The Experts below are selected from a list of 66387 Experts worldwide ranked by ideXlab platform
Lanzhang Zhou - One of the best experts on this subject based on the ideXlab platform.
-
microstructural evolution and its influence on the impact toughness of gh984g alloy during long term Thermal Exposure
Journal of Materials Science & Technology, 2021Co-Authors: Xuezhi Qin, Changshuai Wang, Lanzhang ZhouAbstract:Abstract The microstructure evolution and its effect on the impact toughness of a new Ni-Fe based alloy GH984G, used in 700 °C ultra-super critical coal-fired power plant, were investigated during Thermal Exposure at 650 °C–750 °C for up to 10,000 h. The results show that the impact toughness at room temperature drops rapidly at the early stage during Thermal Exposure at 700 °C and then has no significant change even if after Exposure for 10,000 h. The significant decline of the impact toughness is attributed to the coarsening of M23C6 carbides at grain boundaries, which weakens the grain boundary strength and leads to the aging-induced grain boundary embrittlement. The M23C6 carbides have almost no change with further Thermal Exposure and the impact toughness also remains stable. Additionally, the impact toughness rises with the increase of Thermal Exposure temperature. The size of γ′ after Thermal Exposure at 750 °C for 10,000 h is much bigger than that at 650 °C and 700 °C for 10,000 h. Therefore, the intragranular strength decreases significantly due to the transformation of the interaction between γ′ and dislocation from strongly coupled dislocation shearing to Orowan bowing. More plastic deformation occurs within grains after Thermal Exposure at 750 °C for 10,000 h, which increases the impact toughness.
-
effect of ta on microstructural evolution and mechanical properties of a solid solution strengthening cast ni based alloy during long term Thermal Exposure at 700 c
Journal of Alloys and Compounds, 2017Co-Authors: Shuang Gao, Jieshan Hou, Fei Yang, Yongan Guo, Lanzhang ZhouAbstract:Effect of Ta on microstructural evolution and mechanical properties of a solid-solution strengthening cast Ni-based superalloy, IN617B alloy, considered as a potential candidate for castings in 700 degrees C advanced ultra-supercritical (A-USC) coal-fired power plants, has been studied in this paper. Detailed observation reveals the alloys with different contents of Ta have similar solution treated microstructure. During long-term Thermal Exposure at 700 degrees C, Ta addition refines gamma' particles and enhances the Thermal stability of gamma' phase by decreasing the gamma-gamma' lattice misfit. With increasing Ta content the solubility of Mo in matrix decreases, which promotes the transformation of film-like M23C6 at grain boundaries (GBs) into blocky M6C carbide with the reaction of M23C6 -> Mo--Cr(+Mo,Ta) M6C. Consequently, the morphology of GB carbide changes from continuous film structure to dispersed block structure. In addition, local concentration of metal elements leads to the precipitation of trace amount of s phase which is not affected by Ta concentration. Nearly all the tensile properties at 700 degrees C of the alloy after long-term Thermal Exposure are improved noticeably with the increase of Ta content. But, the plasticity of the alloy with 2.0 wt. % Ta addition decreases remarkably due to the excessive Ta content leading to severe M6C coarsening at GBs. The alloy achieves optimal mechanical properties with about 1.0 wt. % Ta content. (C) 2017 Elsevier B.V. All rights reserved.
-
microstructural changes and their effect on tensile properties of a ni fe based alloy during long term Thermal Exposure
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2016Co-Authors: Changshuai Wang, Jianting Guo, Yongan Guo, Lanzhang ZhouAbstract:Abstract Microstructural changes and their effect on tensile properties of a Ni-Fe based alloy, considered as boiler materials in 700 °C advanced ultra-supercritical (A-USC) coal-fired power plants, were investigated during Exposure at 700–800 °C for up to 30000 h. The results show that the major precipitates are still spherical γ׳, blocky MC and discrete particle-like M 23 C 6 after long-term Thermal Exposure. No η or σ and other detrimental phases were observed. The main changes in microstructure are γ′ coarsening and the precipitation and growth of M 23 C 6 carbide. The coarsening behavior of γ′ precipitates is in good accordance with the prediction of the Lifshitz-Slozov-Wagner (LSW) theory during Exposure at 700 °C. However, it deviates from the prediction of LSW theory at 750 and 800 °C and an anomalous coarsening behavior of γ′ precipitates was observed. For M 23 C 6 carbide, the size and amount first increase, and then keep almost constant with increasing Exposure time at 700 and 750 °C, but the dissolution of M 23 C 6 carbide appears at 800 °C. The yield strength first increases and then slightly decreases with increasing Exposure time at 700 °C, while it decreases gradually at 750 °C and decreases drastically and then keeps almost constant at 800 °C. However, the yield strength almost keeps the same level as that of the samples after standard heat treatment even if after Exposure at 700 °C for 30000 h. The elongation has no obvious change with increasing Exposure time at 700 and 750 °C, but it increases gradually at 800 °C. The changes in yield strength and ductility can be attributed to the γ′ coarsening and the evolution of M 23 C 6 carbide.
-
gamma prime stability and its influence on tensile behavior of a wrought superalloy with different fe contents
Journal of Materials Research, 2016Co-Authors: Changshuai Wang, Jianting Guo, Yongan Guo, Lanzhang ZhouAbstract:Gamma prime (γ′) stability and its influence on tensile behavior of a newly developed wrought superalloy with various Fe contents was studied both experimentally and thermodynamically. The results show that the γ′-solvus temperature is higher and γ–γ′ lattice mismatch is bigger in the alloy with the lower Fe content. During long-term Thermal Exposure at 650–750 °C, the coarsening behavior of γ′ precipitates follows Ostwald ripening kinetics and the lower Fe content can decrease the coarsening rate of γ′ precipitates due to the increase of the activation energy for γ′ coarsening. Moreover, the lower Fe content can retard the transformation from γ′ to η phase. The tensile properties of the alloys with different Fe contents are almost same after standard heat treatment. However, after Thermal Exposure, the decrease of tensile strength in the alloy with lower Fe content is less than that of the alloys with higher Fe content due to the improvement of γ′ stability.
-
microstructure stability and mechanical properties of a new low cost hot corrosion resistant ni fe cr based superalloy during long term Thermal Exposure
Materials & Design, 2015Co-Authors: Xuezhi Qin, Langhong Lou, Wen Sun, Jianting Guo, Lanzhang ZhouAbstract:Abstract A new low cost hot-corrosion resistant Ni–Fe–Cr based superalloy is designed and fabricated. The microstructure evolution, mechanical properties and effect of minor Cr variation on the microstructure stability during long-term Thermal Exposure have been investigated in details. Microstructure observations reveal that the new Ni–Fe–Cr based superalloy is constituted of γ matrix, γ′ precipitate, primary MC carbide and grain boundary (GB) M23C6 carbide after standard heat treatment. During long-term Thermal Exposure at 850 °C, the γ′ precipitate coarsens greatly within 3000 h, which significantly degrades the room temperature hardness and stress-rupture life at 800 °C/294 MPa. The primary MC degenerates gradually by reactions of MC + γ → M23C6 + γ′, MC + γ → M23C6 + M6C + γ′ and MC + γ → M23C6 + M6C + η, respectively. The growth of carbide and γ′ along GB changes it from thin discontinuous chain structure to coarse continuous chain structure, which might lead to the intergranular fracture during stress-rupture. In addition, small amount of grain interior (GI) M23C6 carbide precipitates in the matrix, which has negligible influence on the stress-rupture property. Moreover, minor increase of Cr content (from 20% to 21%) extends the precipitating temperature range of σ phase and enhances its precipitating peak temperature, which results in a large amount of σ phase precipitates in the Ni–Fe–Cr based superalloy during long-term Thermal Exposure at 850 °C. The formation of σ phase increases the room temperature hardness but degrades the stress-rupture life and elongation of the Ni–Fe–Cr based superalloy greatly.
L H Lou - One of the best experts on this subject based on the ideXlab platform.
-
effects of heat treatment on microstructural evolution and stress rupture properties of a directionally solidified nickel based superalloy during long term Thermal Exposure
Journal of Materials Engineering and Performance, 2020Co-Authors: Xiangwei Jiang, Peng Song, B Yin, D Wang, Yao Wang, J S Dong, Jie Shen, L H LouAbstract:Effects of a low-temperature solution heat treatment (SHT) below γ′ solvus temperature and a high-temperature partial solution heat treatment (SHT) above γ′ solvus temperature on microstructural evolution and stress rupture properties of a directionally solidified nickel-based superalloy during long-term Thermal Exposure at 900 °C were investigated in detail. The two heat treatments generated different microstructures, e.g., different γ′ sizes and surface fractions of residual γ–γ′ eutectic phase. Carbides in the two heat-treated samples exhibited different microstructural stability during the subsequent long-term Thermal Exposure. The creep lifetime at 870 °C/310 MPa of the samples treated by the high-temperature SHT is more than two times of that treated by the low-temperature SHT, whereas the creep lifetime of the samples treated by the high-temperature partial SHT exhibited a sharp reduction after 1000-h Exposure and then decreased by a steady rate up to 10,000-h Exposure. In comparison, the creep lifetime of the samples treated by the low-temperature SHT exhibits a slower reduction rate from 0- up to 10,000-h Exposure.
-
microstructural degradation and the effects on creep properties of a hot corrosion resistant single crystal ni based superalloy during long term Thermal Exposure
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2018Co-Authors: X W Jiang, G Xie, D Wang, Xiyang Liu, W Zheng, Yunjiang Wang, L H LouAbstract:In the present study, the kinetics of microstructural degradation during long-term Thermal Exposure (LTTE) and the effects on creep deformation mechanisms of a hot corrosion-resistant single-crystal Ni-based superalloy with a low γ′ volume fraction and γ/γ′ lattice misfit were investigated in detail. The kinetic of γ′ coarsening in the experimental alloy conforms well to the Lifshitz–Slyozov–Wagner theory during LTTE at 900 °C up to 10,000 hours. The evolution of γ/γ′ lattice misfit during the LTTE was also investigated by a first attempt. The focused research emphasized on the influences of γ/γ′ lattice misfit evolution after the LTTE on the microstructural degradation, dislocation motion, and different creep mechanisms during high-temperature low-stress creep and high-temperature high-stress creep. The results show that the decreasing of the absolute values of γ/γ′ lattice misfit and change of γ′ size and morphology after the LTTE contribute to the weakening of barrier to the dislocation cutting process into γ′ precipitates during creep and the sharp reduction of stress-rupture lifetime at 950 °C/280 MPa after 1000 hours Exposure. As the applied stress decreased to 230 MPa at 950 °C, the creep mechanisms change from the dislocation cutting through γ′ precipitates at high applied stress to the dislocation glide and climb around γ′ precipitates. The dislocation glide and climb by-pass deformation mechanism were not significantly influenced by the change of γ′ precipitates morphology and magnitude of γ/γ′ mismatch within 1000 hours Thermal Exposure, and the minimum creep rate and creep lifetime after 1000 hours Thermal Exposure were similar to that of the original heat-treated samples.
-
the effect of reheat treatment on microstructure and stress rupture property of a directionally solidified nickel based superalloy after long term Thermal Exposure
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2017Co-Authors: X W Jiang, D Wang, D Wang, L H LouAbstract:Abstract The recovery of microstructure and creep properties of a directionally solidified superalloy after long-term Thermal Exposure was investigated. After reheat treatment, successful restoration of γ′ microstructure is achieved including morphology, size and chemical composition. However, carbides degradations within interior grains and at grain boundaries are irreversible through the reheat treatment. Short and long-term creep rupture properties are effectively improved by the reheat treatment, but cannot be fully recovered compared to that of the original material. During prolonged Thermal and creep Exposure, grain boundary carbides degradation occurred rapidly in comparison with that in the original material, which is regarded as the main reason leading to the reduction of stress rupture lifetime.
-
effect of silicon on microstructure and stress rupture properties of a corrosion resistant ni based superalloy during long term Thermal Exposure
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2016Co-Authors: Tungsheng Liu, G Xie, Jungang Dong, L Wang, L H LouAbstract:Abstract The influence of silicon on microstructure and stress rupture properties of GH3535 nickel-based superalloy during long term Thermal Exposure at 700 °C was investigated. After long term Thermal Exposure, the secondary carbides precipitated along grain boundaries. Si addition induced the formation of M 12 C carbides, while only M 6 C carbides were observed in Si free alloy. The secondary M 12 C carbides exhibited particular orientation relationship with matrix for the alloy with Si, but the secondary M 6 C carbides are incoherent with matrix for the Si free alloy. It is believed that the difference in the types of the secondary carbides was originated from Si. The stress rupture life decreased after 1000 h Thermal Exposure for the Si free alloy, but no noticeable changes could be detected for the alloy with Si. The interface between the secondary M 6 C carbides and matrix became the main site for crack initiation after 1000 h Thermal Exposure for the Si free alloy. But no cracks was detected at the interface between the secondary M 12 C carbides and matrix even after 10,000 h Thermal Exposure, which may be related to the strong interfacial cohesive force between secondary carbides and matrix.
-
effect of long term Thermal Exposure on microstructure and stress rupture properties of gh3535 superalloy
Journal of Materials Science & Technology, 2015Co-Authors: L H Lou, Tungsheng Liu, Jungang Dong, L Wang, Xingtai Zhou, Jian ZhangAbstract:The evolution of microstructure and the stress rupture properties of long term Thermally exposed GH3535 alloy have been investigated. It was found that M6C carbides presented in the solid solution heat treated samples. During long term Thermal Exposure at 700 degrees C, fine M12C carbides precipitated preferentially at grain boundaries. These carbides coexisted with the pre-exiting M6C. The stress rupture life of 700 degrees C/1000 h exposed sample under creep testing at 650 degrees C/324 MPa is 93 h. It is much longer than that of the solid solution samples. No noticeable changes could be detected in both the microstructure and stress rupture lives when the samples were exposed for time longer than 1000 h M12C carbides were found to be beneficial to the creep properties. The cracks initiated at the interface of M6C carbides and matrix, which led to a lower creep rupture life. Copyright (C) 2015, The editorial office of Journal of Materials Science & Technology. Published by Elsevier Limited. All rights reserved.
Peng Song - One of the best experts on this subject based on the ideXlab platform.
-
anisotropy of interface characteristics between nicocraly coating and a hot corrosion resistant ni based single crystal superalloy during Thermal Exposure at different temperatures
Applied Surface Science, 2020Co-Authors: Xiangwei Jiang, Peng Song, Yao Wang, Jiasheng Dong, Langhong LouAbstract:Abstract Effects of crystal orientations and service temperatures on microstructural evolution of a coated hot corrosion resistant Ni-Based single-crystal superalloy containing carbon were investigated. γ′ grains nucleated at the interdiffusion zone (IDZ) and secondary reaction zone (SRZ) with formation of M23C6 and σ phases during Thermal Exposure at 900 °C. But for specimens exposed at 1000 °C, γ grains nucleated at the IDZ with precipitation of secondary MC carbides and many needle-like σ phases precipitated at the substrate-diffusion zone (SDZ). The interfacial microstructure stabilities exhibited opposite anisotropy during the Thermal Exposure at 900 °C and 1000 °C.
-
effects of heat treatment on microstructural evolution and stress rupture properties of a directionally solidified nickel based superalloy during long term Thermal Exposure
Journal of Materials Engineering and Performance, 2020Co-Authors: Xiangwei Jiang, Peng Song, B Yin, D Wang, Yao Wang, J S Dong, Jie Shen, L H LouAbstract:Effects of a low-temperature solution heat treatment (SHT) below γ′ solvus temperature and a high-temperature partial solution heat treatment (SHT) above γ′ solvus temperature on microstructural evolution and stress rupture properties of a directionally solidified nickel-based superalloy during long-term Thermal Exposure at 900 °C were investigated in detail. The two heat treatments generated different microstructures, e.g., different γ′ sizes and surface fractions of residual γ–γ′ eutectic phase. Carbides in the two heat-treated samples exhibited different microstructural stability during the subsequent long-term Thermal Exposure. The creep lifetime at 870 °C/310 MPa of the samples treated by the high-temperature SHT is more than two times of that treated by the low-temperature SHT, whereas the creep lifetime of the samples treated by the high-temperature partial SHT exhibited a sharp reduction after 1000-h Exposure and then decreased by a steady rate up to 10,000-h Exposure. In comparison, the creep lifetime of the samples treated by the low-temperature SHT exhibits a slower reduction rate from 0- up to 10,000-h Exposure.
Zhen-gong Zhou - One of the best experts on this subject based on the ideXlab platform.
-
effects of Thermal Exposure on mechanical behavior of carbon fiber composite pyramidal truss core sandwich panel
Composites Part B-engineering, 2014Co-Authors: Jiayi Liu, Xiang Zhu, Zhen-gong ZhouAbstract:Abstract An experimental study was performed to investigate the effect of high temperature Exposure on mechanical properties of carbon fiber composite sandwich panel with pyramidal truss core. For this purpose, sandwich panels were exposed to different temperatures for different times. Then sandwich panels were tested under out-of-plane compression till failure after Thermal Exposure. Our results indicated that both the Thermal Exposure temperature and time were the important factors affecting the failure of sandwich panels. Severe reductions in residual compressive modulus and strength were observed when sandwich panels were exposed to 300 °C for 6 h. The effect of high temperature Exposure on failure mode of sandwich panel was revealed as well. Delamination and low fiber to matrix adhesion caused by the degradation of the matrix properties were found for the specimens exposed to 300 °C. The modulus and strength of sandwich panels at different Thermal Exposure temperatures and times were predicted with proposed method and compared with measured results. Experimental results showed that the predicted values were close to experimental values.
-
mechanical behavior and failure mechanisms of carbon fiber composite pyramidal core sandwich panel after Thermal Exposure
Journal of Materials Science & Technology, 2013Co-Authors: Jiayi Liu, Zhen-gong ZhouAbstract:An attempt has been made here to evaluate the effect of Thermal Exposure on the mechanical behavior and failure mechanisms of carbon fiber composite sandwich panel with pyramidal truss core under axial compression. Analytical formulae for the collapse strength of composite sandwich panel after Thermal Exposure were derived. Axial compression tests of composite laminates and sandwich panels after Thermal Exposure were conducted at room temperature to assess the degradation caused by the Thermal Exposure. Experimental results showed that the failure of sandwich panel are not only temperature dependent, but are time dependent as well. The decrease in residual compressive strength is mainly attributed to the degradation of the matrix and the degradation of fiber–matrix interface, as well as the formation of cracks and pores when specimens are exposed to high temperature. The measured failure loads obtained in the experiments showed reasonable agreement with the analytical predictions.
H R Guan - One of the best experts on this subject based on the ideXlab platform.
-
effect of Thermal Exposure on stress rupture properties of a re bearing ni base single crystal superalloy
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2010Co-Authors: J J Yu, H R Guan, Z Q HuAbstract:The effect of Thermal Exposure on microstructure and creep properties of a Re bearing single crystal superalloy is investigated. The alloy is exposed at 950 degrees C for 100-2000h. The coarsening behavior of gamma' varies with local position. The gamma' particles in dendrite core and interior secondary arm form raft when aged longer than 100h. The gamma' in periphery of secondary arm can retain cuboidal morphology aged to 2000h in addition to normal growth. The gamma' in interdendrite region develops into irregular raft. The various behavior of gamma' is attributed to the segregation of refractory elements. The MC carbide demonstrates high stability even though it begins to decompose to M(6)C after 500 h Exposure. This is explained from its high contents of Ta and Nb. mu phase precipitates in both dendrite core and interdendrite region when aged more than 100 h, but the mu phase in these two areas have different morphologies, which is attributed to their unique nucleation site and orientation relationship with matrix. The creep lives of exposed samples at 1000 degrees C/280 MPa decrease with increasing of aging time generally, especially, the life of 500 h aged sample drops lower than that of 1000 h aged sample. The degradation of creep life is accounted for based on coarsening of gamma' and deposition of dislocation during Thermal Exposure. (C) 2009 Elsevier B.V. All rights reserved.
-
topologically close packed phase precipitation in a nickel base superalloy during Thermal Exposure
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007Co-Authors: Jinxia Yang, X F Sun, Qiaosong Zheng, H R GuanAbstract:K465 superalloy was Thermally exposed, respectively at 850, 950, 1000, 1050 and 1100 degrees C. During Thermal Exposure, topologically close-packed phases, such as sigma and mu, are precipitated in interdendritic regions where rapid diffusion paths are provided and the TCP forming elements W, Mo, Cr, Co are concentrated. The Exposure temperature is shown to have a great impact on the formation and growth of TCP phases. a phase is readily formed at the lower annealing temperature (below 950 degrees C), having a basket weave or multi-layer structure whereas becomes instable at the higher Exposure temperature above 950 degrees C. The disappearance of mu phase at higher temperature mainly results from the formation of M23C6 and M6C carbides because they can combine with the larger amounts of the a forming element, Cr. The precipitation of mu phase is mainly depended on M6C carbide, and its morphology exhibits coarse needles or platelets. mu phase is stable above 950 degrees C, and the amount of mu phase reaches the peak value at 1000 degrees C, but is decreased above 1000 degrees C. (C) 2007 Elsevier B.V. All rights reserved.
-
microstructural evolution of a single crystal nickel base superalloy during Thermal Exposure
Materials Letters, 2003Co-Authors: Lidan Liu, T Jin, Nie Zhao, Zhida Wang, X F Sun, H R GuanAbstract:Microstructural evolution of a nickel-base single crystal superalloy during Thermal Exposure at 900 and 1000 degreesC was investigated. In addition to growing and linking of gamma' particles, carbides M6C and M23C6 precipitated in this testing alloy. During Exposure at 900 degreesC, M6C carbide precipitated in cubic shape, while at 1000 degreesC, M6C carbide was separated out in needle-like or cubic shape. M23C6 carbide was all precipitated in the gamma matrix channel. The TCP phase was not found in this alloy during Thermal Exposure both at 900 and 1000 degreesC before 1500 h. (C) 2003 Elsevier Science B.V. All rights reserved.
