The Experts below are selected from a list of 4017 Experts worldwide ranked by ideXlab platform
Stewart W Williams - One of the best experts on this subject based on the ideXlab platform.
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crack path selection at the interface of Wrought and wire arc additive manufactured ti 6al 4v
Materials & Design, 2016Co-Authors: Jikui Zhang, Xiang Zhang, Xueyuan Wang, Jialuo Ding, Yeli Traore, Sanjooram Paddea, Stewart W WilliamsAbstract:Crack propagation deviation tendency in specimens containing an interface between Wrought Alloy substrate and Wire + Arc Additive Manufacture (WAAM) built Ti–6Al–4V is investigated from the viewpoints of microstructure, residual stress and bi-material system. It is found that a crack initiated at the interface tends to grow into the substrate that has equiaxed microstructure and lower resistance to fatigue crack propagation. Experimental observations are interpreted by finite element modelling of the effects of residual stress and mechanical property mismatch between the WAAM and Wrought Alloy. Residual stresses retained in the compact tension specimens are evaluated based on measured residual stress in the initial WAAM built wall. Cracks perpendicular to the interface kept a straight path owing to the symmetrical residual stress distribution. In this case the tangential stress in bi-material model is also symmetric and has the maximum value at the initial crack plane. In contrast, cracks parallel to the interface are inclined to grow towards the substrate due to the mode II (or sliding mode) stress intensity factor caused by the asymmetric residual stress field. Asymmetric tangential stress in the bi-material model also contributes to the observed crack deviation trend according to the maximum tangential stress criterion.
Xiang Zhang - One of the best experts on this subject based on the ideXlab platform.
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crack path selection at the interface of Wrought and wire arc additive manufactured ti 6al 4v
Materials & Design, 2016Co-Authors: Jikui Zhang, Xiang Zhang, Xueyuan Wang, Jialuo Ding, Yeli Traore, Sanjooram Paddea, Stewart W WilliamsAbstract:Crack propagation deviation tendency in specimens containing an interface between Wrought Alloy substrate and Wire + Arc Additive Manufacture (WAAM) built Ti–6Al–4V is investigated from the viewpoints of microstructure, residual stress and bi-material system. It is found that a crack initiated at the interface tends to grow into the substrate that has equiaxed microstructure and lower resistance to fatigue crack propagation. Experimental observations are interpreted by finite element modelling of the effects of residual stress and mechanical property mismatch between the WAAM and Wrought Alloy. Residual stresses retained in the compact tension specimens are evaluated based on measured residual stress in the initial WAAM built wall. Cracks perpendicular to the interface kept a straight path owing to the symmetrical residual stress distribution. In this case the tangential stress in bi-material model is also symmetric and has the maximum value at the initial crack plane. In contrast, cracks parallel to the interface are inclined to grow towards the substrate due to the mode II (or sliding mode) stress intensity factor caused by the asymmetric residual stress field. Asymmetric tangential stress in the bi-material model also contributes to the observed crack deviation trend according to the maximum tangential stress criterion.
Xueyuan Wang - One of the best experts on this subject based on the ideXlab platform.
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crack path selection at the interface of Wrought and wire arc additive manufactured ti 6al 4v
Materials & Design, 2016Co-Authors: Jikui Zhang, Xiang Zhang, Xueyuan Wang, Jialuo Ding, Yeli Traore, Sanjooram Paddea, Stewart W WilliamsAbstract:Crack propagation deviation tendency in specimens containing an interface between Wrought Alloy substrate and Wire + Arc Additive Manufacture (WAAM) built Ti–6Al–4V is investigated from the viewpoints of microstructure, residual stress and bi-material system. It is found that a crack initiated at the interface tends to grow into the substrate that has equiaxed microstructure and lower resistance to fatigue crack propagation. Experimental observations are interpreted by finite element modelling of the effects of residual stress and mechanical property mismatch between the WAAM and Wrought Alloy. Residual stresses retained in the compact tension specimens are evaluated based on measured residual stress in the initial WAAM built wall. Cracks perpendicular to the interface kept a straight path owing to the symmetrical residual stress distribution. In this case the tangential stress in bi-material model is also symmetric and has the maximum value at the initial crack plane. In contrast, cracks parallel to the interface are inclined to grow towards the substrate due to the mode II (or sliding mode) stress intensity factor caused by the asymmetric residual stress field. Asymmetric tangential stress in the bi-material model also contributes to the observed crack deviation trend according to the maximum tangential stress criterion.
Shae K. Kim - One of the best experts on this subject based on the ideXlab platform.
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Thixoextrusion for 7075 Al Wrought Alloy Tube
Solid State Phenomena, 2008Co-Authors: Dong In Jang, Young Ok Yoon, Shae K. KimAbstract:The aim of this study was to improve extrudability limit, eliminate welding line and obtain optimum thixoextrusion conditions for manufacturing tubes of 7075 Al Wrought Alloy. By thixoextrusion, it was possible to improve deformability, control isotropy with extrusion direction, eliminate welding line (seamless) and save cost due to low energy consumption compared with conventional extrusion processes. The welded part was not observed at the welding line area. The grains of thixoextruded tube were homogeneously distributed and equiaxed grains were observed. Therefore, thixoextrusion is the most effective variable for the control of the magnitude of the welding line.
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Influence of Thixoextrusion Parameters on Mechanical Properties of Thixoextruded 7075 Al Wrought Alloy
Solid State Phenomena, 2007Co-Authors: Young Ok Yoon, Shae K. KimAbstract:The main emphasis of this study is to utilize thixoextrusion process for improving extrudability of 7075 Al Wrought Alloy. In the present study, the influences of thixoextrusion parameters, such as initial ram speed and die bearing length, on mechanical properties of thixoextruded 7075 Al Wrought Alloy were investigated. The results of thixoextrusion experiments about microstructures and mechanical properties were compared with conventional extrusion results. The maximum extrusion pressure of thixoextrusion processes was seven times lower than that of conventional hot extrusion processes. The hot extruded bars show a large amount of grains which are stretched along the extrusion direction and asymmetry of grains was formed to extrusion direction, while the microstructures of the thixoextruded bar did not show any asymmetry and grains were homogeneously distributed. The hardness values of thixoextruded bar were higher than that of conventional hot extruded bar.
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Effect of Partial Remelting Procedure on the Microstructural Evolution of 7075 Al Wrought Alloy for Thixoextrusion
Solid State Phenomena, 2006Co-Authors: Young Ok Yoon, Jin-kyu Lee, Shae K. KimAbstract:The feasibility study for thixoextrusion of 7075 Al Wrought Alloys was carried out with respect to reheating profile, isothermal holding temperature and time during the partial remelting through simple partial remelting. The reheating rates were 40/min and 60/min. The isothermal holding temperatures were controlled at 609, 622, 628 and 632 for 0, 2, 5, 10 and 30 min. The interesting point of this study was that the thixotropic structures of 7075 Al Wrought Alloy without additional pretreatment could be obtained through simple partial remelting. The average grain size was significantly smaller in the quickly heated specimen. The liquid fraction was increased with increasing isothermal holding temperature and time while the average grain size was inversely proportional to isothermal holding temperature and time. However, there was no big change of liquid fraction and average grain size with respect to isothermal holding time. The important fact that the liquid fraction and average grain size were almost uniform after 5 min is considered very useful for thixoextrusion in terms of actual extrusion time.
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Development of Thixoextrusion Process for 7000 Series Al Wrought Alloys
Solid State Phenomena, 2006Co-Authors: Young Ok Yoon, Jin-kyu Lee, Dong In Jang, Shae K. KimAbstract:Thixoextrusion for 7003 and 7075 Al Wrought Alloys with different content of Cu was carried out with respect to isothermal holding temperature in the partially remelted semisolid state. Especially, despite higher extrudability index of 7075 Al Wrought Alloy compared with the extrudability index of 7003 Al Wrought Alloy, the maximum extrusion pressures of 7075 Al Wrought Alloy were about the same as the maximum extrusion pressures of 7003 Al Wrought Alloy at temperature with the liquid fraction 10% (7003-624, 7075-609). The hardness values of thixoextruded specimens were higher than that of as-quenched specimens only after partial remelting. The microstructures of thixoextruded specimens did not show any dendrites or rosette-like structures. The average grain sizes of thixoextruded specimens were smaller than average grain sizes of homogenized specimens.
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Microstructural Control of 7075 Al Wrought Alloys through Thixoextrusion Route
Materials Science Forum, 2006Co-Authors: Young Ok Yoon, Jin-kyu Lee, Dong In Jang, Shae K. KimAbstract:Thixoextrusion, one of the thixoforming processes, has advantages of high productivity, reduction of the extrusion pressure, extension of the die life, and cost saving owing to its low energy consumption compared with the conventional extrusion processes. Especially, thixoextrusion process is expected to be very effective for hard-to-form materials with high strength. The present study focuses on 7075 Al Wrought Alloy to investigate the potential industrial applications of the thixoextrusion process. The microstructural evolution of 7075 Al Wrought Alloy for thixoextrusion was investigated with respect to isothermal holding temperature and time in the partially remelted semisolid state. The results showed that the liquid fraction increased with increasing isothermal holding temperature and time while the average grain size was inversely proportional to isothermal holding temperature and time up to 5min. However, there was no big change of liquid fraction and average grain size with respect to isothermal holding temperature and time. The important fact that the liquid fraction and average grain size were almost uniform after 5 min holding time is considered very useful for thixoextrusion in terms of process control.
Young Ok Yoon - One of the best experts on this subject based on the ideXlab platform.
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Thixoextrusion for 7075 Al Wrought Alloy Tube
Solid State Phenomena, 2008Co-Authors: Dong In Jang, Young Ok Yoon, Shae K. KimAbstract:The aim of this study was to improve extrudability limit, eliminate welding line and obtain optimum thixoextrusion conditions for manufacturing tubes of 7075 Al Wrought Alloy. By thixoextrusion, it was possible to improve deformability, control isotropy with extrusion direction, eliminate welding line (seamless) and save cost due to low energy consumption compared with conventional extrusion processes. The welded part was not observed at the welding line area. The grains of thixoextruded tube were homogeneously distributed and equiaxed grains were observed. Therefore, thixoextrusion is the most effective variable for the control of the magnitude of the welding line.
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Influence of Thixoextrusion Parameters on Mechanical Properties of Thixoextruded 7075 Al Wrought Alloy
Solid State Phenomena, 2007Co-Authors: Young Ok Yoon, Shae K. KimAbstract:The main emphasis of this study is to utilize thixoextrusion process for improving extrudability of 7075 Al Wrought Alloy. In the present study, the influences of thixoextrusion parameters, such as initial ram speed and die bearing length, on mechanical properties of thixoextruded 7075 Al Wrought Alloy were investigated. The results of thixoextrusion experiments about microstructures and mechanical properties were compared with conventional extrusion results. The maximum extrusion pressure of thixoextrusion processes was seven times lower than that of conventional hot extrusion processes. The hot extruded bars show a large amount of grains which are stretched along the extrusion direction and asymmetry of grains was formed to extrusion direction, while the microstructures of the thixoextruded bar did not show any asymmetry and grains were homogeneously distributed. The hardness values of thixoextruded bar were higher than that of conventional hot extruded bar.
-
Effect of Partial Remelting Procedure on the Microstructural Evolution of 7075 Al Wrought Alloy for Thixoextrusion
Solid State Phenomena, 2006Co-Authors: Young Ok Yoon, Jin-kyu Lee, Shae K. KimAbstract:The feasibility study for thixoextrusion of 7075 Al Wrought Alloys was carried out with respect to reheating profile, isothermal holding temperature and time during the partial remelting through simple partial remelting. The reheating rates were 40/min and 60/min. The isothermal holding temperatures were controlled at 609, 622, 628 and 632 for 0, 2, 5, 10 and 30 min. The interesting point of this study was that the thixotropic structures of 7075 Al Wrought Alloy without additional pretreatment could be obtained through simple partial remelting. The average grain size was significantly smaller in the quickly heated specimen. The liquid fraction was increased with increasing isothermal holding temperature and time while the average grain size was inversely proportional to isothermal holding temperature and time. However, there was no big change of liquid fraction and average grain size with respect to isothermal holding time. The important fact that the liquid fraction and average grain size were almost uniform after 5 min is considered very useful for thixoextrusion in terms of actual extrusion time.
-
Development of Thixoextrusion Process for 7000 Series Al Wrought Alloys
Solid State Phenomena, 2006Co-Authors: Young Ok Yoon, Jin-kyu Lee, Dong In Jang, Shae K. KimAbstract:Thixoextrusion for 7003 and 7075 Al Wrought Alloys with different content of Cu was carried out with respect to isothermal holding temperature in the partially remelted semisolid state. Especially, despite higher extrudability index of 7075 Al Wrought Alloy compared with the extrudability index of 7003 Al Wrought Alloy, the maximum extrusion pressures of 7075 Al Wrought Alloy were about the same as the maximum extrusion pressures of 7003 Al Wrought Alloy at temperature with the liquid fraction 10% (7003-624, 7075-609). The hardness values of thixoextruded specimens were higher than that of as-quenched specimens only after partial remelting. The microstructures of thixoextruded specimens did not show any dendrites or rosette-like structures. The average grain sizes of thixoextruded specimens were smaller than average grain sizes of homogenized specimens.
-
Microstructural Control of 7075 Al Wrought Alloys through Thixoextrusion Route
Materials Science Forum, 2006Co-Authors: Young Ok Yoon, Jin-kyu Lee, Dong In Jang, Shae K. KimAbstract:Thixoextrusion, one of the thixoforming processes, has advantages of high productivity, reduction of the extrusion pressure, extension of the die life, and cost saving owing to its low energy consumption compared with the conventional extrusion processes. Especially, thixoextrusion process is expected to be very effective for hard-to-form materials with high strength. The present study focuses on 7075 Al Wrought Alloy to investigate the potential industrial applications of the thixoextrusion process. The microstructural evolution of 7075 Al Wrought Alloy for thixoextrusion was investigated with respect to isothermal holding temperature and time in the partially remelted semisolid state. The results showed that the liquid fraction increased with increasing isothermal holding temperature and time while the average grain size was inversely proportional to isothermal holding temperature and time up to 5min. However, there was no big change of liquid fraction and average grain size with respect to isothermal holding temperature and time. The important fact that the liquid fraction and average grain size were almost uniform after 5 min holding time is considered very useful for thixoextrusion in terms of process control.
