Improvement in Fatigue Strength of Friction Stir Welded Aluminum Alloy Plates by Laser Peening

2014 ◽  
Vol 891-892 ◽  
pp. 969-973 ◽  
Author(s):  
Yuji Sano ◽  
Kiyotaka Masaki ◽  
Keiichi Hirota
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Strength ◽  
Fatigue Testing ◽  
Large Deviation ◽  
Fatigue Cracks ◽  
Weld Zone ◽  
Base Material ◽  
Fatigue Properties ◽  
Laser Peening ◽  
Friction Stir

Plane bending fatigue testing was performed to study the fatigue properties of friction stir welded (FSW) 3 mm thick AA6061-T6 aluminum alloy plates. Fatigue cracks propagated with bends and curves on the specimens, showing large deviation from a linear line. This might be reflecting the material flow and microstructure in the weld zone. The fatigue strength of the unwelded base material (BM) was 110 MPa at 107 cycles and FSW deteriorated it to 90 MPa. However, laser peening (LP) restored the degraded fatigue strength up to 120 MPa which is higher than that of the BM.

S–N curves for fatigue life estimation of friction stir welded 19501 aluminum alloy T-joint

2018 ◽  
Vol 233 (2) ◽  
pp. 664-674
Author(s):  
Prakash Chandra Gope ◽  
Harshit Kumar ◽  
Himanshu Purohit ◽  
Manish Dayal
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Life ◽  
Fatigue Strength ◽  
Weld Zone ◽  
Stress Effect ◽  
Mean Stress ◽  
Friction Stir ◽  
Fracture Surfaces ◽  
Mean Stress Effect ◽  
Metallic Bonding

In this study, the mechanical properties and fatigue life of 19501 aluminum alloy friction stir welded T-joint is investigated. Tensile properties of friction stir welded joint show that there is a marginal reduction of about 5% in strength and ductility as compared to unwelded 19501 aluminum alloy. Fatigue test results of T-joint specimen at two stress ratios of 0 and -1 show that there is a reduction of 15% in fatigue strength due to change of stress ratio from -1 to 0. Also, higher variation is seen in fatigue strength in low cycle zone than the high cycle zone. Effect of mean stress on fatigue life is discussed on the basis of different mean stress effect models. Morrow’s mean stress effect model is found to be better than other models. Micrographs from the fracture surfaces of retreating side, mid weld zone, and advancing side of the T-joint indicates that fracture surfaces are cleavage fracture. Different sizes of inter-metallic bonding are seen in the micrographs, which indicate that fracture is initiated due to breaking of the brittle inter-metallic bonding.

Nonuniformity of Mechanical Property in the Weld Zone of Friction Stir Welded 7050 Aluminum Alloy Joint

2011 ◽  
Vol 189-193 ◽  
pp. 3560-3563
Author(s):  
Yu Wen Tian ◽  
Fei Xu ◽  
Wen Ya Li ◽  
Zhong Bin Tang
Keyword(s):  
Mechanical Property ◽  
Aluminum Alloy ◽  
Elastic Modulus ◽  
Weld Zone ◽  
Base Material ◽  
Weld Nugget ◽  
Second Phase ◽  
Nugget Zone ◽  
Friction Stir ◽  
7050 Aluminum Alloy

The distribution of mechanical property in the weld zone of friction stir welded 7050 aluminum alloy joint along the plane perpendicular to the welding direction was experimentally investigated by the non-contact measurement method. The results show that the elastic modulus presents a W-shape distribution across the weld zone. The elastic modulus in the weld nugget zone is increased due to the grain refinement. In addition, the elastic modulus in the advancing side is slightly less than that in the retreating side possibly because of the relatively higher temperature in the advancing side during the welding process. The strength in the vicinity of weld center is decreased while the ductility is enhanced. The tensile strength and yield strength in the weld nugget zone and thermo-mechanically affected zone are significantly decreased while the elongation is increased due to the change of strengthening mechanism. In the heat affected zone the strength is decreased compared to the base material because the second phase grows up.

scholarly journals Effect of Laser Peening on the Mechanical Properties of Aluminum Alloys Probed by Synchrotron Radiation and X-Ray Free Electron Laser

Metals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1490
Author(s):  
Yuji Sano ◽  
Kiyotaka Masaki ◽  
Koichi Akita ◽  
Kentaro Kajiwara ◽  
Tomokazu Sano
Keyword(s):  
Aluminum Alloy ◽  
Synchrotron Radiation ◽  
Free Electron ◽  
Free Electron Laser ◽  
Fatigue Cracks ◽  
Three Dimensional ◽  
Fatigue Loading ◽  
Laser Peening ◽  
X Ray ◽  
Friction Stir

Synchrotron radiation (SR) and X-ray free electron laser (XFEL) are indispensable tools not only for the exploration of science but also for the evolution of industry. We used SR and XFEL to elucidate the mechanism and the effects of laser peening without coating (LPwC) which enhances the durability of metallic materials. X-ray diffraction (XRD) employing SR revealed that the residual stress (RS) in the top surface became compressive as the laser pulse irradiation density increased with appropriate overlapping of adjacent laser pulses. SR-based computed tomography (CT) was used to nondestructively reconstruct three-dimensional (3D) images of fatigue cracks in aluminum alloy, revealing that LPwC retarded crack propagation on the surface and inside of the sample. SR-based computed laminography (CL) was applied to friction stir welded (FSWed) aluminum alloy plates to visualize fatigue cracks propagating along the welds. The fatigue crack had complicated shape; however, it became a semi-ellipsoid once projected onto a plane perpendicular to the fatigue loading direction. Ultra-fast XRD using an XFEL was conducted to investigate the dynamic response of aluminum alloy to an impulsive pressure wave simulating the LPwC condition. The diffraction pattern changed from spotty to smooth, implying grain refinement or subgrain formation. Shifts in diffraction angles were also observed, coinciding with the pressure history of laser irradiation. The durations of the dynamic phenomena were less than 1 µs; it may be possible to use high-repetition lasers at frequencies greater than kHz to reduce LPwC processing times.

scholarly journals Effect of Corrosion and Surface Finishing on Fatigue Behavior of Friction Stir Welded EN AW-5754 Aluminum Alloy Using Various Tool Configurations

Materials ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3121 ◽  
Author(s):  
Abootorab Baqerzadeh Chehreh ◽  
Michael Grätzel ◽  
Jean Pierre Bergmann ◽  
Frank Walther
Keyword(s):  
Climate Change ◽  
Aluminum Alloy ◽  
Fatigue Behavior ◽  
Salt Spray ◽  
Base Material ◽  
Fatigue Properties ◽  
Surface Finishing ◽  
Friction Stir ◽  
Stationary Shoulder ◽  
Root Surfaces

In this study, fatigue behavior of surface finished and precorroded friction stir welded (FSW) specimens using various tool configurations were comparatively investigated by the load increase method. The FSW using conventional, stationary shoulder and dual-rotational configurations was carried out by a robotized tool setup on 2 mm EN AW-5754 aluminum sheets in butt joint formation. After extraction of the specimens, their weld seam and root surfaces were milled to two different depths of 200 µm and 400 µm to remove the surface and the FSW tool shoulder effects. This surface finishing process was performed to investigate the effect of the surface defects on the fatigue behavior of the FSW EN AW-5754 aluminum alloy sheets. It was found that material removal from the weld and root surfaces of the specimens, increased the fracture stresses of conventional and dual-rotational FSW from 204 to 229 MPa and 196 to 226 MPa, respectively. However, this increase could not be detected in stationary shoulder FSW. Specimens with finished surfaces, which showed superior properties, were used in salt spray and cyclic climate change test to investigate the effect of corrosion on the fatigue behavior of FSW specimens. It was shown that cyclic climate change test reduced the fatigue properties of the base material, conventional, stationary shoulder and dual-rotational FSW approximately 1%–7%. This decrease in the fatigue properties was greater in the case of the salt spray test, which was 7% to 21%.

scholarly journals Fatigue Modeling Containing Hardening Particles and Grain Orientation for Aluminum Alloy FSW Joints

Materials ◽  
2019 ◽  
Vol 12 (12) ◽  
pp. 2024 ◽  
Author(s):  
Guoqin Sun ◽  
Yicheng Guo ◽  
Xiuquan Han ◽  
Deguang Shang ◽  
Shujun Chen
Keyword(s):  
Aluminum Alloy ◽  
Grain Orientation ◽  
Base Material ◽  
Correlation Method ◽  
Stress Transfer ◽  
Macroscopic Model ◽  
Fatigue Properties ◽  
Isotropic Hardening ◽  
Stress And Strain ◽  
Friction Stir

The macro-mesoscopic joint fatigue model containing hardening particles and crystal characteristics is established to study the effect of the hardening particles and the grain orientation on fatigue properties of an aluminum alloy friction stir welding (FSW) joint. The macroscopic model is composed of the weld nugget zone, thermo-mechanically affected zone, heat-affected zone, and base material, according to the metallurgical morphology and hardness distribution of the joint. Cyclic stress and strain data are used to determine the material properties. The fatigue parameters used in the calculation of cyclic stresses and strains are obtained with the four-point correlation method. The mesoscopic models of different zones are inserted into the joint macroscopic model as submodules. The models containing the information of hardening particles and grain orientation are established with crystal plasticity theory for the grains and isotropic hardening rule for the hardening particles. The effects of hardening particles and grain orientation on the stress and strain responses are discussed. The simulation results show that high-angle misorientation of adjacent grains hinders the stress transfer. The particle cluster or cracked particles intensify the stress and strain concentrations.

scholarly journals Microstructure and Low Cycle Fatigue Properties of AA5083 H111 Friction Stir Welded Joint

Materials ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2381 ◽  
Author(s):  
Janusz Torzewski ◽  
Krzysztof Grzelak ◽  
Marcin Wachowski ◽  
Robert Kosturek
Keyword(s):  
Aluminum Alloy ◽  
Tensile Properties ◽  
Low Cycle Fatigue ◽  
Fatigue Cracks ◽  
Base Material ◽  
Welding Parameters ◽  
Cycle Fatigue ◽  
Butt Joints ◽  
Friction Stir ◽  
Secondary Cracks

The present paper aims to analyze the microstructure, microhardness, tensile properties, and low cycle fatigue (LCF) behavior of friction stir welded (FSW) butt joints. The material used in this study was the 5 mm thick 5083 H111 aluminum alloy sheet. Butt joints of AA 5083 H111 were manufactured at different operating parameters of the FSW process. The effect of the welding parameters on microstructure, microhardness, and tensile properties was investigated. Based on microstructure analysis and strength tests, the most favorable parameters of the FSW process were settled on the point of view of weld quality. Then, LCF tests of base material and friction stir welded specimens made of 5083 H111 were carried out for the examined welded samples under selected friction stir welding parameters. The process of low-cycle fatigue of 5083 H111 aluminum alloy was characterized by cyclic hardening for both: base material and FSW joint. It was revealed by a decrease in the width of the hysteresis loop with the simultaneous significant increase in the values of the range of stress. It was determined that fatigue cracks are initiated by cyclic slip deformation due to local stress concentration from the surface in the corner of the samples for the base material and the heat-affected zone for FSW joints. For all tested strain amplitudes, the fatigue crack propagation region is characterized by the presence of fatigue striation with secondary cracks.

The Fatigue Properties of Laser Shock Processed Aluminum Alloy 7050

2007 ◽  
Author(s):  
Shikun Zou ◽  
Ziwen Cao
Keyword(s):  
Residual Stress ◽  
Aluminum Alloy ◽  
Fatigue Life ◽  
Plastic Strain ◽  
Base Material ◽  
Fatigue Properties ◽  
Hole Drilling ◽  
Drilling Process ◽  
Laser Peening ◽  
Laser Shock

In order to develop the application of laser shock processing (also named laser peening or LSP in short) as a strengthening technology for 7050 aluminum alloy fastener holes, the fatigue properties of laser shock-processed aluminum alloy specimens were investigated. At first, the dislocation density and surface residual stress induced in the shock affected zone was characterized and compared with that of the base material. Then, the fatigue specimens with stress-concentration hole (notch) were treated by LSP. The fatigue life of LSP-treated specimens were measured and compared with that of specimens made from base material without LSP. Fatigue tests were taken under special flight spectrum loading condition for mid-airframe. The results indicated that laser peening improved the fatigue life of all specimens tested. Specimens treated by LSP before hole-drilling had longer fatigue life than those specimens treated by LSP after hole-drilling. At last, the difference of both sequences was investigated by analyzing the plastic strain and residual stress induced by LSP. LSP induced both plastic strain and deformation at the surface layer. The plastic strain induced by LSP was shown to produce harmful orifices with sharp-angle near the edge of hole. The residual stress induced by LSP appears to remain compressive even after the hole-drilling process. In average, the fatigue life of specimens treated by LSP before hole-drilling was found to be 173% longer than that of untreated samples and approaching the life enhancement factor demonstrated by rod extrusion method (on specimens with large diameter holes).

Effect of Welding Speeds on Mechanical Properties of Level Compensation Friction Stir Welded 6061-T6 Aluminum Alloy

2016 ◽  
Vol 35 (4) ◽  
pp. 375-379 ◽  
Author(s):  
Quan Wen ◽  
Yumei Yue ◽  
Shude Ji ◽  
Zhengwei Li ◽  
Shuangsheng Gao
Keyword(s):  
Aluminum Alloy ◽  
Welding Speed ◽  
Weld Zone ◽  
Base Material ◽  
Tensile Fracture ◽  
Tool Rotational Speed ◽  
Friction Stir ◽  
Fracture Position ◽  
Transverse Tensile ◽  
Equal Thickness

AbstractIn order to eliminate the flash, arc corrugation and concave in weld zone, level compensation friction stir welding (LCFSW) was put forward and successfully applied to weld 6061-T6 aluminum alloy with varied welding speed at a constant tool rotational speed of 1,800 rpm in the present study. The glossy joint with equal thickness of base material can be attained, and the shoulder affected zone (SAZ) was obviously reduced. The results of transverse tensile test indicate that the tensile strength and elongation reach the maximum values of 248 MPa and 7.1% when the welding speed is 600 mm/min. The microhardness of weld nugget (WN) is lower than that of base material. The tensile fracture position locates at the heat affected zone (HAZ) of the advancing side (AS), where the microhardness is the minimum. The fracture surface morphology represents the typical ductile fracture.

Investigation on the Corrosion Effect of Friction Stir Welded AA2024 T3 Aluminum Alloy Joints

2012 ◽  
Vol 525-526 ◽  
pp. 129-132 ◽  
Author(s):  
Yu E Ma ◽  
Zhen Qiang Zhao
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Aluminum Alloy ◽  
Welded Joint ◽  
Weld Zone ◽  
Base Material ◽  
Localized Corrosion ◽  
Aircraft Structure ◽  
Friction Stir ◽  
Scanning Electron

Before friction stir welded integral panels are used in main aircraft structure, the corrosion behavior of welded joint need to be studied in detail. 2024 T3 samples were designed and welded by friction stir welding; the microstructure crossing the weld zone was observed by scanning electron microscopy (SEM), the feature of different zones (base material, thermo-mechanical affected zone, nugget) was seen; the corrosion testing in NaCl smoking box was carried out, and microstructure was observed after corrosion, localized corrosion predominantly occurs in the thermo-mechanical affected zone.

scholarly journals Mechanical and Microstructural Characterization of Friction Stir Welded SiC and B4C Reinforced Aluminium Alloy AA6061 Metal Matrix Composites

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3110
Author(s):  
Kaveripakkam Suban Ashraff Ali ◽  
Vinayagam Mohanavel ◽  
Subbiah Arungalai Vendan ◽  
Manickam Ravichandran ◽  
Anshul Yadav ◽  
...  
Keyword(s):  
Wear Rate ◽  
Aluminium Alloy ◽  
Metal Matrix Composites ◽  
Metal Matrix ◽  
Weld Zone ◽  
Base Material ◽  
Matrix Composites ◽  
Wear Properties ◽  
Friction Stir ◽  
Behavioural Aspects

This study focuses on the properties and process parameters dictating behavioural aspects of friction stir welded Aluminium Alloy AA6061 metal matrix composites reinforced with varying percentages of SiC and B4C. The joint properties in terms of mechanical strength, microstructural integrity and quality were examined. The weld reveals grain refinement and uniform distribution of reinforced particles in the joint region leading to improved strength compared to other joints of varying base material compositions. The tensile properties of the friction stir welded Al-MMCs improved after reinforcement with SiC and B4C. The maximum ultimate tensile stress was around 172.8 ± 1.9 MPa for composite with 10% SiC and 3% B4C reinforcement. The percentage elongation decreased as the percentage of SiC decreases and B4C increases. The hardness of the Al-MMCs improved considerably by adding reinforcement and subsequent thermal action during the FSW process, indicating an optimal increase as it eliminates brittleness. It was seen that higher SiC content contributes to higher strength, improved wear properties and hardness. The wear rate was as high as 12 ± 0.9 g/s for 10% SiC reinforcement and 30 N load. The wear rate reduced for lower values of load and increased with B4C reinforcement. The microstructural examination at the joints reveals the flow of plasticized metal from advancing to the retreating side. The formation of onion rings in the weld zone was due to the cylindrical FSW rotating tool material impression during the stirring action. Alterations in chemical properties are negligible, thereby retaining the original characteristics of the materials post welding. No major cracks or pores were observed during the non-destructive testing process that established good quality of the weld. The results are indicated improvement in mechanical and microstructural properties of the weld.

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