Effects of hot extrusion (HEX) and heat treatment on prior particle boundary (PPB), MC carbides,γ′precipitates and grain size of nickel-base FGH96 superalloy were studied. The results show that PPB consists of larg...Effects of hot extrusion (HEX) and heat treatment on prior particle boundary (PPB), MC carbides,γ′precipitates and grain size of nickel-base FGH96 superalloy were studied. The results show that PPB consists of largeγ′, MC carbides enriched with Ti, Nb and a modicum of oxides. Thereafter, it can efficaciously tune γ′ precipitate size from micrometer down to nanometer region and simultaneously results in the annihilation of PPB by HEX process. The activation energy for grain growth of as-HEXed FGH96 superalloy was measured to be 402.6 kJ/mol, indicating that γ′ precipitate serves the critical role in inhibiting grain growth under sub-solvus heat treatment. Moreover, the results reveal that grain growth is primarily restrained by MC carbide in the case of super-solvus temperature.展开更多
A crystal plasticity model is developed to predict the cyclic plasticity during the low-cycle fatigue of GH4169 superalloy.Accumulated plastic slip and energy dissipation as fatigue indicator parameters(FIPs)are used ...A crystal plasticity model is developed to predict the cyclic plasticity during the low-cycle fatigue of GH4169 superalloy.Accumulated plastic slip and energy dissipation as fatigue indicator parameters(FIPs)are used to predict fatigue crack initiation and the fatigue life until failure.Results show that fatigue damage is most likely to initiate at triple points and grain boundaries where severe plastic slip and energy dissipation are present.The predicted fatigue life until failure is within the scatter band of factor 2 when compared with experimental data for the total strain amplitudes ranging from 0.8%to 2.4%.Microscopically,the adjacent grain arrangements and their interactions account for the stress concentration.In addition,different sets of grain orientations with the same total grain numbers of 150 were generated using the present model.Results show that different sets have significant influence on the distribution of stresses between each individual grain at the meso-scale,although little effect is found on the macroscopic length-scale.展开更多
The creep rupture properties of a single crystal superalloy were tested at 975℃/255 MPa as a function of the deviation degrees from [001].The misorientation of the specimens away from [001] distributed approximately ...The creep rupture properties of a single crystal superalloy were tested at 975℃/255 MPa as a function of the deviation degrees from [001].The misorientation of the specimens away from [001] distributed approximately along a line between [001]-[011] and [001]-[111] boundaries in the triangle of the stereographic projection.Creep rupture lifetimes of the specimens were not sensitive to the misorientation until the deviation degree exceeded ～30 deg.Two steps of lattice rotation were found in all specimens during creep,first towards the [001]-[111] boundary,and then to [001] or [111] along the boundary.Single slip and strong asymmetric deformation were observed during the first stage of lattice rotation in specimens with large misorientation.The rotation mechanism was associated with the activated slip systems according to the calculated Schmid factors.The impact of lattice rotation on the rupture properties was also discussed.展开更多
Orthogonal experiment is employed to study a new kind of multiplex flux for nickel-base superalloy. This activated TIG welding flux is composed of NaF, MgF2 and CaF2, and their proportion is 5：4：1. Compared with con...Orthogonal experiment is employed to study a new kind of multiplex flux for nickel-base superalloy. This activated TIG welding flux is composed of NaF, MgF2 and CaF2, and their proportion is 5：4：1. Compared with conventional TIG welding, the penetration increases 164% by the action of the flux. Tensile test result indicates that the fracture strength of the mixed flux A-TIG weld bead is higher than base metal, and it increases along with the decrement of the welding current. The average extensibility of the weldment is beyond 100%, which means perfect ductility. MetaUographs elucidate that there exist lots of deep and evenly distributed dimples on the fiacture section of weld bead while on that of base metal there only exists a few shallow dimples and massive tearing ridge.展开更多
Evolution of the morphology of MC carbides with the change of cooling rate and carbon content in two kinds of nickel-base superalloys, K417 G and DD33, has been investigated. The morphology of MC carbides evolves from...Evolution of the morphology of MC carbides with the change of cooling rate and carbon content in two kinds of nickel-base superalloys, K417 G and DD33, has been investigated. The morphology of MC carbides evolves from faceted to script-like with increasing cooling rate. Varying the carbon content from 40X10-6 to 320X10-6, the morphology of carbides changes from blocky, rod-like into script-like. Scanning electron microscopy observation of deep-etched samples indicates that these carbides evolve from octahedral to dendritic and then into welldeveloped dendrites accordingly in a three-dimensional manner. The morphology evolution is discussed from the viewpoint of the preferential growth orientation of fcc crystals and the carbide growth rate during directional solidification.展开更多
The phase transformation temperature, segregation behavior of elements and as-cast microstructure were investigated in experimental nickel-base superalloys with different levels of carbon and boron. The results show t...The phase transformation temperature, segregation behavior of elements and as-cast microstructure were investigated in experimental nickel-base superalloys with different levels of carbon and boron. The results show that the liquidus temperature decreases gradually but the carbide solvus temperature increases obviously with increasing carbon addition. Minor boron addition to the alloy decreases the liquidus temperature, carbide solvus temperature and solidus temperature slightly. Apart from rhenium, the segregation coefficients of the elements alter insignificantly with the addition of carbon. The segregation behavior of rhenium, tungsten and tantalum become more severe with boron addition. The volume fraction and size of primary carbides increase with increasing carbon addition. The main morphology of the carbides is script-like in the alloys with carbon addition while the carbide sheets tend to be concentrated and coarse in the boron-containing alloys展开更多
The coarsening behavior of γ particles in a nickel-base superalloy FGH95 was investigated by means of experimental observations and growth kinetics calculations. The results show that when aging at 1000,1080 and 1140...The coarsening behavior of γ particles in a nickel-base superalloy FGH95 was investigated by means of experimental observations and growth kinetics calculations. The results show that when aging at 1000,1080 and 1140°C for different times,the relation of average particle size to time obeys the cube law ( a /2)3= kt,where k is 15.49 × 103,77.5 × 103 and 230.04 × 103 nm3/min,respectively. The particle size distributions are better fit to the LSW theoretical distributions when aging at 1000°C within 1440 min....展开更多
基金Project(2012AA03A514)supported by the National High-Tech Research and Development Program of ChinaProject(2013M531803)supported by the Postdoctoral Science Foundation of China+1 种基金Project(74341016096)supported by the Postdoctoral Science Foundation of Central South University,ChinaProject(2013RS4031)supported by the Hunan Provincial Science and Technology Plan,China
文摘Effects of hot extrusion (HEX) and heat treatment on prior particle boundary (PPB), MC carbides,γ′precipitates and grain size of nickel-base FGH96 superalloy were studied. The results show that PPB consists of largeγ′, MC carbides enriched with Ti, Nb and a modicum of oxides. Thereafter, it can efficaciously tune γ′ precipitate size from micrometer down to nanometer region and simultaneously results in the annihilation of PPB by HEX process. The activation energy for grain growth of as-HEXed FGH96 superalloy was measured to be 402.6 kJ/mol, indicating that γ′ precipitate serves the critical role in inhibiting grain growth under sub-solvus heat treatment. Moreover, the results reveal that grain growth is primarily restrained by MC carbide in the case of super-solvus temperature.
基金supported financially by the National Natural Sciene Foundation of China(Nos.51725503 and 51575183)111 Project+4 种基金Zhang XC is also grateful for the support by Shanghai Pujiang ProgramYoung Scholar of the Yangtze River Scholars ProgramShanghai Technology Innovation Program of SHEITC(No.CXY-2015-001)financial supports by Coventry University through the Early Career Researcher-Outgoing Mobility Awardthe East China University of Science and Technology through 111 Project to facilitate this international research collaboration.
文摘A crystal plasticity model is developed to predict the cyclic plasticity during the low-cycle fatigue of GH4169 superalloy.Accumulated plastic slip and energy dissipation as fatigue indicator parameters(FIPs)are used to predict fatigue crack initiation and the fatigue life until failure.Results show that fatigue damage is most likely to initiate at triple points and grain boundaries where severe plastic slip and energy dissipation are present.The predicted fatigue life until failure is within the scatter band of factor 2 when compared with experimental data for the total strain amplitudes ranging from 0.8%to 2.4%.Microscopically,the adjacent grain arrangements and their interactions account for the stress concentration.In addition,different sets of grain orientations with the same total grain numbers of 150 were generated using the present model.Results show that different sets have significant influence on the distribution of stresses between each individual grain at the meso-scale,although little effect is found on the macroscopic length-scale.
基金sponsored by the National Basic Research Program of China (Grant No.2010CB631201)the National Natural Science Foundation of China (Grant No.50931004)
文摘The creep rupture properties of a single crystal superalloy were tested at 975℃/255 MPa as a function of the deviation degrees from [001].The misorientation of the specimens away from [001] distributed approximately along a line between [001]-[011] and [001]-[111] boundaries in the triangle of the stereographic projection.Creep rupture lifetimes of the specimens were not sensitive to the misorientation until the deviation degree exceeded ～30 deg.Two steps of lattice rotation were found in all specimens during creep,first towards the [001]-[111] boundary,and then to [001] or [111] along the boundary.Single slip and strong asymmetric deformation were observed during the first stage of lattice rotation in specimens with large misorientation.The rotation mechanism was associated with the activated slip systems according to the calculated Schmid factors.The impact of lattice rotation on the rupture properties was also discussed.
文摘Orthogonal experiment is employed to study a new kind of multiplex flux for nickel-base superalloy. This activated TIG welding flux is composed of NaF, MgF2 and CaF2, and their proportion is 5：4：1. Compared with conventional TIG welding, the penetration increases 164% by the action of the flux. Tensile test result indicates that the fracture strength of the mixed flux A-TIG weld bead is higher than base metal, and it increases along with the decrement of the welding current. The average extensibility of the weldment is beyond 100%, which means perfect ductility. MetaUographs elucidate that there exist lots of deep and evenly distributed dimples on the fiacture section of weld bead while on that of base metal there only exists a few shallow dimples and massive tearing ridge.
基金supported by the National Basic Research Program of China (Grant No. 2010CB631201)the National Natural Science Foundation of China (Grant No. 51201164)
文摘Evolution of the morphology of MC carbides with the change of cooling rate and carbon content in two kinds of nickel-base superalloys, K417 G and DD33, has been investigated. The morphology of MC carbides evolves from faceted to script-like with increasing cooling rate. Varying the carbon content from 40X10-6 to 320X10-6, the morphology of carbides changes from blocky, rod-like into script-like. Scanning electron microscopy observation of deep-etched samples indicates that these carbides evolve from octahedral to dendritic and then into welldeveloped dendrites accordingly in a three-dimensional manner. The morphology evolution is discussed from the viewpoint of the preferential growth orientation of fcc crystals and the carbide growth rate during directional solidification.
基金Projects(2011CB610406,2010CB631202)supported by the National Basic Research Program of ChinaProjects(51101120,50931004,51171151)supported by the National Natural Science Foundation of China
文摘The phase transformation temperature, segregation behavior of elements and as-cast microstructure were investigated in experimental nickel-base superalloys with different levels of carbon and boron. The results show that the liquidus temperature decreases gradually but the carbide solvus temperature increases obviously with increasing carbon addition. Minor boron addition to the alloy decreases the liquidus temperature, carbide solvus temperature and solidus temperature slightly. Apart from rhenium, the segregation coefficients of the elements alter insignificantly with the addition of carbon. The segregation behavior of rhenium, tungsten and tantalum become more severe with boron addition. The volume fraction and size of primary carbides increase with increasing carbon addition. The main morphology of the carbides is script-like in the alloys with carbon addition while the carbide sheets tend to be concentrated and coarse in the boron-containing alloys
基金the National Natural Science Foundation of China (No. 50471097)the Programme of Introducing Talents of Discipline to Chinese Universities (No. B07003).
文摘The coarsening behavior of γ particles in a nickel-base superalloy FGH95 was investigated by means of experimental observations and growth kinetics calculations. The results show that when aging at 1000,1080 and 1140°C for different times,the relation of average particle size to time obeys the cube law ( a /2)3= kt,where k is 15.49 × 103,77.5 × 103 and 230.04 × 103 nm3/min,respectively. The particle size distributions are better fit to the LSW theoretical distributions when aging at 1000°C within 1440 min....
