The Experts below are selected from a list of 3168 Experts worldwide ranked by ideXlab platform
Tian Sugui - One of the best experts on this subject based on the ideXlab platform.
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Creep properties and effect factors of hot continuous rolled Ti–6Al–4V alloy
Materials Science and Engineering: A, 2011Co-Authors: Tian Sugui, Bao Xianyu, Chen LiqingAbstract:Abstract By means of heat treatment, measurement of Creep properties and contract analysis of dislocations configuration, Creep behaviors and effect factors of hot continuous rolled (HCR) Ti–6Al–4V alloy are investigated. Results show that, the microstructure of HCR alloy after solution treatment at temperature lower than β phase transus point consists of the super-saturation equiaxial α phase and “basket weave” structure. The quantity of “basket weave” structure increases with solution temperature, and the fully “basket weave” structure may be obtained after solution treatment at 1000 °C. Compared to the alloy solution treated at 940 °C, the alloy treated at 1000 °C has lower strain rate and longer Creep Lifetime under the conditions of applied stress of 575 MPa at 420 °C. In the range of the applied stress and temperature, the Creep activation energy of the alloy is calculated to be Q a = 249.8 kJ/mol. Deformation mechanism of HCR alloy during Creep is double orientations slips of dislocations activated within α phase with HCP structure, while deformation feature of the alloy solution treated at 940 °C is the wave-like 〈a + c〉 dislocations activated on the pyramidal planes in the α phase. Solution treated at 1000 °C, deformation mechanism of the alloy is that the multiple slips of (1/2)〈1 1 1〉 dislocations are activated within β phase with BCC structure, in which V-rich β phase with high volume fraction may enhance Creep resistance, which is thought to be the main reason of the alloy possessing the low strain rate and longer Creep Lifetime.
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influence of tcp phase and its morphology on Creep properties of single crystal nickel based superalloys
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2010Co-Authors: Tian Sugui, Wang Minggang, Li Tang, Qian BenjiangAbstract:Abstract By means of the measurement of Creep curves and SEM, TEM observation, an investigation has been made into the influences of the element Re and TCP phase on the Creep properties of the single crystal nickel-based superalloys. Results show that, during aging of the containing/free Re superalloys, the slice-like TCP phase identified as μ phase is precipitated along the 〈1 1 0〉 orientation on {1 1 1} planes. As the aging time prolongs, the quantities of the slice-like μ phase precipitated in the alloys increase, no spheroidized feature of μ phase is detected in 6%W alloy, but the slice-like μ phase in 4.5%Re alloy is transformed into the sphere-like morphology. During aging, the evolution process of the strip-like μ phase consists of the inhomogeneous coarsening, the appearance of the groove and the decomposition of the one in the interval distance. The higher chemical potential in the strip-like μ phase with the groove acts as the driving force for promoting the diffusion of the solute atoms, which results in the strip-like μ phase dissolved and the groove deepened up to separation to form the sphere-like morphology. During Creep, the stress concentration generates easily in the regions near the strip-like μ phase, and promotes the initiation and propagation of the cracks, which is the main reason of reducing the Creep Lifetime of 6%W alloy to a great extent, but the stress concentration does not easily generate in the regions near the sphere-like μ phase, this is the main reason of reducing the Creep Lifetime of 4.5%Re alloy to a small extent.
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influence of tcp phase and its morphology on Creep properties of single crystal nickel based superalloys
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2010Co-Authors: Tian Sugui, Wang Minggang, Li Tang, Qian Benjiang, Xie JunAbstract:Abstract By means of the measurement of Creep curves and SEM, TEM observation, an investigation has been made into the influences of the element Re and TCP phase on the Creep properties of the single crystal nickel-based superalloys. Results show that, during aging of the containing/free Re superalloys, the slice-like TCP phase identified as μ phase is precipitated along the 〈1 1 0〉 orientation on {1 1 1} planes. As the aging time prolongs, the quantities of the slice-like μ phase precipitated in the alloys increase, no spheroidized feature of μ phase is detected in 6%W alloy, but the slice-like μ phase in 4.5%Re alloy is transformed into the sphere-like morphology. During aging, the evolution process of the strip-like μ phase consists of the inhomogeneous coarsening, the appearance of the groove and the decomposition of the one in the interval distance. The higher chemical potential in the strip-like μ phase with the groove acts as the driving force for promoting the diffusion of the solute atoms, which results in the strip-like μ phase dissolved and the groove deepened up to separation to form the sphere-like morphology. During Creep, the stress concentration generates easily in the regions near the strip-like μ phase, and promotes the initiation and propagation of the cracks, which is the main reason of reducing the Creep Lifetime of 6%W alloy to a great extent, but the stress concentration does not easily generate in the regions near the sphere-like μ phase, this is the main reason of reducing the Creep Lifetime of 4.5%Re alloy to a small extent.
Qian Benjiang - One of the best experts on this subject based on the ideXlab platform.
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influence of tcp phase and its morphology on Creep properties of single crystal nickel based superalloys
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2010Co-Authors: Tian Sugui, Wang Minggang, Li Tang, Qian BenjiangAbstract:Abstract By means of the measurement of Creep curves and SEM, TEM observation, an investigation has been made into the influences of the element Re and TCP phase on the Creep properties of the single crystal nickel-based superalloys. Results show that, during aging of the containing/free Re superalloys, the slice-like TCP phase identified as μ phase is precipitated along the 〈1 1 0〉 orientation on {1 1 1} planes. As the aging time prolongs, the quantities of the slice-like μ phase precipitated in the alloys increase, no spheroidized feature of μ phase is detected in 6%W alloy, but the slice-like μ phase in 4.5%Re alloy is transformed into the sphere-like morphology. During aging, the evolution process of the strip-like μ phase consists of the inhomogeneous coarsening, the appearance of the groove and the decomposition of the one in the interval distance. The higher chemical potential in the strip-like μ phase with the groove acts as the driving force for promoting the diffusion of the solute atoms, which results in the strip-like μ phase dissolved and the groove deepened up to separation to form the sphere-like morphology. During Creep, the stress concentration generates easily in the regions near the strip-like μ phase, and promotes the initiation and propagation of the cracks, which is the main reason of reducing the Creep Lifetime of 6%W alloy to a great extent, but the stress concentration does not easily generate in the regions near the sphere-like μ phase, this is the main reason of reducing the Creep Lifetime of 4.5%Re alloy to a small extent.
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influence of tcp phase and its morphology on Creep properties of single crystal nickel based superalloys
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2010Co-Authors: Tian Sugui, Wang Minggang, Li Tang, Qian Benjiang, Xie JunAbstract:Abstract By means of the measurement of Creep curves and SEM, TEM observation, an investigation has been made into the influences of the element Re and TCP phase on the Creep properties of the single crystal nickel-based superalloys. Results show that, during aging of the containing/free Re superalloys, the slice-like TCP phase identified as μ phase is precipitated along the 〈1 1 0〉 orientation on {1 1 1} planes. As the aging time prolongs, the quantities of the slice-like μ phase precipitated in the alloys increase, no spheroidized feature of μ phase is detected in 6%W alloy, but the slice-like μ phase in 4.5%Re alloy is transformed into the sphere-like morphology. During aging, the evolution process of the strip-like μ phase consists of the inhomogeneous coarsening, the appearance of the groove and the decomposition of the one in the interval distance. The higher chemical potential in the strip-like μ phase with the groove acts as the driving force for promoting the diffusion of the solute atoms, which results in the strip-like μ phase dissolved and the groove deepened up to separation to form the sphere-like morphology. During Creep, the stress concentration generates easily in the regions near the strip-like μ phase, and promotes the initiation and propagation of the cracks, which is the main reason of reducing the Creep Lifetime of 6%W alloy to a great extent, but the stress concentration does not easily generate in the regions near the sphere-like μ phase, this is the main reason of reducing the Creep Lifetime of 4.5%Re alloy to a small extent.
Hiromichi Hongo - One of the best experts on this subject based on the ideXlab platform.
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Creep Lifetime and microstructure evolution in boron added 9cr 1mo heat resistant steel
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2019Co-Authors: Tetsuya Matsunaga, Hiromichi Hongo, Masaaki Tabuchi, Maaouia Souissi, Ryoji Sahara, Collin Whitt, Wei Zhang, Michael J. MillsAbstract:Abstract The relationship between Creep Lifetime and microstructure, especially precipitate morphology, of a new 9Cr heat-resistant steel containing 0.011 wt% boron was examined. The B-added steel showed superior Creep Lifetime compared to conventional Gr. 91 steel due to the microstructural stability of the new steel at 873 K. The new steel also exhibited prior-austenite grain boundaries with a high coverage of precipitates, which increased from ~30% to ~40% during Creep tests, whereas that of the conventional Gr. 91 steel was nearly stable, at ~25%. In addition, the B-containing M23C6 in the B-added steel had a lower coherency, i.e., a higher interface energy, between the precipitate and the matrix when compared to conventional Gr, 91 steel. These factors led to a higher pinning pressure to resist interface migration in the B-added steel. Microscopy revealed that chemical stabilization had a significant effect on the coarsening behavior of M23C6. Chemical analyses revealed that M23C6 became Cr-rich during the early stages of Creep, in which rapid coarsening was observed at a rate contrast of >1.0 × 10−28 m3/s; in this state, M23C6 was approaching equilibrium Cr concentration. In later stages of Creep, moderate coarsening occurred with a rate constant of ~8.1 × 10−30 m3/s; in this state, chemical stability was achieved but diffusion and dissolution of small precipitates were dominant.
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Creep Lifetime and microstructure evolution in boron-added 9Cr–1Mo heat-resistant steel
Materials Science and Engineering: A, 2019Co-Authors: Tetsuya Matsunaga, Hiromichi Hongo, Masaaki Tabuchi, Maaouia Souissi, Ryoji Sahara, Collin Whitt, Wei Zhang, Michael J. MillsAbstract:Abstract The relationship between Creep Lifetime and microstructure, especially precipitate morphology, of a new 9Cr heat-resistant steel containing 0.011 wt% boron was examined. The B-added steel showed superior Creep Lifetime compared to conventional Gr. 91 steel due to the microstructural stability of the new steel at 873 K. The new steel also exhibited prior-austenite grain boundaries with a high coverage of precipitates, which increased from ~30% to ~40% during Creep tests, whereas that of the conventional Gr. 91 steel was nearly stable, at ~25%. In addition, the B-containing M23C6 in the B-added steel had a lower coherency, i.e., a higher interface energy, between the precipitate and the matrix when compared to conventional Gr, 91 steel. These factors led to a higher pinning pressure to resist interface migration in the B-added steel. Microscopy revealed that chemical stabilization had a significant effect on the coarsening behavior of M23C6. Chemical analyses revealed that M23C6 became Cr-rich during the early stages of Creep, in which rapid coarsening was observed at a rate contrast of >1.0 × 10−28 m3/s; in this state, M23C6 was approaching equilibrium Cr concentration. In later stages of Creep, moderate coarsening occurred with a rate constant of ~8.1 × 10−30 m3/s; in this state, chemical stability was achieved but diffusion and dissolution of small precipitates were dominant.
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Creep Property of Boron Added 9Cr Heat Resistant Steels after Welding
Materials Science Forum, 2018Co-Authors: Tetsuya Matsunaga, Hiromichi Hongo, Masaaki Tabuchi, Maaouia Souissi, Ryoji Sahara, Wei Zhang, Michael J. MillsAbstract:Although welding results in premature failure by type IV fracture under high temperature Creep conditions, the alloy design of light elements such as boron addition and nitrogen reduction enhances the Creep Lifetime of 9Cr heat resistant steel. In particular, the simulated heat affected zone (SHAZ) sample of new 9Cr steel (called TA steel) shows about 10 times longer Creep Lifetime than that of the standard Gr. 91 steel. The welded TA steel is thus expected to exhibit good Creep properties because its SHAZ sample has coarser grains and suppresses type IV fracture. The preservation of base metal’s microstructure after welding results from the precipitate morphology, such as high grain boundary coverage by precipitates and low amount of MX being nucleation sites of ferrite grains during the a-g phase transformation. In addition, the increase of stability of M23C6 affects high pinning pressure toward grain boundary migration upon rapid heating during welding. First-principles calculations confirm the increased stability when boron is absorbed by M23C6. Moreover, the calculations reveals that boron decreases the coherency between matrix and M23C6, suppressing grain coarsening during Creep tests in TA steel. It is concluded that the increased microstructural stability during welding and long high temperature exposure generates the elongated Creep Lifetime in welded TA steel including about 0.01 wt% boron and less than 0.01 wt% nitrogen.
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Suppression of grain refinement in heat-affected zone of 9Cr–3W–3Co–VNb steels
Materials Science and Engineering: A, 2016Co-Authors: Tetsuya Matsunaga, Hiromichi Hongo, Masaaki Tabuchi, Ryoji SaharaAbstract:Abstract Prompt phase transformations make grains in the heat-affected zone (HAZ) smaller during welding of 9% chromium (9Cr) heat-resistant steels leading to premature failure under Creep conditions, which is well known as a type IV fracture. Because the type IV fracture shortens the Creep Lifetime of the steels, suppressing the fracture is an urgent task in the energy industry. The present study shows that boron addition and nitrogen reduction inhibit grain refinement after welding because of a change in the morphology of the precipitate at prior austenite grain boundaries. In conventional 9Cr steel (ASME Gr. 92 steel), a high amount of MX was unable to pin interface migration of the phase transformation and generated fine grains in the HAZ. In the new B-added steels, B-stabilized M 23 C 6 became the dominant precipitate and showed a larger pinning effect of the phase transformation than MX, which resulted in coarse grains in the HAZ. This suggests that designing stabilized M 23 C 6 forms a superior welded microstructure and results in a longer Creep Lifetime of 9Cr steels.
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prediction of Creep Lifetime for butt welded joint of type 304 stainless steel by finite element method incorporating damage variable
Quarterly Journal of The Japan Welding Society, 1995Co-Authors: Junichi Kinugawa, Hiromichi Hongo, Masayoshi Yamazaki, Takashi Watanabe, Yoshio MonmaAbstract:A computational method of predicting Creep Lifetime is presented for welded joints.In the present method, time-incremental computations of stress by a finite element method and simultaneous cumulations of a variable as a measure of Creep damage are reiterated up to the critical time for the cumulative value to exceed a specified limit. This critical time is regarded as the Creep Lifetime.A butt-welded joint of 50 mm thick Type 304 stainless steel was prepared by SAW with depositing a 308 wire. Specimens cut from the joint were subjected to Creep tests at 823 K under applied stresses of 200 to 300 MPa. The obtained data was compared with the computations.The comparison showed that the Creep Lifetime of the joint predicted from the computations is within the factor of two (one half to two times) of that measured.
Eric Andrieu - One of the best experts on this subject based on the ideXlab platform.
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the effect of thermal cycling on the high temperature Creep behaviour of a single crystal nickel based superalloy
Scripta Materialia, 2007Co-Authors: Aymeric Raffaitin, Daniel Monceau, Fabrice Crabos, Eric AndrieuAbstract:Isothermal and thermal cycling Creep behaviours of a single crystal nickel-based superalloy have been studied by means of tensile tests at 1150 °C and 80 MPa. We have demonstrated that thermal cycling Creep rates are faster than isothermal Creep rates and that Lifetimes at high temperatures are shorter for Creep tests under thermal cycling conditions. Furthermore, it is shown that thermal cycling Creep Lifetime increases as the thermal cycle frequency decreases.
Chen Liqing - One of the best experts on this subject based on the ideXlab platform.
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Creep properties and effect factors of hot continuous rolled Ti–6Al–4V alloy
Materials Science and Engineering: A, 2011Co-Authors: Tian Sugui, Bao Xianyu, Chen LiqingAbstract:Abstract By means of heat treatment, measurement of Creep properties and contract analysis of dislocations configuration, Creep behaviors and effect factors of hot continuous rolled (HCR) Ti–6Al–4V alloy are investigated. Results show that, the microstructure of HCR alloy after solution treatment at temperature lower than β phase transus point consists of the super-saturation equiaxial α phase and “basket weave” structure. The quantity of “basket weave” structure increases with solution temperature, and the fully “basket weave” structure may be obtained after solution treatment at 1000 °C. Compared to the alloy solution treated at 940 °C, the alloy treated at 1000 °C has lower strain rate and longer Creep Lifetime under the conditions of applied stress of 575 MPa at 420 °C. In the range of the applied stress and temperature, the Creep activation energy of the alloy is calculated to be Q a = 249.8 kJ/mol. Deformation mechanism of HCR alloy during Creep is double orientations slips of dislocations activated within α phase with HCP structure, while deformation feature of the alloy solution treated at 940 °C is the wave-like 〈a + c〉 dislocations activated on the pyramidal planes in the α phase. Solution treated at 1000 °C, deformation mechanism of the alloy is that the multiple slips of (1/2)〈1 1 1〉 dislocations are activated within β phase with BCC structure, in which V-rich β phase with high volume fraction may enhance Creep resistance, which is thought to be the main reason of the alloy possessing the low strain rate and longer Creep Lifetime.