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Öğe The effect of weld parameters on friction stir welding of brass plates(Wiley-V C H Verlag Gmbh, 2008) Cam, G.; Serindag, H. T.; Cakan, A.; Mistikoglu, S.; Yavuz, H.More successful results have been obtained in butt- and overlap-joining of Al-alloy plates by a recently developed solid state joining technique, namely friction stir welding (FSW), than in more conventional fusion welding processes. In this joining technique, no fusion takes place in the joint area of the plates welded. This novel joining method also offers the potential to weld some other materials rather than Al-alloys, such as Mg-alloys, brasses and low strength steels. In this study, the applicability of friction stir welding to brasses, namely 90%Cu-10%Zn and 70%Cu-30%Zn alloys, has been investigated. The joint performance was determined by conducting optical microscopy, microhardness mesurements and mechanical testing (e.g. tensile and bend tests). The effect of welding speed on the joint quality at a given rotational speed of the stirring pin (i.e. 1600 rpm) was also determined for both alloys. The highest joint performances were obtained at a welding speed of 210 mm/min for both alloys.Öğe Effect of welding parameters on lap shear tensile properties of dissimilar friction stir spot welded AA 5754-H22/2024-T3 joints(Taylor & Francis Ltd, 2013) Bozkurt, Y.; Salman, S.; Cam, G.In this study, the effect of weld parameters on mechanical properties, such as lap shear fracture load, of friction stir spot welded dissimilar lap joints was studied. The effects of the plate positioning, the plunge depth and the dwell time as well as the tool tilt angle on the joint strength were investigated. The experimental results showed that the positioning of the sheets played an important role on the strength of the joints. The joint strength was higher when AA 5754 sheet is placed on the top, whereas lower strength values were displayed by dissimilar joints produced by placing AA 2024 as the upper sheet. It was also observed that the plunge depth, dwell time and tool tilt angle had a strong effect on the failure mode of the friction stir spot welded lap joints produced. The joints exhibited two different fracture modes, namely cross and pullout nugget under lap shear tensile testing conditions.Öğe Effects of use of higher strength interlayer and external cooling on properties of friction stir welded AA6061-T6 joints(Taylor & Francis Ltd, 2014) Cam, G.; Ipekoglu, G.; Serindag, H. TarikAlthough sound AA6061-T6 joints can be produced by friction stir welding, a loss in strength takes place in the weld region. In this study, it was demonstrated that the strength of the nugget could be increased by the use of a higher strength interlayer during friction stir welding. This strength recovery cannot, however, be attainable in the heat affected zone. Although an external cooling was applied during welding in order to increase strength in the heat affected zone, it was not sufficient for achieving the required cooling condition for improved strength.Öğe Friction stir welded structural materials: beyond Al-alloys(Taylor & Francis Ltd, 2011) Cam, G.The friction stir welding (FSW) technique is widely accepted to be one of the most significant welding techniques to emerge in the last 20 years. Friction stir welding of Al-alloys is now commonplace and is covered in several recent reviews, including one in this journal. Consequently, the technique is currently being used for joining of these alloys in various industrial applications. Complementary to these developments has been a dramatic increase in research into joining of other alloys and systems by FSW. This field is very active, but less mature. Thus, the aim of this review article is to build on our understanding of the fundamentals, as applied to Al-alloys that laid out in the previous review in this journal, and to address the current state-of-the-art of FSW developing beyond Al-alloys, including Mg-alloys, Cu-alloys, steels, Ti-alloys and metal matrix composites, focusing particularly on microstructural aspects, including texture formation, and the resulting properties of these joints. Material selection for tooling will also be covered to some extent while modelling studies of material flow during FSW are outside the scope of this paper. Finally, residual stresses are mentioned in a number of places and while these have been measured extensively for Al-alloy systems there are fewer measurements for other systems.Öğe Investigation into the effect of temper condition on friction stir weldability of AA6061 Al-alloy plates(Redakcia Kovove Materialy, 2013) Ipekoglu, G.; Erim, S.; Kiral, B. Goren; Cam, G.Although Al-alloys have been widely applied in transportation industries in recent years owing to their low density and excellent formability properties, further advancement in welding of these alloys is a very critical issue for further increasing their use in practice. These alloys, which exhibit difficulties in fusion welding processes, particularly age-hardened grades, can be successfully joined by friction stir welding. In this study, AA6061 Al-alloy plates both in 0 and T6 temper conditions were joined by friction stir welding using four different sets of weld parameters. Microstructural and mechanical characterization of the joints produced was made by detailed optical microscopy investigations, extensive hardness measurements and tensile tests. The effect of temper condition on the joint performance was also determined in addition to the effect of weld parameters on the joint quality.Öğe Investigation into the microstructure and mechanical properties of diffusion bonded TiAl alloys(Springer, 2006) Cam, G.; Ipekoglu, G.; Bohm, K. -H.; Kocak, M.TiAl alloys are potential candidates for replacing conventional Ti-alloys in gas turbine applications in the relatively lower temperature sections, owing to their low density and excellent high temperature properties. However, their intolerable ambient temperature brittleness hinders their use in such applications. Recently, TiAl alloys with some room temperature ductility were developed through alloy development programmes using special production routes such as powder metallurgy. However, the room temperature brittleness of these alloys could not be overcome. Sound joining of these alloys is a fundamental prerequisite for their successful integration into high temperature aerospace applications. It has been well demonstrated that diffusion bonding, a commonly used joining technology in conventional Ti-alloys, can successfully be used in joining of TiAl alloys both in as-cast or special-rolled conditions. In this study, diffusion bondability of a recently developed C containing TiAl alloy with a duplex microstructure using bonding parameters in the range of commercially available equipments was studied. Microstructural investigations in the joint area of the bonds were conducted to observe the presence of any weld defect. Additionally, the mechanical behaviour of the bonds was determined by shear testing to find out the optimum bonding parameters. Furthermore, the effect of post-bond heat treatment on the mechanical properties was investigated.Öğe Mechanical properties of friction stir butt-welded Al-5086 H32 plate(Wiley-V C H Verlag Gmbh, 2009) Cam, G.; Gucluer, S.; Cakan, A.; Serindag, H. T.Al-5086 H32 plates with a thickness of 3 mm were friction stir butt-welded using different welding speeds at a tool rotational speed of 1600 rpm. The effect of welding speed on the weld performance of the joints was investigated by conducting optical microscopy, microhardness measurements and mechanical tests (i.e. tensile and bend tests). The effect of heat input during friction stir welding on the microstructure, and thus mechanical properties, of cold-rolled Al- 5086 plates was also determined. The experimental results indicated that the maximum tensile strength of the joints, which is about 75% that of the base plate, was obtained with a traverse speed of 200 mm/min at the tool rotational speed used, e.g. 1600 rpm, and the maximum bending angle of the joints can reach 180 degrees. The maximum ductility performance of the joints was, on the other hand, relatively low, e.g. about 20%. These results are not unexpected due to the loss of the cold-work strengthening in the weld region as a result of the heat input during welding, and thus the confined plasticity within the stirred zone owing to strength undermatching. Higher joint performances can also be achieved by increasing the penetration depth of the stirring probe in butt-friction stir welding of Al-5086 H32 plates.Öğe Microstructural and mechanical characterization of diffusion bonded hybrid joints(Springer, 2008) Cam, G.; Ozdemir, U.; Ventzke, V.; Kocak, M.Ti-alloys, particularly TiAl, are becoming attractive for the use in the production of high-temperature components such as turbine blades and exhaust valves, owing to their low density. However, these components may not be cost-effectively cast totally from TiAl alloys and casting defects may occur in investment casting of these complex parts. Other manufacturing technologies, such as machining, cannot be economically employed in these very hard and brittle materials. Production of bi-material or even multi-material TiAl components can therefore offer an alternative fabrication route provided that the joining and joint properties of these materials are well understood. In this study, the diffusion bondability and joint characteristics of TiAl and Ti-6Al-4V alloys were studied. These two different materials were joined by using various bonding parameters. Metallographic investigations were conducted for characterization of the interface region of these dissimilar joints. Furthermore, the mechanical behavior of the bond interface was evaluated by shear testing. Both results on the microstructural and mechanical characterization provided the optimum bonding conditions for the production of TiAl-Ti6Al4V hybrid joints.Öğe Microstructural and mechanical characterization of electron beam welded Al-alloy 7020(Springer, 2007) Cam, G.; Kocak, M.The electron beam (EB) welding process is used to weld any metal that can be arc welded with equal or superior weld quality. EB welding is carried out in a high-purity vacuum environment, which results in freedom from impurities such as oxides and nitrides. Thus, pore-free joints can readily be achieved in metallic materials, such as Al-alloys and Ti-alloys. However, autogenous EB welding of some aluminium alloys leads to a significant strength reduction (undermatching) in the fusion zone due to the loss of strengthening phases. For such Al-alloys, the local microstructure-property relationships should be established to satisfy the service requirement of a welded component with strength undermatching. Autogenous EB welding was performed on 5 mm thick aluminium alloy 7020 plate. Microstructural characterization of the weld metals was made by optical and scanning electron microscopy. Extensive microhardness measurements were conducted in the weld regions of the joints which exhibited a hardness loss in the fusion zone due to the loss of strengthening phases. Tensile properties of the joints were determined by testing flat transverse tensile specimens at room temperature without machining the weld profiles. Furthermore, elastic-plastic fracture toughness tests (CTOD) were carried out on the base material and welded joints at room temperature.Öğe Microstructural and Mechanical Characterization of Friction Stir Butt Joint Welded 63% Cu-37% Zn Brass Plate(Amer Welding Soc, 2009) Cam, G.; Mistikoglu, S.; Pakdil, M.A recently developed solid-state joining technique, namely friction stir welding (FSW), has been well demonstrated to produce joints with better joint performances in Al alloys, particularly in difficult-to-weld grades, than those obtained in more conventional fusion welding processes. The technique has already been implemented with joining Al alloys in various production lines such as shipbuilding, automobile, high-speed train manufacturing, and aviation industries. In this study, the applicability of friction stir welding to 63% Cu-37% Zn brass plate has been investigated. The joint performance values were determined by conducting optical microscopy, microhardness measurements, and mechanical testing (e.g., tensile and bend tests). The effects of the tool rotational speed (i.e., 1250 and 1600 rev/min) and the welding speed on the joint performance were determined. The best joint performances were obtained at a rotational speed of 1600 rev/min with a welding speed of 225 mm/min.Öğe Microstructural and mechanical characterization of laser beam welded AA6056 Al-alloy(Elsevier Science Sa, 2011) Pakdil, M.; Cam, G.; Kocak, M.; Erim, S.Laser beam welding is considered to be a suitable joining process for high speed, low distortion, and high quality fabrication of aircraft structures manufactured from aluminum alloys, which are mainly preferred due to their favourable properties, such as high strength to weight ratio, ease of forming and high thermal and electrical conductivity. However, the laser beam welding of 6000 series aluminum alloys may exhibit a tendency to solidification cracking, and porosity may be a major problem unless appropriate welding parameters and filler metal are employed. In this study, the microstructural aspects and mechanical properties of laser beam welded new generation aluminum alloy, namely 6056, developed especially for aircraft structures, are investigated. A continuous wave CO2 laser using AlSi12 filler wire was employed. A detailed microstructural examination of the weld region was carried out by Scanning Electron Microscopy (SEM). Standard tensile and microflat tensile specimens extracted from the welded plates were tested at room temperature for the determination of general and local mechanical properties of the welded joints. Extensive microhardness measurements were also conducted. Crack growth mechanisms of the joints produced were also determined by conducting fatigue tests under various stress ratios (i.e., 0.1 <= R <= 0.7). (C) 2011 Elsevier B.V. All rights reserved.
