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Han Mei - One of the best experts on this subject based on the ideXlab platform.
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Transverse Stress-Rupture Properties of Single Crystal Superalloy DD6 at Mediate Temperature
Journal of Materials Engineering, 2009Co-Authors: Han MeiAbstract:The transverse Stress-Rupture properties of the second generation single crystal superalloy DD6 were investigated at 800, 850, 900℃. The results show that the transverse Stress-Rupture lives are less than the longitudinal, i.e. the [001]-oriented. At relatively higher temperatures, the transverse Stress-Rupture lives approach quantitatively to the longitudinal, while at relatively lower temperature the transverse Stress-Rupture lives are obviously less than the longitudinal. With temperature increasing, the diffusion has more effects on the creep of the alloy, as makes the deformation between dendrite cores and interdenditic regions uniform so that the transverse Stress-Rupture properties relatively increase and approach to the longituadinal. That the transverse Stress-Rupture properties are inferior to the [001]-oriented results mainly from the primary dendrite interfaces and interdendritic regions, which are perpendicular to Stress axis and must sustain the full load.
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Effects of Low Angle Grain Boundaries on Stress Rupture Properties of Single Crystal Superalloy DD6
Journal of Aeronautical Materials, 2007Co-Authors: Han MeiAbstract:The effects of low angle grain boundaries(LABs) on the Stress Rupture properties of second generation single crystal superalloy DD6 were investigated at 800℃,850℃ and 900℃.The Stress Rupture properties of DD6 with LABs tended to decrease with angle increasing,and were rather low when the angles of LAB were relatively larger.Meanwhile the Stress Rupture properties of DD6 alloy with \ orientation were superior to those of the alloy with LABs.When the angles of LABs were relatively lower,the Stress Rupture properties of DD6 with LABs were lower than those of the alloy with \ orientation at the condition of 800℃;however,the Stress Rupture properties of DD6 with LABs approached quantitatively to those of the alloy with \ orientation at the conditions of 850℃ and 900℃,indicating that the effects of LABs on Rupture properties decreased with temperature increasing.
Shi-zhong Liu - One of the best experts on this subject based on the ideXlab platform.
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Stress Rupture Properties and Fracture Behavior of DD6 Single Crystal Superalloy
Materials Science Forum, 2016Co-Authors: Zhen-xue Shi, Shi-zhong Liu, Mei HanAbstract:The Stress Rupture properties, fracture behavior and microstructure evolution of the second generation single crystal superalloy DD6 at different conditions were investigated. The results show that the alloy has excellent Stress Rupture properties. The fracture mechanism of Stress Rupture of the alloy at 760°C/785MPa, 760°C/750MPa and 760°C/720MPa shows quasi-cleavage mode and the fracture mechanism at 980°C/250MPa, 1070°C/160MPa and 1100°C/140MPa shows dimple mode, while the fracture mechanism at 850°C/550MPa shows quasi-cleavage and dimple mixture mode. Only a little change in the morphology of γ′ phase occurred at 760°C/750MPa. The γ′ rafts form at temperature above 760°C and the thickness of rafts increases with increasing temperature. The dislocation shear mechanism including stacking fault formation is operative at lower temperature and high Stress. The dislocation by-passing mechanism occurs to form networks at γ/γ′ interface under the condition of high temperature and lower Stress.
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Influence of Cooling Method on the Microstructure and Stress Rupture Property of a Single Crystal Superalloy
Materials Science Forum, 2015Co-Authors: Zhen-xue Shi, Shi-zhong Liu, Xiao-guang WangAbstract:The single crystal superalloy with [001] orientation were prepared by screw selecting method in the directionally solidified furnace. Three different cooling method, water cooling (WC), air cooling (AC) and furnace cooling (FC) were used after same solution treatment. Then these specimens received same two-step aging treatment. Influence of solution cooling method on the microstructure and Stress Rupture properties of the alloy under the test condition of 980 °C and 300 MPa was investigated. The microstructures of the samples were examined by scanning electron microscope (SEM). The results showed that the solution cooling method of heat treatment played an important role in the microstructure and Stress Rupture properties of the alloy. The size of γ′ phase and the width of the γ matrix channel of the alloy increased with decreasing cooling rate. The Stress Rupture properties of the alloy increased at first and decreased afterwards with decreasing cooling rate. The alloy with air cooling (AC) has the best Stress Rupture properties. The γ′ phase changed into a perfect raft structure during the Stress Rupture process of the specimens with AC method. However, the γ′ phase changed into a very irregular raft microstructure in the specimens with the water cooling (WC) and furnace cooling (FC) method. The micro-cracks in the specimen with irregular raft make the initiation and interconnection easier than that in the specimen with regular raft. Therefore, the alloy with AC method has optimum microstructure and Stress Rupture property.
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Effect of Ru on Stress Rupture properties of nickel-based single crystal superalloy at high temperature
Transactions of Nonferrous Metals Society of China, 2012Co-Authors: Zhen-xue Shi, Shi-zhong Liu, Xiao-guang Wang, Xiao-dai YueAbstract:Abstract Two experimental single crystal superalloys, Ru-free alloy and Ru-containing alloy with [001] orientation, other alloying element contents being basically kept same, were cast in the directionally solidified furnace. The effect of Ru on the Stress Rupture properties of the single crystal superalloy was investigated at (980°C, 250 MPa), (1100°C, 140 MPa) and (1120°C, 140 MPa). The results show that Ru can enhance high temperature Stress Rupture properties of single crystal superalloy. The improvement effect of Ru addition on Stress Rupture properties decreases with increasing test temperature. The γ′ coarsening and rafting directionally are observed in Ru-free alloy and Ru-containing alloy after Stress Rupture test. Needle shaped TCP phases precipitated in both of alloys after Stress Rupture test at (1100°C, 140 MPa) and (1120°C, 140 MPa) and no TCP phase was observed in both of alloys after Stress Rupture test (980°C, 250 MPa). The precipitate volume fraction of TCP phases is significantly decreased by the addition of Ru. At last, the relationship between the microstructure change with Ru addition and improvement of Stress Rupture properties was discussed.
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Effects of Dendritic Orientation on Stress Rupture Properties of DD6 Single Crystal Superalloy
Journal of Iron and Steel Research International, 2011Co-Authors: Zhen-xue Shi, Shi-zhong Liu, Jin-qian ZhaoAbstract:Abstract DD6 single crystal superalloy slabs were prepared with seed method in the directionally solidified furnace with high temperature gradient. The transverse Stress Rupture properties and fracture behaviour of the alloy at 760 °C/758 MPa, 850 °C/550 MPa and 980 °C/250 MPa were investigated and compared with those of longitudinal specimens. The transverse Stress Rupture lives are corresponding with the longitudinal Stress Rupture lives at 760 °C/758 MPa and 850 °C/550 MPa. The transverse Stress Rupture lives are slightly less than the longitudinal Stress Rupture lives at 980 °C/250 MPa. The fracture mechanism of the transverse Stress Rupture of the alloy at 760 °C/758 MPa shows quasi-cleav-age mode and the fracture mechanism at 980 °C/250 MPa shows dimple mode, while the fracture mechanism at 850 °C/550 MPa shows quasi-cleavage and dimple mixture mode. At higher temperature and lower Stress, the microcracks are easier to initiate and interconnect in the transverse specimen than those in longitudinal specimen because there are interdendritic regions perpendicular to the axis of Stress.
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Stress Rupture Properties of the Second Generation Single Crystal Superalloy DD6 after High Temperature Exposure
Materials Science Forum, 2007Co-Authors: Hai Peng Jin, Shi-zhong LiuAbstract:The effects of high temperature exposure simulating service conditions on Stress Rupture properties were studied for the second generation single crystal superalloy DD6. The specimens with [001] orientation were exposed in air at temperatures of 980°C and 1070°C for 100h to 1000h. They were then tested using conventional mechanical tests at 1070°C/140MPa to determine the effects of exposure on Stress Rupture properties. The analysis indicated that Stress Rupture life decreased with increasing exposure time. At the temperature of 980°C, the Stress Rupture life is more than 180h after exposure for 1000h. When the test temperature increased to 1070°C, the Stress Rupture life exceeds 100h after 800h exposure. The morphology of γ prime phase after exposure was observed by using scanning electron microscopy (SEM). Morphologies evaluations have shown that alloy DD6 exhibits excellent microstructure stability after exposure. TCP (Topologically Closed Packed) phases have not been observed. It has been also found that the morphology and size of γ prime affected Stress Rupture life of the alloy. The decrement in Stress Rupture life with increasing exposure is a result of γ prime rafting.
Xueshan Xiao - One of the best experts on this subject based on the ideXlab platform.
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Effects of Alloy Elements on Oxidation Resistance and Stress-Rupture Property of P92 Steel
Acta Metallurgica Sinica (english Letters), 2014Co-Authors: Gang Liu, Xueshan Xiao, Caixiong Yang, Xi-min Chen, Xiao-ke Zhang, Xiang-jun MengAbstract:Effects of alloy elements Cr, W, Ce, and Si on oxidation behavior at 750 °C in air and Stress-Rupture properties of P92 steel have been investigated. The proper increase in elements Cr, W, and Ce improved to varying degrees both oxidation resistance by either facilitating more protective Cr2O3 or modifying surface morphologies and Stress-Rupture life largely attributed to the formation of fine Laves phase. The excessive addition of Si significantly improved oxidation resistance of P92 steel, but dramatically impaired the Stress-Rupture life due to the formation and coarsening of Laves phase. The results indicate that proper additions of Cr, W, and Ce are beneficial for the comprehensive property of P92 steel.
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microstructure evolution and Stress Rupture properties of nimonic 80a after various heat treatments
Materials & Design, 2013Co-Authors: Caixiong Yang, Xueshan Xiao, Qingxuan Ran, Xiuli Cao, Guoqing JiaAbstract:Abstract Four heat treatments have been designed to produce multi-modal size distributions of γ′ phase in γ matrix, and Stress-Rupture properties of Nimonic 80A have been investigated. The γ′ phase exhibits two typical coherent orientation relationships with γ matrix. The fine γ′ particles are in spherical shape when the average size is about 20 nm. However, the coarse γ′ particles present a cuboidal shape with round corners when they are larger than 75 nm. The Al and Ti elements diffuse from γ matrix to γ′ phase, and about 80% Al and Ti are used to form γ′ phase after various heat treatments. The increased volume fraction of the fine γ′ particles with average size of 15.8–20.3 nm increases the Stress-Rupture life of Nimonic 80A at 750 °C/310 MPa. The rod-like Cr 23 C 6 carbide at grain boundary can suppress grain boundary sliding at high temperature and benefit the Stress-Rupture life. The coarse γ′ particles facilitate the movement of dislocations and contribute to the ductility. The precipitate of multi-modal size distributions of γ′ phase is beneficial to the Stress-Rupture ductility.
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Improvement of Stress-Rupture life of GTD-111 by second solution heat treatment
Materials & Design, 2013Co-Authors: Caixiong Yang, Zixing Zhang, Xueshan Xiao, Heng Nie, Guoqing Jia, Zhi ShenAbstract:Abstract An added second solution heat treatment was conducted to investigate its effects on the microstructures and Stress-Rupture properties of GTD-111. The microstructures were analyzed by scanning electron microscope after each step of heat treatments. The Stress-Rupture life of GTD-111 dramatically increases from about 180 to 288 h at 871 °C/310 MPa after adding a second solution heat treatment. The added second solution heat treatment promoted the solution of γ – γ ′ eutectic into γ matrix, and facilitated the nucleation and precipitate of the secondary γ ′ particles. The distribution of γ ′ phase becomes much denser, the width of γ matrix channel is also reduced, and the volume fraction of γ ′ phase significantly increases from about 29.3% to 44.2%. The improved Stress-Rupture life is primarily due to the increased volume fraction of γ ′ phase. The carbides mainly consist of MC and a small amount of M 23 C 6 , which may prevent the dislocation moving and/or grain boundary sliding, and further improve the Stress-Rupture properties of GTD-111.
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relationship between ti al ratio and Stress Rupture properties in nickel based superalloy
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2012Co-Authors: Lei Zhang, Xueshan Xiao, Guoqing Jia, Xiuli Cao, Zhi ShenAbstract:Abstract Microstructural analyses have been carried out to investigate the relationship between Ti/Al ratio and Stress-Rupture properties of nickel-based superalloy Ni–19.5Cr–(0.8–3.5)Al–(0.5–3.2)Ti–0.06C. The γ′ phase coherently precipitates in the γ matrix, the volume fraction and average diameter of the spherical γ′ phase decrease slightly with the increase of Ti/Al ratio after full heat treatment. The precipitate of β-NiAl in the γ matrix for the alloys with low Ti/Al ratio leads to the propagation of cracking into the grain interior. High Ti/Al ratio leads to the precipitate of η-Ni3Ti at grain boundaries, which weakens the strength of grain boundaries. Both the precipitates of β-NiAl and η-Ni3Ti phases are harmful to the Stress-Rupture life and a peak Stress-Rupture life appears when Ti/Al ratio is about 1.22 with elongation and reduction in area higher than 5% and 9.7%, respectively.
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Improvement of Stress-Rupture Life for Modified-HR6W Austenitic Stainless Steel
Journal of Materials Science & Technology, 2011Co-Authors: Shiyun Cui, Zixing Zhang, Xueshan Xiao, Changchun ZhuAbstract:Stress-Rupture life of HR6W austenitic stainless steel modified with B and Mg additions was measured, and the microstructures were analyzed by optical microscopy, X-ray diffraction, scanning electron microscopy and transmission electron microscopy equipped with energy dispersive spectroscopy The results indicated that the enhancement of the Stress-Rupture life was mainly due to the precipitation with B in the elemental form at the grain boundaries, and the improvement of the form of carbides at grain boundaries and the removal of O and S elements by addition of Mg. The micro-alloying elements have a beneficial effect on Stress-Rupture life of the modified-HR6W austenitic stainless steel at high temperature.
Xiaofeng Sun - One of the best experts on this subject based on the ideXlab platform.
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High Temperature Stress Rupture Anisotropy of a Ni-Based Single Crystal Superalloy
Journal of Materials Science & Technology, 2016Co-Authors: Guanglei Wang, Xiaofeng Sun, Jinlai Liu, Jide Liu, Tao Jin, Xudong Sun, Hu ZhuangqiAbstract:High temperature Stress Rupture anisotropies of a second generation Ni-base single crystal (SC) superalloy specimens with [001], [011] and [111] orientations under 900 °C/445 MPa and 1100 °C/100 MPa have been investigated in the present study, with attentions to the evolution of γ/γ′ microstructure observed by scanning electron microscopy and the dislocation configuration characterized by transmission electron microscopy in each oriented specimen. At 1100 °C/100 MPa as well as 900 °C/445 MPa, the single crystal superalloy exhibits obvious Stress Rupture anisotropic behavior. The [001] oriented specimen has the longest Rupture lifetime at 900 °C/445 MPa, and the [111] oriented sample shows the best Rupture strength at 1100 °C/100 MPa. While the [011] oriented specimen presents the worst Rupture lifetime at each testing condition, its Stress Rupture property at 1100 °C/100 MPa is clearly improved, compared with 900 °C/445 MPa. The evident Stress Rupture anisotropy at 900 °C/445 MPa is mainly attributed to the distinctive movement way of dislocations in each oriented sample. Whereas, at 1100 °C/100 MPa, together with the individual dislocation configuration, the evolution of γ/γ′ microstructure in each orientation also plays a key role in the apparent Stress Rupture anisotropy.
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Temperature dependence of anisotropic Stress-Rupture properties of nickel-based single crystal superalloy SRR99
Transactions of Nonferrous Metals Society of China, 2011Co-Authors: Guo-ming Han, Yan-hong Yang, Xiaofeng SunAbstract:Abstract In order to reveal the temperature dependence of anisotropic Stress-Rupture behavior of SRR99 single crystal superalloys under conditions of temperature ranging from 650 to 1 040 °C and typical Stresses, fracture morphologies and microstructure evolution were investigated by SEM and TEM. From the Larson-Miller curves, it is found that single crystal with [001] orientation has the optimum Stress Rupture property in comparison with [011] and [111] orientations at lower and intermediate temperature. With increasing temperature to 1 040 °C, Stress-Rupture properties of single crystals with three principal orientations tend to be equivalent. Based on the fracture surface and microstructural observations, superior Stress-Rupture behavior of single crystal with [001] orientation was rationalized and the effect of misorientation of single crystal on Stress Rupture property was also discussed.
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Anisotropic Stress Rupture properties of the nickel-base single crystal superalloy SRR99
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2010Co-Authors: Guo-ming Han, Yuan Sun, Xiaofeng SunAbstract:The influence of orientation on the Stress Rupture properties of a single crystal superalloy SRR99 was investigated at temperatures of 760 and 1040 degrees C. It is found that the creep anisotropic behaviour is pronounced at the lower temperature of 760 degrees C and the Stress Rupture life ranks in the order [0 0 1] > [1 1 1] > [0 1 1]. Despite the anisotropy of Stress Rupture life is evidently reduced at the higher temperature, the [1 1 1] orientation exhibits the longest life. At 760 degrees C, EBSD (electron back scattered diffraction) was adopted to measure the lattice rotation and the deduced results indicate that the dominant slip systems are (1 1 2) {1 1 1} during Stress Rupture test. At 1040 degrees C, the ranking order of the Stress Rupture life is [1 1 1] > [0 0 1] > [0 1 1] and the single crystal close to [0 1 1] orientation still shows the poorest life. In the [0 0 1] and [1 1 1] samples, regular-gamma raft structure is formed compared with [0 1 1] samples. Further observations made by TEM investigations reveal the underlying deformation mechanisms for crystals with orientations near [0 0 1], [0 1 1] and [1 1 1] under two test conditions. (C) 2010 Elsevier B.V. All rights reserved.
Zhi Shen - One of the best experts on this subject based on the ideXlab platform.
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Improvement of Stress-Rupture life of GTD-111 by second solution heat treatment
Materials & Design, 2013Co-Authors: Caixiong Yang, Zixing Zhang, Xueshan Xiao, Heng Nie, Guoqing Jia, Zhi ShenAbstract:Abstract An added second solution heat treatment was conducted to investigate its effects on the microstructures and Stress-Rupture properties of GTD-111. The microstructures were analyzed by scanning electron microscope after each step of heat treatments. The Stress-Rupture life of GTD-111 dramatically increases from about 180 to 288 h at 871 °C/310 MPa after adding a second solution heat treatment. The added second solution heat treatment promoted the solution of γ – γ ′ eutectic into γ matrix, and facilitated the nucleation and precipitate of the secondary γ ′ particles. The distribution of γ ′ phase becomes much denser, the width of γ matrix channel is also reduced, and the volume fraction of γ ′ phase significantly increases from about 29.3% to 44.2%. The improved Stress-Rupture life is primarily due to the increased volume fraction of γ ′ phase. The carbides mainly consist of MC and a small amount of M 23 C 6 , which may prevent the dislocation moving and/or grain boundary sliding, and further improve the Stress-Rupture properties of GTD-111.
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relationship between ti al ratio and Stress Rupture properties in nickel based superalloy
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2012Co-Authors: Lei Zhang, Xueshan Xiao, Guoqing Jia, Xiuli Cao, Zhi ShenAbstract:Abstract Microstructural analyses have been carried out to investigate the relationship between Ti/Al ratio and Stress-Rupture properties of nickel-based superalloy Ni–19.5Cr–(0.8–3.5)Al–(0.5–3.2)Ti–0.06C. The γ′ phase coherently precipitates in the γ matrix, the volume fraction and average diameter of the spherical γ′ phase decrease slightly with the increase of Ti/Al ratio after full heat treatment. The precipitate of β-NiAl in the γ matrix for the alloys with low Ti/Al ratio leads to the propagation of cracking into the grain interior. High Ti/Al ratio leads to the precipitate of η-Ni3Ti at grain boundaries, which weakens the strength of grain boundaries. Both the precipitates of β-NiAl and η-Ni3Ti phases are harmful to the Stress-Rupture life and a peak Stress-Rupture life appears when Ti/Al ratio is about 1.22 with elongation and reduction in area higher than 5% and 9.7%, respectively.