scholarly journals Mechanical Behaviour and Microstructure of Aluminum-Steel Sheets Joined by FSSW

2008 ◽  
Vol 2008 ◽  
pp. 1-8 ◽  
Author(s):  
S. Bozzi ◽  
A. L. Etter ◽  
T. Baudin ◽  
A. Robineau ◽  
J. C. Goussain
Keyword(s):  
Dwell Time ◽  
Mechanical Tests ◽  
Welding Parameters ◽  
Friction Stir ◽  
Continuous Dynamic Recrystallization ◽  
Steel Sheets ◽  
High Microhardness ◽  
Welding Spot ◽  
Continuous Dynamic ◽  
Electron Back Scattered Diffraction

At the prospect of a lightening of the automobile structures, welded spots have been realized on a stacking of two sheets (a 6008 aluminum alloy on steel) Friction Stir Spot welding (FSSW). Different process parameters have been tested, but only the influence of the dwell time will be described in the present paper. The dwell time corresponds to the time during which the probe stays in rotation at its bottom location before extracting. A study of the microstructures and textures associated to mechanical tests (tensile shear tests) allowed determining the best set of welding parameters. The recrystallized area around the welding spot has been characterized by electron back-scattered diffraction (EBSD). A mechanism of continuous dynamic recrystallization has been identified since the misorientation of subboundaries increases close to the weld, and this is for all the dwell times tested. Elsewhere, the increase of the dwell time induced a larger recrystallized zone. It has also been found that a long dwell time induced a larger welded area but also a higher quantity of intermetallic compounds (especially FeAl, Fe2Al7, and FeAl2) with high-microhardness values (up to 800 Hv). Thus, the dwell time must not exceed a certain value, otherwise it can weaken the weld.

Dynamic Recrystallization Mechanisms on Spot Welding of 6008 Aluminium Alloy to Steel by Friction Stir Welding

2007 ◽  
Vol 558-559 ◽  
pp. 477-483 ◽  
Author(s):  
Sandrine Bozzi ◽  
Anne Laure Etter ◽  
Thierry Baudin ◽  
A. Robineau ◽  
Jean Claude Goussain
Keyword(s):  
Friction Stir Welding ◽  
Dynamic Recrystallization ◽  
Aluminium Alloy ◽  
Dwell Time ◽  
Tensile Tests ◽  
Mechanical Tests ◽  
Welding Parameters ◽  
Electron Backscattered Diffraction ◽  
Friction Stir ◽  
Continuous Dynamic Recrystallization

At the prospect of a lightening of the automobile structures, welded spots have been realized on a stacking of two sheets (a 6008 aluminium alloy on steel) by Friction Stir Welding (FSW). Different process parameters have been tested but only the influence of the dwell time will be described in the present paper. The dwell time corresponds to the time during which the probe stays in rotation at its bottom location before extracting. A study of the microstructures and the crystallographic textures associated to mechanical tests (shear and tensile tests) allowed to determine the best set of welding parameters. The recrystallized area around the welding spot has been characterized by Electron BackScattered Diffraction (EBSD). The aim of the present work is to identify the recrystallization mechanisms which occur during welding, and to understand the influence of the dwell time on the recrystallized area. A mechanism of continuous dynamic recrystallization has been identified since misorientation of sub-boundary increases close to the weld and this for all the dwell times tested. Elsewhere, it has been found that the increase of the dwell time induces a larger recrystallized zone.

Microstructural Evolution of AA6082 with Small Aluminides under Hot Torsion and Friction Stir Processing

2013 ◽  
Vol 753 ◽  
pp. 263-266 ◽  
Author(s):  
Cecilia Poletti ◽  
Friedrich Krumphals ◽  
Stefan Mitsche ◽  
Zeng Gao
Keyword(s):  
Local Deformation ◽  
Large Strains ◽  
Fem Simulations ◽  
Friction Stir ◽  
Fine Grained ◽  
Continuous Dynamic Recrystallization ◽  
Hot Torsion ◽  
Continuous Dynamic ◽  
Hot Rolled

The hot rolled AA6082 aluminium alloy with aluminide dispersoids is deformed up to large strains to obtain a fine grained microstructure. Friction stir spot welding (FSSW) is carried out on rolled plates by means of a device provided by MTS System Corporation. FEM simulations determine that the material can flow up to local strains between 10 and 50 when the material reaches temperatures between 300-500°C. With this information, hot torsion tests at constant temperatures are carried out in a Gleeble ® 3800 machine for different strain rates. In both cases, in situ water quenching is applied to freeze the microstructure and avoid any static recrystallization effect after hot deformation. Light optical microscopy is used to identify the evolution of the grains as a function of the local deformation parameters determined by FEM simulations. The microstructure development by FSSW as well as by torsion is then further characterized by means of EBSD. At small strains the material deforms mainly by dynamic recovery with small low angle grain boundary formation and boundary dragging by fine aluminides and Mg2Si. At large strains grain refinement by continuous dynamic recrystallization takes place heterogeneously as a function of the original crystallographic orientation and precipitation state of each grain.

Effect of Welding Parameters on Temperature Distribution During Friction Stir Spot Welding of Commercial Pure Copper Lap Joint

2018 ◽  
Author(s):  
Ahmed Mahgoub ◽  
Abdelaziz Bazoune ◽  
Fadi Al-Badour ◽  
Necar Merah ◽  
Abdelrahman Shuaib
Keyword(s):  
Rotational Speed ◽  
Spot Welding ◽  
Dwell Time ◽  
Pure Copper ◽  
Friction Stir Spot Welding ◽  
Temperature History ◽  
Welding Parameters ◽  
Deformation Model ◽  
Friction Stir ◽  
Good Agreement

In this paper, a Coupled Eulerian Lagrangian (CEL) finite element model (FEM) was developed to simulate the friction stir spot welding (FSSW) of commercial pure copper. Through simulations results, the paper presents and discusses the effect of FSSW process parameters; namely rotational speed, plunging rate and dwell time, on the developed temperatures and their distribution within the workpiece as well as material flow and deformation. Model validation showed a good agreement between predicted temperature history and the experiment one, with a maximum error of 6%. Furthermore, the predicted formation of flash was also found in good agreement with the experiment with an error of only 7%. Simulation results predicted peak temperature and plastic strain among all studied welding conditions were 920 K and 3.5 respectively at 1200 rpm rotational speed, 20 mm/min plunging rate and 4 seconds dwell time, which is approximately 70% of the melting point of pure copper.

Effects of process parameters on the lap joint strength and morphology in friction stir spot welding of ABS sheets

2020 ◽  
pp. 009524432096152
Author(s):  
Asil Ayaz ◽  
Aydin Ülker
Keyword(s):  
Spot Welding ◽  
Dwell Time ◽  
Joint Strength ◽  
Friction Stir Spot Welding ◽  
Welding Parameters ◽  
Shear Load ◽  
Lap Joint ◽  
Friction Stir ◽  
Joint Shear ◽  
Tool Rotation

In this study, a new method was proposed to reduce the keyhole volume with friction stir spot welding process and improve the lap joint shear load-carrying capacity of the weld by analyzing the effects of tool rotation speed, plunge depth and dwell time on the weld. Single lap shear tests were carried out to determine the influences of the welding parameters on the mechanical behavior of the welds. The quality of the joint was evaluated by examining the characteristics of the joint as a result of the lap joint shear load. For friction stir spot welding of the acrylonitrile butadiene styrene samples, the experiments were designed according to Taguchi’s L9 orthogonal array in a randomized way. From the analysis of variance and the signal-to-noise ratio, the significant parameters and the optimum combination level of the parameters were obtained. It was found that using a tool rotation of 1000 rpm, plunge depth 11.5 mm and dwell time of 40 s, an improved joint strength can be obtained. The results showed that joint strength was improved by an amount of 20% as compared with the optimum welding parameters to the initial welding parameters. Macrostructure examination plays an important role to determine the joint strength and evaluate the influences of each welding parameters. So, weld morphology was investigated by morphological analysis and visual comparisons. It was also observed failure modes for fractured samples having the highest, moderate and lowest lap joint shear load.

Physical and Numerical Simulations of the Microstructure Evolution in AA6082 during Friction Stir Processing by Means of Hot Torsion and FEM

2013 ◽  
Vol 762 ◽  
pp. 590-595 ◽  
Author(s):  
Friedrich Krumphals ◽  
Zeng Gao ◽  
Hassan Zamani ◽  
Stefan Mitsche ◽  
Norbert Enzinger ◽  
...  
Keyword(s):  
Strain Rate ◽  
Microstructure Evolution ◽  
Friction Stir Processing ◽  
Local Strain ◽  
Friction Stir ◽  
Continuous Dynamic Recrystallization ◽  
Fine Grained Structure ◽  
Hot Torsion ◽  
Continuous Dynamic ◽  
Different Strains

A reproduction of the conditions occurring during friction stir processing, where a fine grained structure according to the process parameters rpm, transverse speed and pressure develops is the main focus in the present work. To physically simulate such a friction stir process, hot torsion tests at constant temperatures were carried out in a Gleeble ® 3800 machine at different strains and strain rates. The specimens were immediately water quenched after hot deformation to avoid any static recrystallization. The microstructure was investigated to characterize the grain size evolution and misorientation as a function of the local strain, strain rate and temperature. Dynamic recovery was observed followed by continuous dynamic recrystallization at large deformations. By means of DEFORMTM3D the occurring strain, strain rate and temperature distributions, which are decisive for the observed microstructure evolution, were evaluated.

Effect of Welding Conditions on Sheets’ Interface Properties in Friction Stir Spot Welding of Copper

2019 ◽  
Author(s):  
Ahmed Mahgoub ◽  
Neçar Merah ◽  
Abdelaziz Bazoune
Keyword(s):  
Surface Morphology ◽  
Rotational Speed ◽  
Spot Welding ◽  
Dwell Time ◽  
Friction Stir Spot Welding ◽  
Tensile Failure ◽  
Welding Parameters ◽  
Welding Condition ◽  
Friction Stir ◽  
Joint Fracture

Abstract Friction Stir Spot Welding (FSSW) is a solid-state joining technique widely applied to high conductive metals. In this paper, the effects of FSSW parameters, namely, rotational speed (N), plunging rate (V) and dwell time (DT) on the joint fracture mode and fractured surface morphology were investigated using scanning electron microscopy (SEM). The effect of the abovementioned welding parameters on the microhardness profile along the sheets’ interface was also investigated to gain insight into the strength of the joint and the width of the bonding ligament. Two conditions were considered for each parameter 1200 rpm and 900 rpm for N, 60 mm/min and 20 mm/min for V, 4 and 2 seconds for DT. The welding condition 1200 rpm rotational speed, 20 mm/min plunging rate and 2 seconds dwell time showed a wider bonding ligament, relatively higher elongation, higher tensile failure load, and greater microhardness on the sheets’ interface. Dimple surface morphology (DSM) with regular dimples along the stir zone was also observed at the abovementioned set of process parameters.

The Role of Tool Pin Profile and Temperature on Friction Stir Welding of High Zinc Brass

2013 ◽  
Vol 685 ◽  
pp. 264-268 ◽  
Author(s):  
Afshin Emamikhah ◽  
Alireza Abbasi ◽  
Iraj Lirabi ◽  
Amir Feghhi ◽  
Ali Atefat
Keyword(s):  
Friction Stir Welding ◽  
Close Correlation ◽  
Mechanical Tests ◽  
Welding Parameters ◽  
Friction Stir ◽  
Microhardness Distribution ◽  
High Zinc ◽  
Welding Strength ◽  
Tool Pin

In this experimental study, high zinc brass was welded by friction stir welding (FSW). A threaded cylindrical tool was used for welding the brass plates in butt configuration. Mechanical tests i.e. hardness, tensile, bending, and erichsen tests were performed for evaluating the welding strength. In addition, optical microscopy (OM) and scanning electron microscopy (SEM) were used as microstructural tests for estimating the material morphology. Furthermore, temperature as a function of time was measured during the welding. The results indicated close correlation between temperature and microhardness distribution as well as the uniformity of microstructure. Moreover, the welded sample showed acceptable mechanical strength during the applied mechanical tests due to adequate primary welding parameters and tool which led to sufficient produced temperature and material bonding.

Microstructure Evolution of Martensitic Ti-6Al-4V Alloy during Warm Deformation

2014 ◽  
Vol 783-786 ◽  
pp. 679-684 ◽  
Author(s):  
Qi Chao ◽  
Peter Hodgson ◽  
Hossein Beladi
Keyword(s):  
Microstructure Evolution ◽  
Thermomechanical Processing ◽  
Microscopy Observation ◽  
Warm Deformation ◽  
Continuous Dynamic Recrystallization ◽  
Novel Approach ◽  
Resolution Electron ◽  
Continuous Dynamic ◽  
Equiaxed Grains ◽  
Electron Back Scattered Diffraction

The microstructure evolution of martensitic Ti-6Al-4V alloy was investigated through uniaxial hot compression at 700°C and a strain rate of 10-3s-1. A combination of scanning electron microscopy observation in conjunction with high resolution electron back scattered diffraction (EBSD) was used to characterize the microstructure in detail. The development of the microstructure displayed continuous fragmentation of martensitic laths with increasing strain (i.e. continuous dynamic recrystallization), concurrently with decomposition of supersaturated martensite resulting in the formation of equiaxed grains. At a strain of 0.8, an ultrafine equiaxed grained structure with mostly high angle grain boundaries was successfully obtained. The current work proposes a novel approach to produce equiaxed ultrafine grains in a Ti-6Al-4V alloy through thermomechanical processing of a martensitic starting microstructure.

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