The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform
Yutaka Koizumi - One of the best experts on this subject based on the ideXlab platform.
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Dislocation motion in the early stages of high temperature low stress creep in a single crystal superalloy with a small lattice misfit
Journal of Materials Science, 2010Co-Authors: Yutaka Koizumi, H Harada, Jingxiang Zhang, T KobayashiAbstract:Dislocation configurations at different creep stages (1100 °C and 137 MPa) in a superalloy TMS-75(+Ru) were studied in transmission electron microscopy (TEM) and the movement path of these creep-produced Dislocations could be fully illustrated. Due to the small value of γ/γ′ lattice misfit, these Dislocations cannot glide in the horizontal γ matrix channels by cross slip, but they mainly move by climbing around the γ′ cuboids. In the primary stage, the Dislocations first move by slip in the γ-matrix channels. When they reach the γ′ cuboids, they move by climbing along the γ′ cuboid surfaces. In the secondary creep stage, Dislocation reorientation in the (001) Interfacial planes happens slowly, away from the deposition orientation of 〈110〉 to the misfit orientation of 〈100〉. The velocity of the reorientation is lower and a perfect γ/γ′ Interfacial Dislocation network cannot be formed quickly. This factor results in a large creep rate of the alloy during the secondary creep stage. The path for Dislocation motion during the early creep stages consists of the following sequences: (i) climbing along the γ′ cuboid surface, (ii) deposition onto the (001) γ/γ′ Interfacial plane, and (iii) reorientation from the 〈110〉 direction to the 〈100〉 direction.
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the effect of lattice misfit on the Dislocation motion in superalloys during high temperature low stress creep
Acta Materialia, 2005Co-Authors: J X Zhang, Hiroshi Harada, Jincheng Wang, Yutaka KoizumiAbstract:Abstract The development of Dislocation configurations in two single-crystal superalloys during high-temperature low-stress creep (1100 °C, 137 MPa) was investigated with the use of transmission electron microscopy. Detailed analysis showed that the lattice misfit has an important influence on the Dislocation movement. For an alloy with a large negative lattice misfit, the Dislocations are able to move smoothly by cross-slip in the horizontal γ channels. During subsequent formation of γ/γ′ rafted structure, the Dislocations on the surface of γ′ cuboids rapidly re-orientate themselves from 〈1 1 0〉 to 〈1 0 0〉 direction and form a complete network. For an alloy with a small lattice misfit, the Dislocations move by the combination of climbing and gliding processes, and the resultant γ/γ′ Interfacial Dislocation network is incomplete. A good explanation of the creep curves is obtained from these differences in the microstructures.
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the influence of Interfacial Dislocation arrangements in a fourth generation single crystal tms 138 superalloy on creep properties
Journal of Materials Science, 2003Co-Authors: Jing Zhang, Yutaka Koizumi, T Murakumo, H HaradaAbstract:The morphologies of (001) γ/γ′ Interfacial Dislocation networks are studied through TEM observations. The lattice misfit has an important relation with creep property for superalloy during high temperature creep deformation. The fourth generation superalloy TMS-138 possesses superior creep properties based on its fine Interfacial Dislocation networks. The networks have two typical characteristics: closely spaced Dislocations and stable square morphology during creep deformation. Such arranged Dislocations can effectively prevent the slipping Dislocations in the γ phase from moving through the γ/γ′ interface and improve drastically the creep resistance in the fourth generation superalloy TMS-138.
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Dependence of creep strength on the Interfacial Dislocations in a fourth generation SC superalloy TMS-138
Scripta Materialia, 2003Co-Authors: Jun Zhang, T Murakumo, Hirofumi Harada, Yutaka KoizumiAbstract:Abstract There is an important relation between the γ/γ ′ Interfacial Dislocations and the minimum creep rate. During creep (1100 °C, 137 MPa), the finer the Interfacial Dislocation networks are, the smaller the minimum creep rate is. This is attributed to the interaction between the γ/γ ′ Interfacial Dislocations and slip Dislocations in the γ matrix.
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Interfacial Dislocation networks strengthening a fourth generation single crystal tms 138 superalloy
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2002Co-Authors: J X Zhang, Yutaka Koizumi, T Murakumo, Toshiharu Kobayashi, H Harada, S MasakiAbstract:The γ/γ′ Interfacial Dislocation networks in several creep-ruptured superalloys were analyzed. It was found that the morphologies of Dislocation networks differ slightly from each other in these alloys. The fourth-generation superalloy has finer Dislocation networks and keeps a relatively stable state. Comparatively, the Interfacial Dislocations in the third-generation superalloy show obvious curved features associated with possible climb or slip. These Interfacial Dislocation characteristics can be correlated with the creep behavior of these superalloys. The mechanisms of evolution of the Interfacial Dislocation networks were discussed.
H Harada - One of the best experts on this subject based on the ideXlab platform.
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Dislocation motion in the early stages of high temperature low stress creep in a single crystal superalloy with a small lattice misfit
Journal of Materials Science, 2010Co-Authors: Yutaka Koizumi, H Harada, Jingxiang Zhang, T KobayashiAbstract:Dislocation configurations at different creep stages (1100 °C and 137 MPa) in a superalloy TMS-75(+Ru) were studied in transmission electron microscopy (TEM) and the movement path of these creep-produced Dislocations could be fully illustrated. Due to the small value of γ/γ′ lattice misfit, these Dislocations cannot glide in the horizontal γ matrix channels by cross slip, but they mainly move by climbing around the γ′ cuboids. In the primary stage, the Dislocations first move by slip in the γ-matrix channels. When they reach the γ′ cuboids, they move by climbing along the γ′ cuboid surfaces. In the secondary creep stage, Dislocation reorientation in the (001) Interfacial planes happens slowly, away from the deposition orientation of 〈110〉 to the misfit orientation of 〈100〉. The velocity of the reorientation is lower and a perfect γ/γ′ Interfacial Dislocation network cannot be formed quickly. This factor results in a large creep rate of the alloy during the secondary creep stage. The path for Dislocation motion during the early creep stages consists of the following sequences: (i) climbing along the γ′ cuboid surface, (ii) deposition onto the (001) γ/γ′ Interfacial plane, and (iii) reorientation from the 〈110〉 direction to the 〈100〉 direction.
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deformation microstructures after low cycle fatigue in a fourth generation ni base sc superalloy tms 138
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2004Co-Authors: Hao Zhou, H Harada, Yasuhiro Aoki, Mikiya AraiAbstract:Abstract The deformation microstructures of a fourth-generation single-crystal (SC) Ni-base superalloy TMS-138 after low-cycle fatigue (LCF) have been studied. For comparison, a typical third-generation (TMS-75), and a second-generation (CMSX-4) Ni-base SC superalloy were also examined. The TMS-138 exhibited an excellent LCF behavior under a condition of R ratio of 0 at temperatures of 1073 K and 1173 K. The addition of refractory elements resulted in a remarkable improvement of LCF properties due to the different microstructure developed in TMS-138 as compared to the reference superalloys. The formation of a large number of stacking faults (SFs) in the matrix at 1073 K and the more completed rafts and smaller Interfacial Dislocation spacing at 1373 K were observed and discussed in relation to the performance of TMS-138 under a specific condition of R = 0. This work suggests that a fourth-generation SC superalloy TMS-138 is a promising candidate for applications in aeroengines.
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the influence of Interfacial Dislocation arrangements in a fourth generation single crystal tms 138 superalloy on creep properties
Journal of Materials Science, 2003Co-Authors: Jing Zhang, Yutaka Koizumi, T Murakumo, H HaradaAbstract:The morphologies of (001) γ/γ′ Interfacial Dislocation networks are studied through TEM observations. The lattice misfit has an important relation with creep property for superalloy during high temperature creep deformation. The fourth generation superalloy TMS-138 possesses superior creep properties based on its fine Interfacial Dislocation networks. The networks have two typical characteristics: closely spaced Dislocations and stable square morphology during creep deformation. Such arranged Dislocations can effectively prevent the slipping Dislocations in the γ phase from moving through the γ/γ′ interface and improve drastically the creep resistance in the fourth generation superalloy TMS-138.
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Interfacial Dislocation networks strengthening a fourth generation single crystal tms 138 superalloy
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2002Co-Authors: J X Zhang, Yutaka Koizumi, T Murakumo, Toshiharu Kobayashi, H Harada, S MasakiAbstract:The γ/γ′ Interfacial Dislocation networks in several creep-ruptured superalloys were analyzed. It was found that the morphologies of Dislocation networks differ slightly from each other in these alloys. The fourth-generation superalloy has finer Dislocation networks and keeps a relatively stable state. Comparatively, the Interfacial Dislocations in the third-generation superalloy show obvious curved features associated with possible climb or slip. These Interfacial Dislocation characteristics can be correlated with the creep behavior of these superalloys. The mechanisms of evolution of the Interfacial Dislocation networks were discussed.
Mikiya Arai - One of the best experts on this subject based on the ideXlab platform.
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deformation microstructures after low cycle fatigue in a fourth generation ni base sc superalloy tms 138
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2004Co-Authors: Hao Zhou, H Harada, Yasuhiro Aoki, Mikiya AraiAbstract:Abstract The deformation microstructures of a fourth-generation single-crystal (SC) Ni-base superalloy TMS-138 after low-cycle fatigue (LCF) have been studied. For comparison, a typical third-generation (TMS-75), and a second-generation (CMSX-4) Ni-base SC superalloy were also examined. The TMS-138 exhibited an excellent LCF behavior under a condition of R ratio of 0 at temperatures of 1073 K and 1173 K. The addition of refractory elements resulted in a remarkable improvement of LCF properties due to the different microstructure developed in TMS-138 as compared to the reference superalloys. The formation of a large number of stacking faults (SFs) in the matrix at 1073 K and the more completed rafts and smaller Interfacial Dislocation spacing at 1373 K were observed and discussed in relation to the performance of TMS-138 under a specific condition of R = 0. This work suggests that a fourth-generation SC superalloy TMS-138 is a promising candidate for applications in aeroengines.
T Murakumo - One of the best experts on this subject based on the ideXlab platform.
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the influence of Interfacial Dislocation arrangements in a fourth generation single crystal tms 138 superalloy on creep properties
Journal of Materials Science, 2003Co-Authors: Jing Zhang, Yutaka Koizumi, T Murakumo, H HaradaAbstract:The morphologies of (001) γ/γ′ Interfacial Dislocation networks are studied through TEM observations. The lattice misfit has an important relation with creep property for superalloy during high temperature creep deformation. The fourth generation superalloy TMS-138 possesses superior creep properties based on its fine Interfacial Dislocation networks. The networks have two typical characteristics: closely spaced Dislocations and stable square morphology during creep deformation. Such arranged Dislocations can effectively prevent the slipping Dislocations in the γ phase from moving through the γ/γ′ interface and improve drastically the creep resistance in the fourth generation superalloy TMS-138.
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Dependence of creep strength on the Interfacial Dislocations in a fourth generation SC superalloy TMS-138
Scripta Materialia, 2003Co-Authors: Jun Zhang, T Murakumo, Hirofumi Harada, Yutaka KoizumiAbstract:Abstract There is an important relation between the γ/γ ′ Interfacial Dislocations and the minimum creep rate. During creep (1100 °C, 137 MPa), the finer the Interfacial Dislocation networks are, the smaller the minimum creep rate is. This is attributed to the interaction between the γ/γ ′ Interfacial Dislocations and slip Dislocations in the γ matrix.
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Interfacial Dislocation networks strengthening a fourth generation single crystal tms 138 superalloy
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2002Co-Authors: J X Zhang, Yutaka Koizumi, T Murakumo, Toshiharu Kobayashi, H Harada, S MasakiAbstract:The γ/γ′ Interfacial Dislocation networks in several creep-ruptured superalloys were analyzed. It was found that the morphologies of Dislocation networks differ slightly from each other in these alloys. The fourth-generation superalloy has finer Dislocation networks and keeps a relatively stable state. Comparatively, the Interfacial Dislocations in the third-generation superalloy show obvious curved features associated with possible climb or slip. These Interfacial Dislocation characteristics can be correlated with the creep behavior of these superalloys. The mechanisms of evolution of the Interfacial Dislocation networks were discussed.
T.g. Nieh - One of the best experts on this subject based on the ideXlab platform.
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Creep deformation of fully lamellar TiAl controlled by the viscous glide of Interfacial Dislocations
Intermetallics, 1999Co-Authors: L.m. Hsiung, T.g. NiehAbstract:Abstract Creep mechanisms of fully lamellar TiAl with a refined microstructure ( γ lamellae: 100–300 nm thick, α 2 lamellae: 10–50 nm thick) have been investigated. A nearly linear creep behavior (i.e. the steady-state creep rate is nearly proportional to the applied stress) was observed when the alloy was creep deformed at low applied stresses ( γ and α 2 lamellae are very limited in a low stress level as a result of the refined lamellar microstructure, creep mechanisms based upon glide and/or climb of lattice Dislocations become insignificant. Instead, the motion of Interfacial Dislocation arrays on γ / α 2 and γ / γ interfaces (i.e. interface sliding) has found to be a predominant deformation mechanism. According to the observed Interfacial substructure caused by interface sliding and the measured activation energy for creep, it is proposed that creep deformation of the refined lamellar TiAl in the intermediate-temperature and low-stress regime is primarily controlled by the viscous glide of Interfacial Dislocations.
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Formation of deformation twins in a crept lamellar TiAl alloy
Scripta Materialia, 1998Co-Authors: J.g. Wang, L.m. Hsiung, T.g. NiehAbstract:The substructures of a lamellar TiAl alloy deformed at 760 C with a low applied stress to a large strain (138 MPa, 1.5%), and a high applied stress to a small strain (518 MPa, 0.67%) were examined. During creep, Interfacial gliding Dislocations are initially retarded by either intrinsic barriers (e.g., ledges in the surface) or extrinsic barriers (i.e., the reaction of lattice Dislocation with interface), resulting in a Dislocation pile-up configuration. With further deformation, deformation twins are formed, and Dislocation emission from interfaces also occurs. A critical local stress is required to initiate deformation twins which are suggested to be formed via a stair-rod cross-slip mechanism. This critical stress can be fulfilled by an Interfacial Dislocation pile-up.