Effects of Post Weld Heat Treatments (PWHT) on Friction Stir Welded AA2219-T87 Joints

2017 ◽  
Author(s):  
Mohammad W. Dewan ◽  
Muhammad A. Wahab ◽  
Khurshida Sharmin
Keyword(s):  
Mechanical Properties ◽  
Aluminum Alloys ◽  
Yield Strength ◽  
Solution Treatment ◽  
Welding Process ◽  
Alloying Elements ◽  
Age Hardening ◽  
Experimental Program ◽  
Friction Stir ◽  
Aging Period

Friction Stir Welding (FSW) offers significantly better performance on aluminum alloy joints compared to the conventional fusion arc welding techniques; however, plastic deformation, visco-plastic flow of metals, and complex non-uniform heating cycles during FSW processes, result in dissolution of alloying elements, intrinsic microstructural changes, and post-weld residual stress development. As a consequence, about 30% reduction in ultimate strength (UTS) and 60% reduction in yield strength (YS) were observed in defect-free, as-welded AA2219-T87 joints. PWHT is a common practice to refine grain-coarsened microstructures which removes or redistributes post-weld residual stresses; and improves mechanical properties of heat-treatable welded aluminum alloys by precipitation hardening. An extensive experimental program was undertaken on PWHT of FS-welded AA2219-T87 to obtain optimum PWHT conditions and improvement of the tensile properties. Artificial age-hardening (AH) helped in the precipitation of supersaturated alloying elements produced around weld nugget area during the welding process. As a result, an average 20% improvement in YS and 5% improvements in UTS was observed in age-hardened (AH-170°C-18h) specimens as compared to AW specimens. To achieve full benefit of PWHT, solution-treatment followed by age-hardening (STAH) was performed on FS-welded AA2219-T87 specimens. Solution-treatment (ST) helps in the grain refinement and formation of supersaturated precipitates in aluminum alloys. Age-hardening of ST specimens help in the precipitation of alloying elements around grain boundaries and strengthen the specimens. Optimum aging period is important to achieve better mechanical properties. For FS-welded AA2219-T87 peak aging time was 5 hours at 170°C. STAH-170°C -5h treated specimens showed about 78% JE based on UTS, 61% JE based on yield strength, and 36% JE based on tensile toughness values of base metal.

scholarly journals Effect of Artificial Aging Temperature on Mechanical Properties of 6061 Aluminum Alloy

2019 ◽  
Vol 38 (1) ◽  
pp. 31-36
Author(s):  
Mukesh Kumar ◽  
Muhammad Moazam Baloch ◽  
Muhammad Ishaque Abro ◽  
Sikandar Ali Memon ◽  
Ali Dad Chandio
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Tensile Strength ◽  
Aluminum Alloy ◽  
Aluminum Alloys ◽  
Solution Treatment ◽  
Alloying Elements ◽  
Age Hardening ◽  
6061 Aluminum Alloy ◽  
6Xxx Series

Aluminum alloys have been attracted by several engineering sectors due to their excellent strengthweight ratio and corrosion resistant properties. These are categorized into 1, 2, 3, 4, 5, 6, 7and 8xxx on the basis of alloying elements. Among these 6xxx series contains aluminum–magnesium–silicon as alloying elements and are widely used in extruded products and automotive body panels. The major advantages of these alloys are good corrosion resistance, medium strength, low cost, age hardening response no yield point phenomenon and Ludering. 6xxx series alloys generally have lower formability than other aluminum alloys which restrict their utilization for wide applications. Keeping in view of the shortcomings in the set of mechanical properties of 6xxx series the efforts were made to improve the tensile strength and toughness properties through age hardening. In present study heat treatment cycles were studied for 6061 aluminum alloy. Three different age hardening temperatures 160, 200 and 240oC were selected. The obtained results showed that 17.26, 7.69, and 10.51% improvement in tensile strength, toughness and hardness respectively was achieved with solution treatment at 380oC followed by an aging 240oC. Microstructural study revealed that substantial improvements in the mechanical properties of 6061 aluminum alloy under heat treatment were achieved due to precipitation of Mg2Si secondary phase.

Prediction and optimization of the mechanical properties of dissimilar friction stir welding of aluminum alloys using design of experiments

2016 ◽  
Vol 232 (8) ◽  
pp. 1384-1394 ◽  
Author(s):  
R Palanivel ◽  
RF Laubscher ◽  
S Vigneshwaran ◽  
I Dinaharan
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Friction Stir Welding ◽  
Aluminum Alloys ◽  
Ultimate Tensile Strength ◽  
Design Of Experiments ◽  
Process Parameters ◽  
Welding Process ◽  
Friction Stir ◽  
Friction Stir Welding Process

Friction stir welding is a solid-state welding technique for joining metals such as aluminum alloys quickly and reliably. This article presents a design of experiments approach (central composite face–centered factorial design) for predicting and optimizing the process parameters of dissimilar friction stir welded AA6351–AA5083. Three weld parameters that influence weld quality were considered, namely, tool shoulder profile (flat grooved, partial impeller and full impeller), rotational speed and welding speed. Experimental results detailing the variation of the ultimate tensile strength as a function of the friction stir welding process parameters are presented and analyzed. An empirical model that relates the friction stir welding process parameters and the ultimate tensile strength was obtained by utilizing a design of experiments technique. The models developed were validated by an analysis of variance. In general, the full impeller shoulder profile displayed the best mechanical properties when compared to the other profiles. Electron backscatter diffraction maps were used to correlate the metallurgical properties of the dissimilar joints with the joint mechanical properties as obtained experimentally and subsequently modeled. The optimal friction stir welding process parameters, to maximize ultimate tensile strength, are identified and reported.

Evolution of Mechanical Properties and Microstructural Characterization of Aluminum AA-6061 Butt-Welded Joints

2011 ◽  
Author(s):  
Ajay A. Kardak ◽  
M. A. Wahab
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Aluminum Alloys ◽  
Fracture Surface ◽  
Welded Joints ◽  
Welding Process ◽  
Post Weld Heat Treatment ◽  
Age Hardening ◽  
Welding Processes ◽  
Weld Heat

Aluminum alloys because of their high strength to weight ratio have various applications as structural material in railways, ship building, aeronautics, construction, and consumer appliances. This increased use of aluminum alloys calls for more efficient and reliable welding processes which has always represented a great challenge for designers and technologists. AA-6061 Aluminum Alloy (Al-Mg-Si) is widely used in the aircraft industry and has gathered wider acceptance in the fabrication of light weight structures. The preferred welding process for this alloy is Tungsten Inert Gas (TIG) process due to their comparatively easier applicability, high yield, and better economy. Major difficulties are associated with this type of welding process, such as, the presence of tenacious oxide layer, high coefficient of thermal expansion, solidification shrinkage, solubility of hydrogen, and other gases in the molten state. Furthermore, problems such as decay of mechanical properties due to phase transformation and softening can occur in the heat-affected-zone (HAZ). Post weld heat treatment can be used to improve the strength of the HAZ for heat-treatable alloys like AA-6061. Hence, the major objectives of this work was to conduct a systematic study and gain an in-depth understanding of the effect of post-weld heat treatment (PWHT) of these joints on tensile properties, micro hardness, microstructure, and fracture surface morphology of butt-welded joints. It was found that of all the PWHT processes, Age-hardening (AH) resulted in superior mechanical properties and hardness. The reason for this enhanced strength has also been studied from metallurgical point of view. Microstructure and fracture surface of the tensile tested specimens were studied using light microscope and scanning electron microscope, respectively. Correlation has been drawn between the tensile test results, microhardness and the metallurgical results. It was found that the uniformly dense precipitation of fine Mg2Si, and the lack of precipitate-free zone could be the reason for the superior results found.

scholarly journals Repair Welding of the Tunnel Defect in Friction Stir Weld

2018 ◽  
Vol 37 (7) ◽  
pp. 675-681 ◽  
Author(s):  
Weipo Li ◽  
Zhimin Liang ◽  
Congwei Cai ◽  
Dianlong Wang
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Yield Strength ◽  
Weld Zone ◽  
Welding Process ◽  
Friction Stir Weld ◽  
Strength Increase ◽  
Repair Welding ◽  
Friction Stir ◽  
Longitudinal Residual Stress

AbstractThe tunnel defect formed in friction stir weld would dramatically push the mechanical properties of joints into deterioration. In this study, friction stir welding process was adopted to repair the joints of 7N01 aluminum alloy with tunnel defect. The effects of friction stir repair welding process on the microstructure and mechanical properties were comprehensively investigated. Microstructure of the repaired joints shows that the grain size in nugget zone decreases slightly while the recrystallization in the retreating side of thermo-mechanically affected zone is intensified as the joints are repaired. The microhardness of the repaired joints declined slightly compared with the defective joint. However, the yield strength and tensile strength increase and recover to the values of the joints free of defect. The longitudinal residual stress in weld zone increased remarkably as the repair times increase. Compared with the once repaired joint, yield strength and tensile strength of the twice repaired joint reduced slightly, and the throat thickness also reduced during the repeated repair welding process. Therefore, the times of repair welding applied should be limited actually.

scholarly journals Friction-Stir Welding of a Wrought Al-Si-Mg Alloy in As-Fabricated and Heat-Treatment States

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 861
Author(s):  
Chunxia Wang ◽  
Hongbo Cui ◽  
Xin Tang ◽  
Kezhun He
Keyword(s):  
Heat Treatment ◽  
Friction Stir Welding ◽  
Solution Treatment ◽  
Base Material ◽  
Welding Process ◽  
Age Hardening ◽  
Weld Strength ◽  
Friction Stir ◽  
Joint Efficiency ◽  
Al Matrix

A wrought Al-11.3Si-0.6Mg alloy under hot extrusion (T1), solution treatment (T4), and solution treatment + artificial aging (T6) states were friction stir welded at welding speed of 100 mm/min and rotation rate of 800 rpm. The effect of prior heat-treatment on the microstructure and mechanical properties of the welds were investigated. The results show that the microstructures of the nugget zones have little dependence on the initial states of the base material. In the nugget zones, complete recrystallized structures with equaxied grains in the Al matrix were formed under all conditions. The Si particles in the nugget zones are almost unchanged compared with those of their base materials (BMs) in the three states. In contrast, the joint efficiency of the obtained welds was very sensitive to the initial material condition. The joint efficiency under the T1 state is more than 90% due to the fact that the microstructure is almost unchanged, except for the slight coarsening of the Al matrix grains and some of the Mg2Si phases during the friction stir welding process. However, the joint efficiency in the T4 and T6 conditions is only 77.22% and 62.03%, respectively. The relatively low weld strength in the T4 and T6 conditions is due to the elimination of the solid solution strengthening and age hardening effects during friction stir welding. The hardness distributions along the cross section of joints are all W-shaped under T1, T4, and T6 conditions.

scholarly journals Mechanical Properties Of Butt Welded AZ31B Magnesium Alloys

2021 ◽  
Author(s):  
MD. S.M. Chowdhury
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Fatigue Strength ◽  
Ultimate Tensile Strength ◽  
Yield Strength ◽  
Welding Process ◽  
Fusion Welding ◽  
Friction Stir ◽  
Brittle Phase ◽  
Welding Defect

Mechanical properties of friction stir welded (FSWed), double sided arc welded (DSAWed), fiber laser welded (FLWed) and diode laser welded (DLWed) on AZ31B Mg alloy were studied. After welding, grains at the centre became recrystallized. Brittle phase β-Mg₁₇AI₁₂ particles observed at the centre of the joint during fusion welding process. The yield strength (YS), ultimate tensile strength (UTS) and fatigue strength were lower in the FDWed samples than in the DSAWed samples. Welding defect at the bottom of the FDWed joint was observed when right hand thread (RHT) weld tool was considered. In FLWed joint, YS, UTS and fatigue strength, with a joint efficiency of ~91% was achieved while the YS, UTS and fatigue strength of the DLWed joints were notably lower. The DSAWed joints and DLWed joints exhibited a higher strain hardening capacity in comparison with the FSWed joints and FLWed joints, respectively.

scholarly journals Effects of Refill Friction Stir Spot Weld Spacing and Edge Margin on Mechanical Properties of Multi-Spot-Welded Panels

2020 ◽  
Vol 4 (2) ◽  
pp. 55
Author(s):  
Guruvignesh Lakshmi Balasubramaniam ◽  
Enkhsaikhan Boldsaikhan ◽  
Shintaro Fukada ◽  
Mitsuo Fujimoto ◽  
Kenichi Kamimuki
Keyword(s):  
Mechanical Properties ◽  
Aluminum Alloys ◽  
Spot Welding ◽  
Welding Process ◽  
Spot Weld ◽  
Plastic Deformations ◽  
Friction Stir ◽  
Experimental Strategy ◽  
Failure Loads ◽  
Spot Welded

Refill friction stir spot welding (RFSSW) is an emerging technology for joining aerospace aluminum alloys. The aim of the study is to investigate the effects of the refill friction stir spot weld spacing and the edge margin on the mechanical properties of multi-spot-welded AA7075-T6 panels. AA7075-T6 is a baseline aerospace aluminum alloy used in aircraft structures. The study employs an innovative robotic RFSSW system that is designed and developed by Kawasaki Heavy Industries (KHI). The experimental strategy uses Design of Experiments (DoE) to characterize the failure loads of multi-spot-welded panels in terms of the spot weld spacing, edge margin, and heat-affected zone (HAZ) of the spot weld. The RFSSW process leaves behind a thermal “imprint” as HAZ in heat-treatable aluminum alloys. According to the DoE results, larger spot weld spacings with no HAZ overlap produce higher failure loads of multi-spot-welded panels. On the other hand, edge margins that are equal to or less than the spot weld diameter demonstrate abnormal plastic deformations, such as workpiece edge swelling and weld crown dents, during the RFSSW process. The larger edge margins do not demonstrate such abnormal deformations during the welding process.

A Survey of the Parameters of the Friction Stir Welding Process of Aluminum Alloys 6xxx Series

2021 ◽  
Vol 9 (1) ◽  
pp. 51-60
Author(s):  
Meshal Essa ◽  
Fahad Salem Alhajri
Keyword(s):  
Mechanical Properties ◽  
Friction Stir Welding ◽  
Aluminum Alloys ◽  
Welding Process ◽  
Literature Survey ◽  
Friction Stir ◽  
Friction Stir Welding Process ◽  
Welding Processes ◽  
6Xxx Series

Friction stir welding is a modern innovation in the welding processes technology, there are ‎several ways in which this technology has to be investigated in order to refine and make it ‎economically responsible. Aluminum alloys have strong mechanical properties when they are ‎welded by using the Friction Stir welding. Therefore, certain parameters of the welding ‎process need to be examined to achieve the required mechanical properties. In this project, a ‎literature survey has been performed about the friction stir welding process and its parameters ‎for 6xxx series aluminum alloys‎.  

scholarly journals Mechanical Properties Of Butt Welded AZ31B Magnesium Alloys

2021 ◽  
Author(s):  
MD. S.M. Chowdhury
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Fatigue Strength ◽  
Ultimate Tensile Strength ◽  
Yield Strength ◽  
Welding Process ◽  
Fusion Welding ◽  
Friction Stir ◽  
Brittle Phase ◽  
Welding Defect

Mechanical properties of friction stir welded (FSWed), double sided arc welded (DSAWed), fiber laser welded (FLWed) and diode laser welded (DLWed) on AZ31B Mg alloy were studied. After welding, grains at the centre became recrystallized. Brittle phase β-Mg₁₇AI₁₂ particles observed at the centre of the joint during fusion welding process. The yield strength (YS), ultimate tensile strength (UTS) and fatigue strength were lower in the FDWed samples than in the DSAWed samples. Welding defect at the bottom of the FDWed joint was observed when right hand thread (RHT) weld tool was considered. In FLWed joint, YS, UTS and fatigue strength, with a joint efficiency of ~91% was achieved while the YS, UTS and fatigue strength of the DLWed joints were notably lower. The DSAWed joints and DLWed joints exhibited a higher strain hardening capacity in comparison with the FSWed joints and FLWed joints, respectively.

Modeling of Friction Stir Welding of AL7075 Using Neural Networks

2012 ◽  
Vol 3 (1) ◽  
pp. 66-79 ◽  
Author(s):  
Sasidhar Muttineni ◽  
Pandu R. Vundavilli
Keyword(s):  
Neural Network ◽  
Mechanical Properties ◽  
Neural Networks ◽  
Friction Stir Welding ◽  
Aluminum Alloys ◽  
High Speed ◽  
Welding Process ◽  
High Speed Steel ◽  
Operating Conditions ◽  
Friction Stir

Friction stir welding (FSW) is a solid state welding process, which is used for the welding of aluminum alloys. It is important to note that the mechanical properties of the FSW process depends on various process parameters, such as spindle speed, feed rate and shoulder depth. Two different tool materials, such as High speed steel (HSS) and H13 are considered for the welding of Al 7075. The present paper deals with the modeling of FSW process using neural networks. A three layered feed forward neural network (NN) has been used to model the FSW of aluminum alloys. It is important to note that the connection weights and bias values of the NN are optimized with the help of a binary coded genetic algorithm (GA). The training of the NN with the help of GA is a time consuming process. Hence, offline training has been provided to optimize the connection weights and bias values of the neural network. Once, the training is over, the GA trained neural network will be used for online prediction of the mechanical properties of FSW process at different operating conditions.

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