD and SEM images. The IMC thickness increased along with dwell time, but its increment rate became slower for IMC thickness larger than 25μm. The failure load increased along with the IMC thickness, but the failure load decreased quickly for IMC thickness larger than 17μm. It was able to achieve 18–22kN for the thickness of the IMC layer in the range of 6–17μm for a dwell time from 35–55s. The larger the crack was, the smaller the failure load.

Microstructure and tensile properties of dissimilar submerged friction stir welds between HDPE and ABS sheets

In this paper, dissimilar lap joints of high-density polyethylene (HDPE) and acrylonitrile butadiene styrene (ABS) sheets were obtained by submerged friction stir welding. The multiwalled carbon nanotubes (MWCNTs) were introduced into the HDPE/ABS joint in order to improve the tensile properties of the joints. The effects of different rotational rates, plunge depths, and traverse speeds on the microstructure and tensile strength of joints were investigated. Microstructural evolution of joints fabricated at different process parameters had been observed using a field emission scanning electron microscope (FESEM). Some defects such as pores and cracks were found at inappropriate processing parameters. The tensile test was carried out as the mechanical properties of joints. The maximal tensile strength was 14.7 MPa, which reached more than 65.3 % of the parent HDPE strength.

Microstructures and mechanical properties of friction stir welded brass/steel dissimilar lap joints at various welding speeds

The dissimilar lap joints of commercially brass (Cu–40Zn) to plain carbon steel (S25C) were fabricated using friction stir welding. The relationship between welding speed and heat input during the friction stir welding processes was discussed. The effect of welding speed on microstructures and mechanical properties of brass/S25C dissimilar joints was investigated. The grain size, Vickers hardness at the stirred zone and tensile shear fracture load of the joints varied significantly with the change of welding speed. The transmission electron microscope observations and energy dispersive X-ray spectrometry line analyses at the interface revealed that a mutual diffusion zone of Cu, Zn and Fe, the dominant elements of each plate was formed at the interface. The microstructure evolution and the joining mechanism of the brass/S25C joint are systematically discussed.