scholarly journals Microstructure and mechanical properties of an ultrasonic spot welded aluminum alloy: the effect of welding energy

2021 ◽  
Author(s):  
He Peng ◽  
Daolun Chen ◽  
Xianquan Jiang
Keyword(s):  
Shear Strength ◽  
Aluminum Alloy ◽  
Cyclic Loading ◽  
Crack Growth ◽  
Failure Mode ◽  
Spot Welding ◽  
Energy Levels ◽  
Lap Shear Strength ◽  
Pull Out ◽  
Lap Shear

The aim of this study is to evaluate the microstructures, tensile lap shear strength, and fatigue resistance of 6022-T43 aluminum alloy joints welded via a solid-state welding technique–ultrasonic spot welding (USW)–at different energy levels. An ultra-fine necklace-like equiaxed grain structure is observed along the weld line due to the occurrence of dynamic crystallization, with smaller grain sizes at lower levels of welding energy. The tensile lap shear strength, failure energy, and critical stress intensity of the welded joints first increase, reach their maximum values, and then decrease with increasing welding energy. The tensile lap shear failure mode changes from interfacial fracture at lower energy levels, to nugget pull-out at intermediate optimal energy levels, and to transverse through-thickness (TTT) crack growth at higher energy levels. The fatigue life is longer for the joints welded at an energy of 1400 J than 2000 J at higher cyclic loading levels. The fatigue failure mode changes from nugget pull-out to TTT crack growth with decreasing cyclic loading for the joints welded at 1400 J, while TTT crack growth mode remains at all cyclic loading levels for the joints welded at 2000 J. Fatigue crack basically initiates from the nugget edge, and propagates with “river-flow” patterns and characteristic fatigue striations. Keywords: aluminum alloy; ultrasonic spot welding; EBSD; microstructure; tensile strength; fatigue

scholarly journals Microstructure and mechanical properties of an ultrasonic spot welded aluminum alloy: the effect of welding energy

2021 ◽  
Author(s):  
He Peng ◽  
Daolun Chen ◽  
Xianquan Jiang
Keyword(s):  
Shear Strength ◽  
Aluminum Alloy ◽  
Cyclic Loading ◽  
Crack Growth ◽  
Failure Mode ◽  
Spot Welding ◽  
Energy Levels ◽  
Lap Shear Strength ◽  
Pull Out ◽  
Lap Shear

The aim of this study is to evaluate the microstructures, tensile lap shear strength, and fatigue resistance of 6022-T43 aluminum alloy joints welded via a solid-state welding technique–ultrasonic spot welding (USW)–at different energy levels. An ultra-fine necklace-like equiaxed grain structure is observed along the weld line due to the occurrence of dynamic crystallization, with smaller grain sizes at lower levels of welding energy. The tensile lap shear strength, failure energy, and critical stress intensity of the welded joints first increase, reach their maximum values, and then decrease with increasing welding energy. The tensile lap shear failure mode changes from interfacial fracture at lower energy levels, to nugget pull-out at intermediate optimal energy levels, and to transverse through-thickness (TTT) crack growth at higher energy levels. The fatigue life is longer for the joints welded at an energy of 1400 J than 2000 J at higher cyclic loading levels. The fatigue failure mode changes from nugget pull-out to TTT crack growth with decreasing cyclic loading for the joints welded at 1400 J, while TTT crack growth mode remains at all cyclic loading levels for the joints welded at 2000 J. Fatigue crack basically initiates from the nugget edge, and propagates with “river-flow” patterns and characteristic fatigue striations. Keywords: aluminum alloy; ultrasonic spot welding; EBSD; microstructure; tensile strength; fatigue

scholarly journals Ultrasonic spot welding of lightweight alloys

2021 ◽  
Author(s):  
Vikas Patel
Keyword(s):  
Shear Strength ◽  
Spot Welding ◽  
Intermetallic Layer ◽  
Zinc Coating ◽  
Micro Hardness ◽  
Simultaneous Application ◽  
Lap Shear Strength ◽  
Lap Shear ◽  
Structural Applications ◽  
Welding Processes

Automotive and aerospace sectors have a pressing need for structural components that are lighter and stronger, aiming to improve energy efficiencies and reduce anthropogenic environment. Steel has already a wide variety of structural applications in the transportation industry due to its excellent properties. To further reduce CO2 emissions, lightweight magnesium (Mg) and aluminum (Al) alloys have increasingly been used in the vehicle fabrication due to their lower density, higher specific strength and stiffness, excellent size stability and process ability. The structural application of these alloys inevitably involves welding and joining of similar Mg-to-Mg and Al-to-Al, and dissimilar Mg-to-Al, Mg-to-steel and Al-to-steel. Resistance spot welding produces coarse grains, large defects and thick brittle intermetallic compounds (IMCs) in the weld metal. Alternative solid-state welding processes are being considered such as ultrasonic spot welding (USW), which produces coalescence through the simultaneous application of localized high-frequency vibratory energy and moderate clamping forces. In this study, USW was successfully carried out on similar Mg alloy and dissimilar Mg-to-Al, Mg-to-steel and Al-to-steel alloys. The overall objective of this work is to gain a better understanding of the dominant factors determining the joint performance, with particular emphasis on the microstructural evolution, crystallographic texture, micro-hardness, lap shear strength, fatigue resistance, fatigue life prediction model and fracture analysis of similar and dissimilar USWed joints. Overall, USWed Mg-to-Mg is stronger and more consistent in terms of weldability than the dissimilar USWed Mg-to-Al, Mg-to-steel and Al-to-steel. This was attributed to the large volume of thick brittle IMCs and significantly higher welds center hardness in dissimilar metals welding, which is the main cause of joint failure. The IMCs were confirmed by XRD, EDS and micro-hardness measurement tests.. Therefore, another objective of this study is to minimize the presence of brittle IMCs and engineer an acceptable intermetallic layer to produce sound joints between Mg-to-Al, Mg-to-steel and Al-to-steel. A third material (tin foil or zinc coating) was placed in-between the work pieces. With this procedure, the lap shear strength of the welded samples was increased. The detailed microstructural characterization and mechanical properties of welded joints with an interlayer are presented.

scholarly journals Parameters optimization for friction spot welding of AZ31 magnesium alloy by Taguchi method

2012 ◽  
Vol 17 (1) ◽  
pp. 26-31 ◽  
Author(s):  
Leonardo Contri Campanelli ◽  
Uceu Fuad Hasan Suhuddin ◽  
Jorge Fernandez dos Santos ◽  
Nelson Guedes de Alcântara
Keyword(s):  
Shear Strength ◽  
Magnesium Alloy ◽  
Rotational Speed ◽  
Spot Welding ◽  
Dwell Time ◽  
Az31 Magnesium Alloy ◽  
Lap Shear Strength ◽  
Plunge Depth ◽  
Friction Spot Welding ◽  
Lap Shear

Friction spot welding (FSpW) is a solid state welding process suitable for producing spot-like joints, especially in lightweight materials, which are particularly interesting due to the weight saving potential. The plunging of an especially designed non-consumable and rotating tool creates a connection between overlapped sheets through frictional heat and plastic deformation. Minimum material loss is observed, and therefore a fully consolidated joint with flat surface (no keyhole) is obtained. In the current study, the effect of FSpW parameters, such as rotational speed, plunge depth and dwell time, on lap shear strength of AZ31 magnesium alloy joints was investigated. The optimization of input process parameters was carried out through Taguchi approach of DOE. Analysis of variance was applied to determine the individual importance of each parameter. Main effect plots were used to indicate the best levels for maximizing lap shear strength. The results show that tool plunge depth has the higher effect on the weld strength, followed by rotational speed and dwell time.

scholarly journals Ultrasonic spot welding of lightweight alloys

2021 ◽  
Author(s):  
Vikas Patel
Keyword(s):  
Shear Strength ◽  
Spot Welding ◽  
Intermetallic Layer ◽  
Zinc Coating ◽  
Micro Hardness ◽  
Simultaneous Application ◽  
Lap Shear Strength ◽  
Lap Shear ◽  
Structural Applications ◽  
Welding Processes

Automotive and aerospace sectors have a pressing need for structural components that are lighter and stronger, aiming to improve energy efficiencies and reduce anthropogenic environment. Steel has already a wide variety of structural applications in the transportation industry due to its excellent properties. To further reduce CO2 emissions, lightweight magnesium (Mg) and aluminum (Al) alloys have increasingly been used in the vehicle fabrication due to their lower density, higher specific strength and stiffness, excellent size stability and process ability. The structural application of these alloys inevitably involves welding and joining of similar Mg-to-Mg and Al-to-Al, and dissimilar Mg-to-Al, Mg-to-steel and Al-to-steel. Resistance spot welding produces coarse grains, large defects and thick brittle intermetallic compounds (IMCs) in the weld metal. Alternative solid-state welding processes are being considered such as ultrasonic spot welding (USW), which produces coalescence through the simultaneous application of localized high-frequency vibratory energy and moderate clamping forces. In this study, USW was successfully carried out on similar Mg alloy and dissimilar Mg-to-Al, Mg-to-steel and Al-to-steel alloys. The overall objective of this work is to gain a better understanding of the dominant factors determining the joint performance, with particular emphasis on the microstructural evolution, crystallographic texture, micro-hardness, lap shear strength, fatigue resistance, fatigue life prediction model and fracture analysis of similar and dissimilar USWed joints. Overall, USWed Mg-to-Mg is stronger and more consistent in terms of weldability than the dissimilar USWed Mg-to-Al, Mg-to-steel and Al-to-steel. This was attributed to the large volume of thick brittle IMCs and significantly higher welds center hardness in dissimilar metals welding, which is the main cause of joint failure. The IMCs were confirmed by XRD, EDS and micro-hardness measurement tests.. Therefore, another objective of this study is to minimize the presence of brittle IMCs and engineer an acceptable intermetallic layer to produce sound joints between Mg-to-Al, Mg-to-steel and Al-to-steel. A third material (tin foil or zinc coating) was placed in-between the work pieces. With this procedure, the lap shear strength of the welded samples was increased. The detailed microstructural characterization and mechanical properties of welded joints with an interlayer are presented.

scholarly journals Failure Study of Two Dissimilar Steels Joined by Spot Welding Technique

2018 ◽  
Vol 778 ◽  
pp. 262-267
Author(s):  
Ali Dad Chandio ◽  
Nabeel Ahmed Khan ◽  
Rameez Jawaid ◽  
Syed Naqi Mohsin
Keyword(s):  
Failure Mode ◽  
Fusion Zone ◽  
Resistance Spot Welding ◽  
Spot Welding ◽  
Sheet Material ◽  
Weld Zone ◽  
Resistance Spot ◽  
Pull Out ◽  
Lap Shear ◽  
Dissimilar Alloys

Resistance spot welding (RSW) process is of paramount importance in automotive industry for the fabrication of metallic components. Several dissimilar alloys could easily be joined by resistance spot welding. However, the joining of the stainless steel and galvanized carbon steel is challenging task since weld fusion zone properties are affected significantly. Indeed, the reliability of the component lies in the sound quality of spot weld. The overload failure mode of the weld zone was determined by preparing lap-shear specimens and then carrying out tensile-shear test. Microstructures and hardness of the weld nuggets were also brought under considerations. It was found that weld nugget size and strength of that sheet material which has lower electrical resistance are the controlling factors of the failure mode. The aim of this study was to find out the causes of spot welds failure in terms of parameters favoring the pull-out failure mode, role of fusion zone size (FZS), nugget and base metal by controlling the process parameters.

scholarly journals Simultaneous Effect of Tool Rotation and Dwell Time on Quality of Dissimilar AA5052-Copper Joints Fabricated by Friction Stir Spot Welding

2021 ◽  
Author(s):  
Aydin Jadidi ◽  
Reza Bagherian Azhiri ◽  
Amir Baghdadchi ◽  
Abolfazl Salmani Bideskan
Keyword(s):  
Shear Strength ◽  
Spot Welding ◽  
Dwell Time ◽  
Quality Characteristics ◽  
Friction Stir Spot Welding ◽  
Lap Joints ◽  
Lap Shear Strength ◽  
Friction Stir ◽  
Lap Shear ◽  
Rotary Speed

Abstract In the present study, lap joints of dissimilar 5052 aluminum alloy and pure copper were fabricated by friction stir spot welding process. The work was aimed to find effect of parameters such as tool rotary speed (1000, 1400 and 2000 RPM) and dwell time (5, 10 and 15s) on microstructure and strength properties of lap joints. Also, statistical models of the quality characteristics were developed to understand which interaction has dominant effect on quality characteristics. Research findings showed that to obtain sound joints with high lap shear strength tool rotary speed of 2000 rpm and dwell time of 5s should be selected. It provides sufficient heat input and prevents the excessive material softening. On the other hand, to achieve maximum hardness, 2000 rpm tool rotary speed should be chosen to provide enough heat for formation of intermetallic compound and 10s dwell time should be used prevent enough time for microstructure refining. Moreover, from the statistical analyses, it was found that dwell time and tool speed are the significant factor for lap shear strength and hardness, respectively. In order to attain simultaneous maximum strength and hardness, tool speed of 2000 rpm and dwell time of 8 s should be used. In such condition lap shear strength of 1755 N and hardness of 77 V are achieved with desirability of 85%.

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