• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.05a
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• pp.242-243
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• 2009

Friction stir welding and friction stir processing is a new solid state processing technique for ioining and micro..structural modification in metallic materials. It has been applied not only joining for light metals but also modification of the microstructure to enhance mechanical properties. In thin study, we investigated the mechanical properties for applied friction stir welding and processing under various parameters such as probe diameter, probe type, traveling speed and rotating speed for 5456-H116 AI allov. As a result of experiments, optimum condition of friction stir welding is traveling speed of 15mm/min, rotating speed of 500RPM at 6mm diameter probe. Moreover, in the case of friction stir processing, the optimum condition is traveling speed of 15mm/min, rotating speed of 250RPM at full screw probe. As above mentioned, the mechanical characteristics enhanced with the decreasing of traveling speed and the increasing of friction areas because of plastic flow due to high friction heat. These result can be used as reference data for ship repairment.

• Journal of the Korean institute of surface engineering
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• v.42 no.1
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• pp.13-20
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• 2009

Friction stir welding(FSW) was developed as a new solid state welding technique by The Welding Institute (TWI). On the basis of FSW, a new processing technique, friction stir processing (FSP), has recently been developed. FSP has been applied to cast aluminum alloy to modify the microstructure to enhance mechanical characteristic. FSP is a new solid state processing technique for microstructural modification in metallic materials. FSP has been applied to aluminum alloy to modify the microstructure to enhance mechanical characteristic. In this study, we investigated optimum condition friction stir processing with the evaluation of mechanical characteristic for 5456-H116 Al alloy. The mechanical characteristics of base metal similar with in 15 mm/min, 250 RPM with full screw probe. This condition is concluded that optimum friction stir processing condition. The result of this investigation will be able to application for repair of welding part for aluminum ship.

• Journal of Welding and Joining
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• v.31 no.2
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• pp.26-29
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• 2013

The latest research & development trend on friction stir welding and friction stir processing technologies presented in the international symposium, 'Friction Stir Welding & Processing VII'. Papers and presentations about high temperature materials such as advanced high strength steel, stainless steel and titanum alloy shoot up this year. Papers on modeling of metal flow and control of process parameters also increased. The FSP technologies for manufacturing of carbon materials reinforced metal matrix composites were reported, too.

• Journal of Welding and Joining
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• v.30 no.5
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• pp.27-33
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• 2012

Friction stir processing (FSP), developed based on the basic principles of friction stir welding(FSW), a solid-state joining process originally developed for various metal alloys, is an emergingmetalworking technique that can provide localized modification and control of microstructures in near-surface layers of processed metallic components. The FSP causes intense plastic deformation, material mixing, and thermal exposure, resulting in significant microstructural refinement, densification, and homogeneity of the processed zone. The FSP technique has been successfully used for producing the fine-grained structure and surface composite, modifying the microstructure of materials, and synthesizing the composite and intermetallic compound in situ. In this review article, the current state of the understanding and development of FSP is addressed.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.534-538
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• 2002

Dissimilar friction stir welding of aluminum (AI) alloy 1050 and magnesium (Mg) alloy AZ31 was successfully done in the limited welding parameters. The dissimilar weld showed good quality and facility compared to conventional fusion weld. Transverse cross section perpendicular to the welding direction had no defects. The weld was divided into base material of Al alloy, an irregular shaped stir zone and base material of Mg alloy. The irregular shaped stir zone was roughly located around the initial weld center. The weld interface near plate surface shifted from initial weld centerline to the advancing side. Hardness profile of the weld was heterogeneous, and the hardness value of the stir zone was raised to about 150 Hv to 250 Hv. The mixed phase was identified to intermetallic compound $Mg_{17}$Al$_{12}$ using x-ray diffraction method, energy dispersive x-ray spectroscopy (EDX) and electron probe micro analysis (EPMA). The formation of intermetallic compound $Mg_{17}$Al$_{12}$ during FSW causes the remarkable increase in hardness value in the stir zone.one.

• Transactions of Materials Processing
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• v.24 no.4
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• pp.256-263
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• 2015

Electric resistance spot welding has been used to join overlapped steel sheets in automotive bodies. Recently to reduce weight in automotive vehicles, non-ferrous metals are being used or considered in car bodies for hoods, trunk lids, doors parts, etc. Various welding processes such as laser welding, self-piercing rivet, friction stir welding are being used. In the current study, a new electric resistance heated friction stir spot welding is suggested for the spot welding of non-ferrous metals. The welding method can be characterized by three uses of heat -- electric resistance heating, friction stir heating and conduction heating of steel electrodes -- for the fusion joining at the interfacial zone between the two sheets. The welding process has variables such as welding current, diameter of the steel electrodes, revolutions per minute (rpm) of the friction stir pin, and the insert depth of the stir pin. In order to obtain the optimal welding variables, which provide the best welding strength, many experiments were conducted. From the experiments, it was found that the welding strength could be reached to the required production value by using an electrode diameter of 10mm, a current of 7.6kA, a stirring speed of 400rpm, and an insert depth of 0.8mm for the electric resistance heated friction stir spot welding of 5052 aluminum 1.5mm sheets.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.493-498
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• 2002

Friction stir welding (FSW) is a relatively new solid-state joining process which can homogenize the heterogeneous microstructure by intensely plastic deformation arising from the rotation of the welding tool. The present study applied the FSW to an A356 aluminum (AI) alloy with the as-cast heterogeneous microstructure in the T6 temper condition, and examined an effect of microstructure on mechanical properties in the weld. The base material consisted of Al matrix with a high density of strengthening precipitates, large eutectic silicon and a lot of porosities. The FSW led to fragment of the eutectic silicon, extinction of the porosities and dissolution of the strengthening precipitates in the Al alloy. The dissolution of strengthening precipitates reduced the hardness of the weld around the weld center and the transverse ultimate tensile strength of the weld. Longitudinal tensile specimen containing only the stir zone showed the roughly same strength as the base material and a much larger elongation. Moreover, Charpy impact tests indicated that the stir zone had remarkably the higher absorbed energy than the base material. The higher mechanical properties of the stir zone were attributed to a homogenization of the as-cast heterogeneous microstructure by FSW.

• Journal of Welding and Joining
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• v.31 no.4
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• pp.73-79
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• 2013

Burr grinding, Tungsten Inert Gas (TIG) dressing, ultrasonic impact treatment, and peening are used to improve fatigue life in steel structures. These methods improve the fatigue life of weld joints by hardening the weld toe, by improving the bead shape, and by creating the compressive residual stress. In this study, a new post-weld treatment method improving the weld bead shape and metal structure at the welding zone using Friction Stir Processing (FSP), a welding process, is proposed to enhance fatigue life. For that, a pin-shaped tool and processing condition employing Friction Stir Processing (FSP) is established through experiments. Experimental results revealed that fatigue life is improved by around 50% compared to as-welded fatigue specimens by reducing the stress concentration at the weld toe and by generating a metal structure finer than that of flux-cored arc welding (FCAW).

• Proceedings of the KWS Conference
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• 2005.06a
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• pp.384-386
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• 2005

Initial oxide layer on the butt surface fragments during friction stir welding (FSW) and then often remains as a faint zigzag-line pattern on the cross section. When remnant of the oxide layer often adversely affects the mechanical properties in the weld, it is called as 'kissing-bond'. The present study systematically examines effect of oxide array on bend property in the root of friction stir (FS) welded Al alloy 1050 by transmission electron microscopy (TEM), and then clarifies identity of the kissing-bond.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.239-242
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• 2009

Friction stir spot welding (FSSW), developed based on principle of friction stir welding, has been paid attention as a new solid-state spot welding process. Since FSSW can produce high-quality weld in Al alloys more easily than resistance spot welding, this process has been already used for construction of Al components in the automotive industries. Despite the large industrial interests in FSSW, fundamental knowledge on welding phenomena of this process has not been fully understood. In this study, FSSW phenomena, such as the consolidation mechanism, the microstructural evolution and the material flow, were examined in Al alloy 6061. This study clarified that the elliptical zone found in the vicinity of the pin hole on the cross section was characterized by the initially lapped surface of two sheets. Moreover, the following material flow was proposed; capture of the upper material with the threads on the pin surface, spiral flow along the tool rotation, and then release at the tip of the pin.