The Effect of Microstructural and Geometrical Features on Fatigue Performance in Mg AZ31 Friction Stir Spot Welds

2011 ◽  
Author(s):  
J. B. Jordon
Keyword(s):  
Optical Microscopy ◽  
Weld Zone ◽  
Sheet Thickness ◽  
Fatigue Performance ◽  
Welding Parameters ◽  
Spot Welds ◽  
Friction Stir ◽  
Lap Shear ◽  
Nugget Diameter ◽  
Geometrical Features

The relationship of microstructural and geometrical features to fatigue performance is investigated in friction stir spot welds made using AZ31 magnesium alloy sheets. Lap-shear coupons were spot welded using two sets of welding parameters. Optical microscopy of the initial state of the microstructure of each set of spot welds revealed differences in the hook formation, sheet thickness in the weld zone, and nugget diameter. Both sets of welds were fatigue tested in load control until failure at various load ratios. Optical microscopy of the failed coupons revealed differences in the fracture mode between the two sets of coupons. A linear elastic fracture mechanics model was used to correlate the fatigue life in the two processes. The fatigue model, which is a function of hook size, sheet thickness, and nugget diameter, showed good correlation to the experimental results. The model was also employed to show that the fatigue of the friction stir spot welds was most sensitive to the sheet thickness in the weld zone, followed by hook height, and then nugget diameter.

Effects of bottom plate in friction stir welding of AA6061-T6

2020 ◽  
Vol 118 (1) ◽  
pp. 108
Author(s):  
M.A. Vinayagamoorthi ◽  
M. Prince ◽  
S. Balasubramanian
Keyword(s):  
Mechanical Properties ◽  
Axial Load ◽  
Weld Zone ◽  
Welding Process ◽  
Bottom Plate ◽  
Welding Parameters ◽  
Nugget Zone ◽  
Friction Stir ◽  
Weld Joints ◽  
Fine Grain

The effects of 40 mm width bottom plates on the microstructural modifications and the mechanical properties of a 6 mm thick FSW AA6061-T6 joint have been investigated. The bottom plates are placed partially at the weld zone to absorb and dissipate heat during the welding process. An axial load of 5 to 7 kN, a rotational speed of 500 rpm, and a welding speed of 50 mm/min are employed as welding parameters. The size of the nugget zone (NZ) and heat-affected zone (HAZ) in the weld joints obtained from AISI 1040 steel bottom plate is more significant than that of weld joints obtained using copper bottom plate due to lower thermal conductivity of steel. Also, the weld joints obtained using copper bottom plate have fine grain microstructure due to the dynamic recrystallization. The friction stir welded joints obtained with copper bottom plate have exhibited higher ductility of 8.9% and higher tensile strength of 172 MPa as compared to the joints obtained using a steel bottom plate.

Fatigue Behavior of Magnesium AZ31 in Friction Stir Spot Welds

2009 ◽  
Author(s):  
J. B. Jordon ◽  
M. F. Horstemeyer ◽  
H. Badarinarayan ◽  
J. Grantham
Keyword(s):  
Fatigue Life ◽  
Crack Growth ◽  
Fatigue Behavior ◽  
Spot Welds ◽  
Friction Stir ◽  
Lap Shear ◽  
Magnesium Az31 ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes ◽  
Crack Growth Modeling

In this study, the fatigue behavior of AZ31 magnesium friction stir spot welded joints is experimentally investigated. The friction stir spot welds employed here are representative of preliminary welds made in developing the joining process for potential use in automobile manufacturing. Load control cyclic tests were conducted on single weld lap-shear coupons and were fatigued until failure to determine stress-life properties. The fractured coupons were examined under optical and scanning electron microscopes with the intent to determine fatigue crack characteristics. Fractography analysis suggests that long crack growth accounts for a majority of the fatigue life. To predict the fatigue life of the lap-joint coupons, a long crack growth modeling approach, based on a kinked crack stress intensity solution, was employed. The fatigue model predictions compared well to the experimental stress-life results.

scholarly journals Improvement on Mechanical Properties of Submerged Friction Stir Joining of Dissimilar Tailor Welded Aluminum Blanks

2021 ◽  
Vol 2021 ◽  
pp. 1-6
Author(s):  
R. Suryanarayanan ◽  
V. G. Sridhar ◽  
L. Natrayan ◽  
S. Kaliappan ◽  
Anjibabu Merneedi ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Friction Stir Welding ◽  
Mechanical Performance ◽  
Weld Zone ◽  
Tensile Tests ◽  
Welding Parameters ◽  
Negative Effects ◽  
Friction Stir ◽  
Tailor Welded Blanks ◽  
Secondary Precipitates

Friction stir welding is a solid-state welding method that produces joints with superior mechanical and metallurgical properties. However, the negative effects of the thermal cycle during welding dent the mechanical performance of the weld joint. Hence, in this research study, the joining of aluminum tailor welded blanks by friction stir welding is carried out in underwater conditions by varying the welding parameters. The tensile tests revealed that the underwater welded samples showed better results when compared to the air welded samples. Maximum tensile strength of 229.83 MPa was obtained at 1000 rpm, 36 mm/min. The improved tensile strength of the underwater welded samples was credited to the suppression of the precipitation of the secondary precipitates due to the cooling action provided by the water. The lowest hardness of 72 HV was obtained at the edge of the stir zone which indicated the weakest region in the weld zone.

scholarly journals The Influence of Tool Wear on the Mechanical Performance of AA6061-T6 Refill Friction Stir Spot Welds

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7252
Author(s):  
Willian S. de Carvalho ◽  
Maura C. Vioreanu ◽  
Maxime R. A. Lutz ◽  
Gonçalo P. Cipriano ◽  
Sergio T. Amancio-Filho
Keyword(s):  
Tool Wear ◽  
Mechanical Performance ◽  
Welding Parameters ◽  
Fracture Mechanisms ◽  
Friction Stir ◽  
Lap Shear ◽  
Tool Wear Mechanisms ◽  
Local Mechanical Property ◽  
Property Changes ◽  
Aluminum And Magnesium Alloys

The Refill Friction Stir Spot Welding (RFSSW) process—an alternative solid-state joining technology—has gained momentum in the last decade for the welding of aluminum and magnesium alloys. Previous studies have addressed the influence of the RFSSW process on the microstructural and mechanical properties of the AA6061-T6 alloy. However, there is a lack of knowledge on how the tool wear influences the welding mechanical behavior for this alloy. The present work intended to evaluate and understand the influence of RFSSW tool wear on the mechanical performance of AA6061-T6 welds. Firstly, the welding parameters were optimized through the Designing of Experiments (DoE), to maximize the obtained ultimate lap shear force (ULSF) response. Following the statistical analysis, an optimized condition was found that reached a ULSF of 8.45 ± 0.08 kN. Secondly, the optimized set of welding parameters were applied to evaluate the wear undergone by the tool. The loss of worn-out material was systematically investigated by digital microscopy and the assessment of tool weight loss. Tool-wear-related microstructural and local mechanical property changes were assessed and compared with the yielded ULSF, and showed a correlation. Further investigations demonstrated the influence of tool wear on the height of the hook, which was located at the interface between the welded plates and, consequently, its effects on the observed fracture mechanisms and ULSF. These results support the understanding of tool wear mechanisms and helped to evaluate the tool lifespan for the selected commercial RFSSW tool which is used for aluminum alloys.

scholarly journals Friction Stir Spot Welding with Additional Bonding of Thick Sheet Aluminum Joints

Metals ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 732 ◽  
Author(s):  
Marcel Hatzky ◽  
Antonia Frank ◽  
Stefan Böhm
Keyword(s):  
Aluminum Alloys ◽  
Spot Welding ◽  
Sheet Thickness ◽  
High Strength ◽  
Friction Stir Spot Welding ◽  
Glass Beads ◽  
Welding Parameters ◽  
Thick Sheet ◽  
Friction Stir ◽  
Body Construction

The high-strength aluminum alloys offer great potential for realizing lightweight constructions in car body construction. However, the use of aluminum alloys increases the overall thickness of the material, which poses new challenges for potential joining processes. This paper examines a process combination of friction stir spot welding (FSSW) and bonding for 4 mm EN AW 6082-T6 sheets. For the investigations, adhesive or glass beads were applied between the joining components and then the sheets were welded using FSSW. The analysis shows that the adhesive and the glass beads have a very small influence on the joint formation. The use of glass beads in FSSW with bonding is recommended because less adhesive is displaced from the joint area, which increases the joint strength. The target of obtaining high weld spot strengths without strength-reducing adhesive burn-off could not be achieved because a certain residence time is necessary to form a weld spot with high strength at this sheet thickness in order to sufficiently plasticize the material. Adhesive burn-up cannot be completely avoided. For this reason, it is necessary to weigh up which characteristics are required for the specific application and adjust the welding parameters accordingly.

Investigation of geometrical features on mechanical properties of AA2198 refill friction stir spot welds

2018 ◽  
Vol 36 ◽  
pp. 330-339 ◽  
Author(s):  
Camila Caroline de Castro ◽  
Athos Henrique Plaine ◽  
Gabriel Pietta Dias ◽  
Nelson Guedes de Alcântara ◽  
Jorge Fernandez dos Santos
Keyword(s):  
Mechanical Properties ◽  
Spot Welds ◽  
Friction Stir ◽  
Geometrical Features

Friction Stir Spot Welds between Aluminium and Steel Automotive Sheets: Influence of Welding Parameters on Mechanical Properties and Microstructure

2009 ◽  
Vol 53 (1-2) ◽  
pp. R13-R23 ◽  
Author(s):  
Gunter Figner ◽  
Rudolf Vallant ◽  
Thomas Weinberger ◽  
Norbert Enzinger ◽  
Hartmuth Schröttner ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Welding Parameters ◽  
Spot Welds ◽  
Friction Stir
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