The Experts below are selected from a list of 5409 Experts worldwide ranked by ideXlab platform
L. Zhou - One of the best experts on this subject based on the ideXlab platform.
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Enhancement in mechanical properties and corrosion resistance of 2507 duplex stainless steel via friction Stir processing
Journal of materials research and technology, 2020Co-Authors: C.y. Ma, L. Zhou, R.x. Zhang, D.g. Li, Xiaoguo Song, Y.q. ZhaoAbstract:Abstract The mechanical properties and corrosion resistance of 2507 duplex stainless steel were improved by friction Stir processing (FSP). Sound processed region was obtained with the traverse speed in the range of 50−200 mm/min and tool rotation speed of 400 rpm. The effect of traverse speed on the microstructure, mechanical properties and corrosion resistance of the processed area was analyzed. The grain size in the Stir Zone was obviously refined, and the minimum grain size was obtained at a traverse speed of 100 mm/min. The tensile strength and microhardness of the Stir Zone were higher than that of the base metal, while the elongation decreased to a certain extent. The traverse speed had little effect on the ratio of ferrite to austenite content in the processed Zone. The refined grains in the Stir Zone promoted the diffusion of elements and enhanced the stability of the passivation film, which resulted in better corrosion resistance of the Stir Zone than that of the base metal.
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Microstructural characteristics and mechanical properties of friction Stir welded joints of Ti–6Al–4V titanium alloy
Materials & Design, 2010Co-Authors: L. ZhouAbstract:Abstract The α + β titanium alloy, Ti–6Al–4V, was friction Stir welded at a constant tool rotation speed of 400 rpm. Defect-free welds were successfully obtained with welding speeds ranging from 25 to 100 mm/min. The base material was mill annealed with an initial microstructure composed of elongated primary α and transformed β. A bimodal microstructure was developed in the Stir Zone during friction Stir welding, while microstructure in the heat affected Zone was almost not changed compared with that in the base material. An increase in welding speed increased the size of primary α in the Stir Zone. The weld exhibited lower hardness than the base material and the lowest hardness was found in the Stir Zone. Results of transverse tensile test indicated that all the joints had lower strength and elongation than the base material, and all the joints were fractured in the Stir Zone.
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effect of process parameters on Stir Zone microstructure in ti 6al 4v friction Stir welds
Journal of Materials Science, 2010Co-Authors: L. ZhouAbstract:The effects of the main process variables on the Stir Zone microstructure in friction Stir welds were investigated for Ti–6Al–4V. Welds were produced by employing varying welding speeds under a constant rotation speed or different rotation speeds at a constant welding speed. The Stir Zone microstructure was examined by optical microscopy and transmission electron microscopy. It was found that the Stir Zone microstructure was determined by the parameters controlling temperature and deformation history during the friction Stir welding. A bimodal microstructure characterized by primary α and transformed β with lamellar α + β or a full lamellar microstructure composed of basket-weave α + β lamellae could be developed in the Stir Zone. The microstructural evolution mechanism in the Stir Zone was discussed.
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Effect of process parameters on Stir Zone microstructure in Ti–6Al–4V friction Stir welds
Journal of Materials Science, 2010Co-Authors: L. ZhouAbstract:The effects of the main process variables on the Stir Zone microstructure in friction Stir welds were investigated for Ti–6Al–4V. Welds were produced by employing varying welding speeds under a constant rotation speed or different rotation speeds at a constant welding speed. The Stir Zone microstructure was examined by optical microscopy and transmission electron microscopy. It was found that the Stir Zone microstructure was determined by the parameters controlling temperature and deformation history during the friction Stir welding. A bimodal microstructure characterized by primary α and transformed β with lamellar α + β or a full lamellar microstructure composed of basket-weave α + β lamellae could be developed in the Stir Zone. The microstructural evolution mechanism in the Stir Zone was discussed.
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the Stir Zone microstructure and its formation mechanism in ti 6al 4v friction Stir welds
Scripta Materialia, 2009Co-Authors: L. ZhouAbstract:The two-phase α + β titanium alloy, Ti–6Al–4V, was friction Stir welded using a W–Re pin tool, and defect-free welds were produced with proper welding parameters. A bimodal microstructure was formed in the Stir Zone due to dynamic recrystallization and phase transformation. Dynamic recrystallization was the main mechanism for microstructural refinement in the Stir Zone.
Hiroyuki Kokawa - One of the best experts on this subject based on the ideXlab platform.
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Mechanical Properties and Microstructure of Dissimilar Friction Stir Welds of 11Cr-Ferritic/Martensitic Steel to 316 Stainless Steel
Metallurgical and Materials Transactions A, 2015Co-Authors: Yutaka S Sato, Hiroyuki Kokawa, Hiromichi T. Fujii, Yasuhide Yano, Yoshihiro SekioAbstract:Dissimilar joints between ferritic and austenitic steels are of interest for selected applications in next generation fast reactors. In this study, dissimilar friction-Stir welding of an 11 pct Cr ferritic/martensitic steel to a 316 austenitic stainless steel was attempted and the mechanical properties and microstructure of the resulting welds were examined. Friction-Stir welding produces a Stir Zone without macroscopic weld-defects, but the two dissimilar steels are not intermixed. The two dissimilar steels are interleaved along a sharp zigzagging interface in the Stir Zone. During small-sized tensile testing of the Stir Zone, this sharp interface did not act as a fracture site. Furthermore, the microstructure of the Stir Zone was refined in both the ferritic/martensitic steel and the 316 stainless steel resulting in improved mechanical properties over the adjacent base material regions. This study demonstrates that friction-Stir welding can produce welds between dissimilar steels that contain no macroscopic weld-defects and display suitable mechanical properties.
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Grain structure and microtexture in friction Stir welded commercial purity titanium
Science and Technology of Welding and Joining, 2010Co-Authors: Y Zhang, Hiroyuki Kokawa, Yutaka S Sato, S H C Park, Satoshi HiranoAbstract:AbstractDefect free friction Stir welds were produced in commercial purity titanium at rotational speeds between 200 and 400 rev min–1. Friction Stir welding produced a finer grain structure in the Stir Zone than in the base material. Electron backscattered diffraction examination suggested that the fine grains in the Stir Zone were formed through both continuous and discontinuous recrystallisation during friction Stir welding. A torsion texture was observed in all welds and occupied most parts of the Stir Zone. Formation of this texture was attributed to the shear deformation along the tool shoulder during the Stirring process.
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Analysis of plastic flow of the Al alloy joint produced by friction Stir spot welding
Welding International, 2009Co-Authors: Shinji Koga, S. Yutaka Sato, Natsumi Abe, Hiroyuki KokawaAbstract:This study examined development of the Stir Zone and plastic flow of the material during friction Stir spot joining of aluminium alloys. The development of the Stir Zone was discussed through the observation of macro sections of the joints produced at various process times. The friction Stir spot joining trial with insert of Au foil to lap surface and the dissimilar lap friction Stir spot joining showed that the movement of the lap surface was attributed to the downward plastic flow from the upper plate to the lower plate around the probe. Additionally, it was clarified that the direction of the plastic flow was roughly the same as the direction of the tool rotation. The dissimilar butt friction Stir spot joining suggested that the plastic flow occurred not only within the Stir Zone but also in a larger area below the tool shoulder. The present study revealed that the threads on the probe surface were important for producing the plastic flow of thickness direction during friction Stir spot joining.
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Stir Zone microstructure of commercial purity titanium friction Stir welded using pcbn tool
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008Co-Authors: Y Zhang, Hiroyuki Kokawa, Yutaka S Sato, Seung Hwan C Park, Satoshi HiranoAbstract:Abstract In the present study, friction Stir welding was applied to commercial purity titanium using a polycrystalline cubic boron nitride tool, and microstructure and hardness in the weld were examined. Additionally, the microstructural evolution during friction Stir welding was also discussed. The Stir Zone consisted of fine equiaxed α grains surrounded by serrate grain boundaries, which were produced through the β → α allotropic transformation during the cooling cycle of friction Stir welding. The fine α grains caused higher hardness than that in the base material. A lath-shaped α grain structure containing Ti borides and tool debris was observed in the surface region of the Stir Zone, whose hardness was the highest in the weld.
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analysis of plastic flow of the al alloy lap joint produced by friction Stir spot welding
Quarterly Journal of The Japan Welding Society, 2008Co-Authors: Mitsuo Fujimoto, Shinji Koga, Natsumi Abe, Yutaka S Sato, Hiroyuki KokawaAbstract:This study examined development of the Stir Zone and plastic flow of the material during friction Stir spot joining of aluminum alloys. The development of the Stir Zone was discussed through the observation of macrosections of the joints produced at various process times. The friction Stir spot joining trial with insert of Au foil to lap surface and the dissimilar lap friction Stir spot joining showed that the movement of the lap surface was attributed to the downward plastic flow from the upper plate to the lower plate around the probe. Additionally, it was clarified that the direction of the plastic flow was roughly the same as the direction of the tool rotation. The dissimilar butt friction Stir spot joining suggested that the plastic flow occurred not only within the Stir Zone but also in larger area below the tool shoulder. The present study revealed that the threads on the probe surface were important for producing the plastic flow of thickness direction during friction Stir spot joining.
Hidetoshi Fujii - One of the best experts on this subject based on the ideXlab platform.
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Microstructure and mechanical properties of friction Stir welded duplex Mg–Li alloy LZ91
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2020Co-Authors: Mengran Zhou, Hidetoshi Fujii, Yoshiaki Morisada, Jian-yih WangAbstract:Abstract Superlight duplex Mg–Li alloy LZ91 with a thickness of 3 mm was successfully joined by friction Stir welding utilizing a tungsten carbide tool. The microstructures in the Stir Zone showed refined grains consisting of an equiaxed Mg-rich α phase and a Li-rich β phase. The grains in the Mg-rich α phase showed randomized crystal orientations after dynamic recrystallization. Due to the grain refinement and the random orientation of the Mg-rich α phase, the mechanical properties of the Stir Zone were optimized, and the hardness of the Stir Zones were higher than that of the base metal. At the same time, the heat affected Zone showed no decrease in its strength. Digital image correlation analyses revealed that the strain in the Stir Zone and base metal were respectively 0.05 and 0.6 before the samples fractured during the joint tensile tests. Therefore, the joints demonstrated 100% tensile efficiency compared with the base metal.
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laser assisted friction Stir processing of in738lc nickel based superalloy Stir Zone characteristics
Science and Technology of Welding and Joining, 2016Co-Authors: S M Mousavizade, Hidetoshi Fujii, M Pouranvari, F M Ghaini, Y D ChungAbstract:Friction Stir processing (FSP) of high softening-temperature materials such as nickel-based superalloys is considered to be difficult. Laser heating of a localised area ahead of the FSP tool was used to provide sufficient plasticity during the FSP of IN738LC nickel-based superalloy. The Stir Zone (SZ) microstructure of the friction Stir processed and laser-assisted friction Stir processed were characterised. Laser-assisted friction Stir processing (LAFSP) produced a defect-free pass, but FSP resulted in generation of a discontinuity in the SZ. Both lower volume fraction of partially dissolved γ′ precipitates and coarser grain structure of SZ in LAFSP led to more ductility of the SZ material and elimination of the defects.
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Microstructural Evolution of Body-Centred Cubic Fe-Al Alloy by Friction Stir Processing with SiC Particles Addition
Materials Science Forum, 2016Co-Authors: Toru Nagaoka, Hidetoshi Fujii, Yoshihisa Kimoto, Hiroyuki Watanabe, Masao Fukusumi, Yoshiaki Morisada, H. K. D. H. BhadeshiaAbstract:The surface of body-centred cubic Fe-7Al (mass%) alloy plate was successfully modified by friction Stir processing with SiC particles addition. The Stir Zone with SiC addition had an average grain size of 5.9 μm, smaller than that of 10.1 μm in the Stir Zone without SiC addition. SiC particles introduced by friction Stir processing were converted to fine Fe3AlCx particles by reaction with the ferrite matrix. The hardness near the surface of the Stir Zone was significantly increased to 351 HV by introduction of particles, compared to the hardness of 200 HV in the Stir Zone without particles addition. The dispersed particles also contributed to suppression of grain growth of the matrix at elevated temperature.
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Improved resistance to hydrogen embrittlement of friction Stir welded high carbon steel plates
International Journal of Hydrogen Energy, 2015Co-Authors: Hidetoshi FujiiAbstract:Abstract The hydrogen embrittlement of the friction Stir welded high carbon steel plates was evaluated by the cathodic hydrogen charging method. The welding was performed below Ac1 transformation point and therefore the Stir Zone of the welds contained refined ferrite matrix distributed with cementite particles. After hydrogen charging for 4 h, large quantities of irreversible dome-shaped blisters were formed on the surface of the base metal. However, no blisters were observed in the Stir Zone even after charging for 16 h. In addition, hydrogen-induced internal cracks were formed throughout the thickness of the base metal. But the development of the internal cracks in the base metal was restricted when getting close to the Stir Zone. The hydrogen charged Stir Zone showed less reduction of ductility than the base metal during tensile testing, which reveals that the friction Stir welded steel joints showed higher resistance to hydrogen embrittelment than base metal.
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Double-sided friction-Stir welding of magnesium alloy with concave–convex tools for texture control
Materials & Design, 2015Co-Authors: Juan Chen, Rintaro Ueji, Hidetoshi FujiiAbstract:Abstract Double-sided friction Stir welding (DFSW) with the combined use of convex and concave tools (concave-DFSW) was studied for the joining of a magnesium alloy. The sound joints made by the concave-DFSW were possible under the appropriate conditions, and the joints had a characteristic structure of the Stir Zone different from the conventional friction Stir welding with a one-sided tool rotation. The mean grain size of the Stir Zone decreased with the increasing rotation rate of the concave tool. This result indicated that the heat generation during the FSW is not only due to friction but also the plastic deformation. The complicated mixed metal flow that evolved by the convex tool randomized the texture in the Stir Zone, which provided the preferable tensile behavior.
Fucheng Zhang - One of the best experts on this subject based on the ideXlab platform.
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effect of welding heat input and post welding natural aging on hardness of Stir Zone for friction Stir welded 2024 t3 aluminum alloy thin sheet
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2013Co-Authors: Ruidong Fu, Jianfeng Zhang, Yijun Li, Ju Kang, Fucheng ZhangAbstract:The hardness of Stir Zone (SZ) at as-weld state and post-welding natural aging (PWNA) state under different heat input conditions were investigated for friction Stir-welded joints of 2024 aluminum alloy thin-sheets. Results show that welding heat input has obvious effect on the hardness of the SZ. Under the high welding heat input condition, the hardness of the SZ is lower than that of the base metal (BM). However, under low welding heat input condition, the hardness of the SZ exhibits strong dependency on the rotational speed of the Stirring tool. With increasing the rotational speed of the Stirring tool, the hardness of the SZ increases. The average hardness in the SZ of the joint welded at 1500 rpm and 1000 mm/min achieves the BM level. In comparison, the effect of the PWNA on the improvement of the hardness in the SZ is limited. The variation in the strengthening-phase particles plays a more important role than does grain size in the SZ for the improvement of hardness.
Yutaka S Sato - One of the best experts on this subject based on the ideXlab platform.
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Mechanical Properties and Microstructure of Dissimilar Friction Stir Welds of 11Cr-Ferritic/Martensitic Steel to 316 Stainless Steel
Metallurgical and Materials Transactions A, 2015Co-Authors: Yutaka S Sato, Hiroyuki Kokawa, Hiromichi T. Fujii, Yasuhide Yano, Yoshihiro SekioAbstract:Dissimilar joints between ferritic and austenitic steels are of interest for selected applications in next generation fast reactors. In this study, dissimilar friction-Stir welding of an 11 pct Cr ferritic/martensitic steel to a 316 austenitic stainless steel was attempted and the mechanical properties and microstructure of the resulting welds were examined. Friction-Stir welding produces a Stir Zone without macroscopic weld-defects, but the two dissimilar steels are not intermixed. The two dissimilar steels are interleaved along a sharp zigzagging interface in the Stir Zone. During small-sized tensile testing of the Stir Zone, this sharp interface did not act as a fracture site. Furthermore, the microstructure of the Stir Zone was refined in both the ferritic/martensitic steel and the 316 stainless steel resulting in improved mechanical properties over the adjacent base material regions. This study demonstrates that friction-Stir welding can produce welds between dissimilar steels that contain no macroscopic weld-defects and display suitable mechanical properties.
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Grain structure and microtexture in friction Stir welded commercial purity titanium
Science and Technology of Welding and Joining, 2010Co-Authors: Y Zhang, Hiroyuki Kokawa, Yutaka S Sato, S H C Park, Satoshi HiranoAbstract:AbstractDefect free friction Stir welds were produced in commercial purity titanium at rotational speeds between 200 and 400 rev min–1. Friction Stir welding produced a finer grain structure in the Stir Zone than in the base material. Electron backscattered diffraction examination suggested that the fine grains in the Stir Zone were formed through both continuous and discontinuous recrystallisation during friction Stir welding. A torsion texture was observed in all welds and occupied most parts of the Stir Zone. Formation of this texture was attributed to the shear deformation along the tool shoulder during the Stirring process.
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Stir Zone microstructure of commercial purity titanium friction Stir welded using pcbn tool
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008Co-Authors: Y Zhang, Hiroyuki Kokawa, Yutaka S Sato, Seung Hwan C Park, Satoshi HiranoAbstract:Abstract In the present study, friction Stir welding was applied to commercial purity titanium using a polycrystalline cubic boron nitride tool, and microstructure and hardness in the weld were examined. Additionally, the microstructural evolution during friction Stir welding was also discussed. The Stir Zone consisted of fine equiaxed α grains surrounded by serrate grain boundaries, which were produced through the β → α allotropic transformation during the cooling cycle of friction Stir welding. The fine α grains caused higher hardness than that in the base material. A lath-shaped α grain structure containing Ti borides and tool debris was observed in the surface region of the Stir Zone, whose hardness was the highest in the weld.
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analysis of plastic flow of the al alloy lap joint produced by friction Stir spot welding
Quarterly Journal of The Japan Welding Society, 2008Co-Authors: Mitsuo Fujimoto, Shinji Koga, Natsumi Abe, Yutaka S Sato, Hiroyuki KokawaAbstract:This study examined development of the Stir Zone and plastic flow of the material during friction Stir spot joining of aluminum alloys. The development of the Stir Zone was discussed through the observation of macrosections of the joints produced at various process times. The friction Stir spot joining trial with insert of Au foil to lap surface and the dissimilar lap friction Stir spot joining showed that the movement of the lap surface was attributed to the downward plastic flow from the upper plate to the lower plate around the probe. Additionally, it was clarified that the direction of the plastic flow was roughly the same as the direction of the tool rotation. The dissimilar butt friction Stir spot joining suggested that the plastic flow occurred not only within the Stir Zone but also in larger area below the tool shoulder. The present study revealed that the threads on the probe surface were important for producing the plastic flow of thickness direction during friction Stir spot joining.
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Grain growth phenomena in friction Stir welded 1100 Al during post-weld heat treatment
Science and Technology of Welding and Joining, 2007Co-Authors: Yutaka S Sato, H. Watanabe, Hiroyuki KokawaAbstract:AbstractGrain growth phenomena during post-weld heat treatment (PWHT) were examined in friction Stir (FS) welded 1100 Al. The FS welds were produced at rotational speeds between 550 and 3600 rev min−1. The FS weld produced at the lower rotational speed had the finer equiaxed grain structure containing feature of the more deformed microstructure in the as welded state. It was found that the regions having more deformed microstructure in the as welded state experienced abnormal grain growth more preferentially in the Stir Zone during PWHT. The Stir Zone exposed to higher temperature during FSW was more stable at higher PWHT temperatures. When the weld was heated for a long time at a temperature that was high enough for the abnormal grain growth, the Stir Zone produced at the lower rotational speed had the smaller grown grains. The present study suggested that the abnormal grain growth of the Stir Zone during PWHT had similar features of primary recrystallisation.
