The fracture modes of low alloy steels and cast irons under tensile and fatigue conditions were identified by electron back-scattered diffraction（EBSD） misorientation analysis in this research. The curves of grain r...The fracture modes of low alloy steels and cast irons under tensile and fatigue conditions were identified by electron back-scattered diffraction（EBSD） misorientation analysis in this research. The curves of grain reference orientation deviation（GROD） distribution perpendicular to the fracture surface were obtained by EBSD observation, and the characteristics of each fracture mode were identified. The GROD value of the specimen fractured in tension decreases to a constant related to the elongation of corresponding specimen in the far field（farther than 5 mm away from the fracture surface）. The peak exhibits in GROD curves of two smooth specimens and a notched specimen near the fracture surface（within 5 mm away from the fracture surface）, and the formation mechanisms were discussed in detail based on the influences of specimen geometries（smooth or notched） and material toughness. The GROD value of fatigue fractured specimen is close to that at undeformed condition in the whole field, except the small area near the crack path. The loading conditions（constant stress amplitude loading or constant stress intensity factor range K loading） and the EBSD striation formation during fatigue crack propagation were also studied by EBSD observation parallel to the crack path.展开更多
The microstructures of pearlitic steel wire rods and steel wires are commonly characterized by secondary electron imaging (SEI)technique using scanning electron microscopy(SEM).In this work,a back-scattered electron i...The microstructures of pearlitic steel wire rods and steel wires are commonly characterized by secondary electron imaging (SEI)technique using scanning electron microscopy(SEM).In this work,a back-scattered electron imaging(BSEI)method is proposed to determine the microstructures of undeformed and deformed pearlitic steels with nanometer scale pearlite lamellae.The results indicate that BSEI technique can characterize the pearlite lamellas veritably and is effective in quantitative measurement of the mean size of pearlite interlamellar spacing.To some extent,BSEI method is more suitable than SEI technique for studying undeformed and not severely deformed pearlitic steels.展开更多
By using iterative method to solve the vector radiative transfer equation of discrete scatterers with randomly rough under-boundary, the back-scattering coefficient is derived, and is applied to the two-scale model of...By using iterative method to solve the vector radiative transfer equation of discrete scatterers with randomly rough under-boundary, the back-scattering coefficient is derived, and is applied to the two-scale model of sea surface with foam scatterers driven by strong wind. By employing the modified probability density function of Cox and Munk's, and Pierson's sea spectrum, numerical results of polarized back-scatter ing are calculated. The functional dependence on wind speed and direction, observation angle, polarization and other parameters are discussed, and theoretical results are favorably matched with experimental data.展开更多
The modal back-scattering matrix can be extracted from reverberation data. For high frequency cases the ’window smoothed’ processing has been proposed by E. C. Shang, T. F. Gao and D. J. Tang (2002) to extract the ...The modal back-scattering matrix can be extracted from reverberation data. For high frequency cases the ’window smoothed’ processing has been proposed by E. C. Shang, T. F. Gao and D. J. Tang (2002) to extract the ’window averaged’ back-scattering matrix. It is pointed out in this paper that in order to inverse the ’window averaged’ back-scattering matrix by changing the source depth data we have to assume that the matrix is not related to the source depth, and the numerical simulation on the question has been conducted.展开更多
A large number of anomalous extension twins,with low or even negative twinning Schmid factors,were found to nucleate and grow in a strongly textured Mg-1Al alloy during tensile deformation along the extruded direction...A large number of anomalous extension twins,with low or even negative twinning Schmid factors,were found to nucleate and grow in a strongly textured Mg-1Al alloy during tensile deformation along the extruded direction.The deformation mechanisms responsible for this behaviour were investigated through in-situ electron back-scattered diffraction,grain reference orientation deviation,and slip trace-modified lattice rotation.It was found that anomalous extension twins nucleated mainly at the onset of plastic deformation at or near grain boundary triple junctions.They were associated with the severe strain incompatibility between neighbour grains as a result from the differentbasal slip-induced lattice rotations.Moreover,the anomalous twins were able to grow with the applied strain due to the continuous activation ofbasal slip in different neighbour grains,which enhanced the strain incompatibility.These results reveal the complexity of the deformation mechanisms in Mg alloys at the local level when deformed along hard orientations.展开更多
An AZ41 magnesium alloy in the hot-rolled condition without further thermomechanical processing to modify its microstructure was investigated to establish its suitability for use within a superplastic forming process ...An AZ41 magnesium alloy in the hot-rolled condition without further thermomechanical processing to modify its microstructure was investigated to establish its suitability for use within a superplastic forming process and to establish optimum forming parameters.Formability was assessed using elevated temperature tensile testing and hot gas bulging,across a range of strain rates(1×10^(−1)−1×10^(−3)s^(−1))and temperatures(350−450℃).Circle grid analysis with GOM Aramis cameras was used to understand peak strains and material thinning in relation to industrial forming processes.Post forming EBSD and STEM analysis was conducted to understand the mechanisms responsible for the materials formability,with dynamic recrystallization being clearly evident.Peak elongation of 520%was achieved at 450℃ and 1×10^(−3)s^(−1);industrially relevant elongation was achieved at 1×10^(−2) s^(−1) at both 450℃(195%)and 400℃(170%).展开更多
An experimental study of dwell and normal cyclic fatigue behaviours was carried out using specimens from a Ti60 forging with a bimodal microstructure. Apparent decrease in the fatigue life was found under dwell fatigu...An experimental study of dwell and normal cyclic fatigue behaviours was carried out using specimens from a Ti60 forging with a bimodal microstructure. Apparent decrease in the fatigue life was found under dwell fatigue condition as compared to that under normal cyclic condition. Strain produced in each cycle in dwell fatigued specimens was observed larger than that in its normal cyclic-fatigued counterparts. Interior crack initiation was found in most dwell fatigued specimens as compared to the subsurface crack initiation under normal cyclic fatigue condition. Flat and bright facets were found at crack initiation sites in both cases. The facet density is higher in dwell condition, which is consistent with the crystal orientation and Schmid factors analysis of α grains around secondary cracks using electron back-scattered diffraction （EBSD） methods. Dwell loading favours cleavage in α grains with their basal plane normals aligned no more than 15° to the loading axis, which may account for its lower fatigue life according to the present study.展开更多
Based on experimental data of positron annihilation technology, electrolyticdissolution technique, electron back-scattered pattern, etc. and by analysis the strengtheningfactors, the strengthening mechanism of ultra-t...Based on experimental data of positron annihilation technology, electrolyticdissolution technique, electron back-scattered pattern, etc. and by analysis the strengtheningfactors, the strengthening mechanism of ultra-thin hot strip of low carbon steel produced by CSP(Compact Strip Production) technique was investigated. The value of each strengthening mechanism andits contribution percentage to yield strength were achieved. The results show that refinementstrengthening is the predominant strengthening mode; precipitation strengthening and dislocationstrengthening are second to it, their contributions to yield strength are almost equal.展开更多
In this work,the factors affecting asphaltenes deposition in high-temperature and high-pressure wells were studied using backscattered light and PVT equipment customized to suit the well conditions.In an examination o...In this work,the factors affecting asphaltenes deposition in high-temperature and high-pressure wells were studied using backscattered light and PVT equipment customized to suit the well conditions.In an examination of the intensity of backscattered light,it was revealed that there exists a linear relationship between temperature and asphaltene precipitation within a specific temperature range.Within this range,a decrease in temperature tends to accelerate asphaltene precipitation.However,the impacts of pressure and gas-oil ratio are more pronounced.The pressure depletion induces the asphaltenes to precipitate out of the solution,followed by the formation of flocs below the bubble point.In addition,an increase in the gas-oil ratio causes a more severe asphaltene deposition,shifting the location of asphaltenes to deep well sections.展开更多
The microstructure, mechanical properties, and misorientation of automobile beam steels produced by EAF-CSP process were studied using optical microscopy （OM） and electron back-scattered diffraction （EBSD）. It is ...The microstructure, mechanical properties, and misorientation of automobile beam steels produced by EAF-CSP process were studied using optical microscopy （OM） and electron back-scattered diffraction （EBSD）. It is shown that the microstructure of strips is mainly polygonal ferrite, and the average grain size is about 5-8 μm. The electron back-scattered diffraction results show that grain boundaries in ferrite are basically high-angle grain boundaries without remarkable preferred orientation. Hot strips of automobile beam steels possess a good combination of strength and plasticity because of their fine microstructures and low quantity of impurities.展开更多
The significant occupancy of {411}〈148〉texture exists in the thin-gauge grain-oriented silicon steel(TGCRGO is defined that thickness of the sheet is〈0.25 mm and the reduction in cold rolling is more than 90%) whic...The significant occupancy of {411}〈148〉texture exists in the thin-gauge grain-oriented silicon steel(TGCRGO is defined that thickness of the sheet is〈0.25 mm and the reduction in cold rolling is more than 90%) which has been considered to have obviously effects on the abnormal growth of Goss-oriented grains during the secondary recrystallization process. The microstructures of the TG-CRGO were investigated by X-ray diffraction and electron back-scattered diffraction in this study. It was found that {411}〈148〉〉texture mainly exists in the center layer of hot-rolled as well as normalized plates.With the increase in cold rolling reduction, {411}〈148〉 orientation gradually rotates to a-fiber texture(〈110〉//RD).Finally, few {411}〈148〉would retain at the boundaries of deformed a-fiber grains(〈110〉//RD) as the reduction in cold rolling reaches 90%. After annealing treatment, a small amount of c-fiber textures(〈111〉//ND) preferably nucleates and recrystallizes between the DBs(deformation bands) at first; then, the {411}〈148〉 recrystallization texture occurs and mainly nucleates at the grains boundaries of the deformed a-fiber grains, and also quite a few {411}〈148〉orientation grains nucleate in the inner of {112}〈110〉grains. But this phenomenon was not observed in the {100}〈011〉deformation grains.With respect to the occurrence of {411}〈148〉recrystallization texture, it is mainly induced by strong a-fiber as well as weak c-fiber textures formed during cold rolling other than originating from {411}〈148〉 regions in hot bands.展开更多
Micron-scale face-centered cubic titanium phase（named as δ phase） were noticed in the re-melted zone of laser surface re-melted commercially pure titanium plate.The morphology,sub-structure,orientation and distribu...Micron-scale face-centered cubic titanium phase（named as δ phase） were noticed in the re-melted zone of laser surface re-melted commercially pure titanium plate.The morphology,sub-structure,orientation and distribution of δ phase were investigated by scanning electron microscopy,electron back-scattered diffraction and transmission electron microscopy.Three kind formation processes of δ phase were put forward based on the investigation.The first one is α＇→δ transformation which takes place in single α＇grains and leads to the orientation relationship {001}δ//{0001}α＇〈 110 〉 δ//〈 112^-0 〉α＇.The second one is β→α＇＋ δ transformation which takes place at α＇/α＇interfaces and leads to the orientation relationship{001}δ//{11^-0}β〈110〉 δ//〈111〉β.The third one is another kind of β→α＇＋ δ transformation that takes place at α＇/α＇interfaces and leads to the orientation relationship{11^-1}δ//{11^-0}β〈 110 〉 δ//〈 111 〈 β.It is believed that the transformations of δ phase are stress assistant ones and in the present investigation,the phase transformation stress of β→α＇transformation acts as the assistant driving force for the formation of δ phase.展开更多
The grain refinement mechanism and texture evolution of electromagnetically formed polycrystalline Cu sheets were investigated using the electron back-scattered diffraction(EBSD) technique. It is found that the averag...The grain refinement mechanism and texture evolution of electromagnetically formed polycrystalline Cu sheets were investigated using the electron back-scattered diffraction(EBSD) technique. It is found that the average grain size decreases from 35.88 μm to 8.77 μm. The grain refinement was mainly attributed to dynamic recrystallization(DRX) at the grain boundary regions of bulged Cu samples where the inhomogeneous dislocation density and the large lattice misorientation were observed. The DRX mechanisms at the grain boundaries were discussed with respect to the strain-induced grain boundary migration nucleation. Moreover, the orientation distribution function(ODF) of the sample with the strain of 50% demonstrated a strong {110}<211> texture and a relatively weak {001}<100> texture. The texture evolution was discussed using the plastic work values of the grains with various orientations, which were calculated according to the Taylor model and the virtual work principle. The experimental results show that the expended plastic work of the grains with {110} orientation is 9.69 MPa, which is distinctly higher than those of the grains with the {001} and {111} orientations. This indicates that the formation of the {110} orientated texture would be preferred with increasing strain in good agreement with the experimental result.展开更多
By optical inspection of macro-etched metallography and electron back-scattered diffraction （EBSD） mapping, this paper analyzed the microstructure of austenitic stainless steel strips produced with an equal-diameter...By optical inspection of macro-etched metallography and electron back-scattered diffraction （EBSD） mapping, this paper analyzed the microstructure of austenitic stainless steel strips produced with an equal-diameter twin-roll strip caster. The results indicate that the microstructure of the strips includes two columnar zones with highly compact dendrites and one equiaxed zone. The characteristics, such as grain size and growing direction of columnar grains and equiaxed grains, were investigated. An additional transitional area with many finer grains between the columnar zone and the equiaxed zone was found. As shown in EBSD analysis, small angle boundaries exist both in the columnar zone and the equiaxed zone, although they are especially more in the transitional area. Additionally, some 〈111〉 twin boundaries were found in the microstructure of the strips.展开更多
The influence of a self-focused beam on the stimulated Raman scattering(SRS)process in collisional plasma is explored.Here,collisional nonlinearity arises as a result of non-uniform heating,thereby causing carrier red...The influence of a self-focused beam on the stimulated Raman scattering(SRS)process in collisional plasma is explored.Here,collisional nonlinearity arises as a result of non-uniform heating,thereby causing carrier redistribution.The plasma density profile gets modified in a perpendicular direction to the main beam axis.This modified plasma density profile greatly affects the pump wave,electron plasma wave(EPW)and back-scattered wave.The well-known paraxial theory and Wentzel-Kramers-Brillouin approximation are used to derive second-order ordinary differential equations for the beam waists of the pump wave,EPW and the scattered wave.Further to this,the well-known fourth-order Runge-Kutta method is used to carry out numerical simulations of these equations.SRS back-reflectivity is found to increase due to the focusing of several waves involved in the process.展开更多
The effect of scattering on the transmission of subwavelength Si nanorod arrays is investigated. It is found that the distance between the nanorods has important effect on the transmission because the scattered light ...The effect of scattering on the transmission of subwavelength Si nanorod arrays is investigated. It is found that the distance between the nanorods has important effect on the transmission because the scattered light varies largely with it. When the nanorods are close to each other, the back-scattered light and the light reflected by the surface of substrates interfere destructively and lead to a high transmission. When the distance of the nanorods increases, the intensity of the scattered light decrease and this makes the transmission decrease. The reflection and the transmission of the nanorod arrays can be adjusted by changing the distance between the neighbouring nanorods.展开更多
Microstructure and texture of electrodeposited Cu micro-cylinders in the blind hole play a vitally im- portant role in the electrical and mechanical properties of the three-dimensional （3-D） IC （integrated circuit...Microstructure and texture of electrodeposited Cu micro-cylinders in the blind hole play a vitally im- portant role in the electrical and mechanical properties of the three-dimensional （3-D） IC （integrated circuit）/Si integrations. In this paper, a new commercial additive system, which is specifically devel- oped for the high-aspect-ratio through-silicon-via （TSV） filling, was used to electrodeposit Cu in the blind holes. The microstructure of electrodeposited Cu micro-cylinder in the blind hole with a diameter of 40 μm and a depth of 140 μm was investigated by electron back-scattered diffraction （EBSD） technique. Grain size distribution of the Cu micro-cylinder in the blind hole differed from the bottom to the top. The grain boundaries contained a high fraction of Z3 CSL （coincident site lattice） boundaries. It has been reported that the Cu overburden film on the surface of the blind hole influenced the crystallographic orientation of Cu grains inside the damascene trench. So the effects of the current density and additive concentra- tion on the crystal structure of the overburden Cu film were also studied in this study. The experimental results indicated that the preferred orientation of the Cu overburden film changed from {111} to {220} when the current density increased from 2 to 80 mA cm-2. However, the effect of additives on the crystal structure of the Cu overburden film was dependent on the crystal structure of the seed layer.展开更多
Experiment were conducted to unidirectional solidification pure copper during ECAP by route C, the samples were investigated by XRD and EBSD. The results shown that the effect of original microstructure on the subgrai...Experiment were conducted to unidirectional solidification pure copper during ECAP by route C, the samples were investigated by XRD and EBSD. The results shown that the effect of original microstructure on the subgrains orientation decrease with the increasing of strain. At low strain, in the column grain interiors first formed a band structure that the orientation quite different with the matrix. With the strain increasing, the boundaries of the band structure expanding towards to two sides, gradually partition the original column grains into subgrains, the distribution of the subgrains possesses a directional distribution characteristics and the twins occurring in subgrains. Keep on increasing strain, the original grain boundaries began to broken, low angles grain boundaries and high angles grain boundaries both occur simultaneously shows a diffusion distribution characteristics.展开更多
During the deformation of Mg alloys,{10-12}extension twin often contributes to the formation of basal texture but rarely assists the nucleation of recrystallization,i.e.,effective grain refinement,therefore it seems t...During the deformation of Mg alloys,{10-12}extension twin often contributes to the formation of basal texture but rarely assists the nucleation of recrystallization,i.e.,effective grain refinement,therefore it seems to make against the improvement of formability and mechanical properties.In this work,{10-12}extension twin has been creatively utilized as a preference nucleation site for static recrystallization(SRX),achieving grain refinement and orientation randomization in a Mg-Gd-Y alloy using multi-directional impact forging(MDIF)and subsequent annealing treatment.Effect of{10-12}extension twin on SRX behavior has been investigated by annealing treatment at 450℃using quasi-in-situ optical microscopy(OM)and quasi-in-situ electron back-scattering diffraction(EBSD).The microstructural evolution during annealing shows that several SRX gains can nucleate from the grain boundary of untwinned grains,but they only have few influences on the final microstructure due to their limited volume faction and sluggish growth.In contrast,a large number of SRX gains can initiate from{10-12}extension twin and grow up without the confine of twin boundaries.Finally,they consume their parent grains and make the main contribution to grain refinement.This should be attributed to those pinned{10-12}twin boundary,by interacting with various dislocation slips during the MDIF process,which can operate like grain boundary,store enough strain energy,and promote the nucleation of SRX during annealing.On the other hand,SRX grains usually keep initial random orientation and further randomize the forging texture during annealing treatment.展开更多
The compression of soil grain and pore fluid as well as viscid coupling of pore fluid and soil skeleton is considered, the scattering problem of incident plane P1 wave （fast compressional wave） by an infinite cylind...The compression of soil grain and pore fluid as well as viscid coupling of pore fluid and soil skeleton is considered, the scattering problem of incident plane P1 wave （fast compressional wave） by an infinite cylindrical shell deeply embedded in isotropic saturated soils is studied by adopting the amended Biot model, amplitude equations about potential functions of scattering and refracting fields are obtained, and the effect of dimensionless frequencies and shell thickness on the back-scattering spectra and dynamic stress concentration factors of two types of cylindrical shells with high and low rigidity are numerically computed and analyzed.展开更多
基金financially supported by Mitsubishi Heavy Industries,Ltd.,Japanthe National Natural Science Foundation of China(Nos.11572171,11632010 and U1533134)the opening project(No.KFJJ15-12M)of State Key Laboratory of Explosion Science and Technology(Beijing Institute of Technology)
文摘The fracture modes of low alloy steels and cast irons under tensile and fatigue conditions were identified by electron back-scattered diffraction（EBSD） misorientation analysis in this research. The curves of grain reference orientation deviation（GROD） distribution perpendicular to the fracture surface were obtained by EBSD observation, and the characteristics of each fracture mode were identified. The GROD value of the specimen fractured in tension decreases to a constant related to the elongation of corresponding specimen in the far field（farther than 5 mm away from the fracture surface）. The peak exhibits in GROD curves of two smooth specimens and a notched specimen near the fracture surface（within 5 mm away from the fracture surface）, and the formation mechanisms were discussed in detail based on the influences of specimen geometries（smooth or notched） and material toughness. The GROD value of fatigue fractured specimen is close to that at undeformed condition in the whole field, except the small area near the crack path. The loading conditions（constant stress amplitude loading or constant stress intensity factor range K loading） and the EBSD striation formation during fatigue crack propagation were also studied by EBSD observation parallel to the crack path.
基金supported by the National Key Technology R&D Program of China(Grant No.2007BAE15B01)the Major Program of the National Natural Science Foundation of China(Grant No.50890170)
文摘The microstructures of pearlitic steel wire rods and steel wires are commonly characterized by secondary electron imaging (SEI)technique using scanning electron microscopy(SEM).In this work,a back-scattered electron imaging(BSEI)method is proposed to determine the microstructures of undeformed and deformed pearlitic steels with nanometer scale pearlite lamellae.The results indicate that BSEI technique can characterize the pearlite lamellas veritably and is effective in quantitative measurement of the mean size of pearlite interlamellar spacing.To some extent,BSEI method is more suitable than SEI technique for studying undeformed and not severely deformed pearlitic steels.
基金This work was supported by the National Natural Science Foundation of ChinaFok Ying Tung Education Foundation
文摘By using iterative method to solve the vector radiative transfer equation of discrete scatterers with randomly rough under-boundary, the back-scattering coefficient is derived, and is applied to the two-scale model of sea surface with foam scatterers driven by strong wind. By employing the modified probability density function of Cox and Munk's, and Pierson's sea spectrum, numerical results of polarized back-scatter ing are calculated. The functional dependence on wind speed and direction, observation angle, polarization and other parameters are discussed, and theoretical results are favorably matched with experimental data.
文摘The modal back-scattering matrix can be extracted from reverberation data. For high frequency cases the ’window smoothed’ processing has been proposed by E. C. Shang, T. F. Gao and D. J. Tang (2002) to extract the ’window averaged’ back-scattering matrix. It is pointed out in this paper that in order to inverse the ’window averaged’ back-scattering matrix by changing the source depth data we have to assume that the matrix is not related to the source depth, and the numerical simulation on the question has been conducted.
基金supported by the project(MAD2DCM)-IMDEA Materials funded by Comunidad de Madrid and by the Recovery,Transformation and Resilience Plan and by NextGenerationEU from the European Union,and by the María de Maeztu seal of excellence from the Spanish Research Agency(CEX2018-000800-M)Mr.B.Yang wishes to express his gratitude for the support of the China Scholarship Council(202106370122).
文摘A large number of anomalous extension twins,with low or even negative twinning Schmid factors,were found to nucleate and grow in a strongly textured Mg-1Al alloy during tensile deformation along the extruded direction.The deformation mechanisms responsible for this behaviour were investigated through in-situ electron back-scattered diffraction,grain reference orientation deviation,and slip trace-modified lattice rotation.It was found that anomalous extension twins nucleated mainly at the onset of plastic deformation at or near grain boundary triple junctions.They were associated with the severe strain incompatibility between neighbour grains as a result from the differentbasal slip-induced lattice rotations.Moreover,the anomalous twins were able to grow with the applied strain due to the continuous activation ofbasal slip in different neighbour grains,which enhanced the strain incompatibility.These results reveal the complexity of the deformation mechanisms in Mg alloys at the local level when deformed along hard orientations.
基金The authors would like to thank the WMG High Value Manufacturing Catapult Centre for funding this work.In addition,the characterisation facility is supported from the Higher Education Funding Council for England(HEFCE).
文摘An AZ41 magnesium alloy in the hot-rolled condition without further thermomechanical processing to modify its microstructure was investigated to establish its suitability for use within a superplastic forming process and to establish optimum forming parameters.Formability was assessed using elevated temperature tensile testing and hot gas bulging,across a range of strain rates(1×10^(−1)−1×10^(−3)s^(−1))and temperatures(350−450℃).Circle grid analysis with GOM Aramis cameras was used to understand peak strains and material thinning in relation to industrial forming processes.Post forming EBSD and STEM analysis was conducted to understand the mechanisms responsible for the materials formability,with dynamic recrystallization being clearly evident.Peak elongation of 520%was achieved at 450℃ and 1×10^(−3)s^(−1);industrially relevant elongation was achieved at 1×10^(−2) s^(−1) at both 450℃(195%)and 400℃(170%).
文摘An experimental study of dwell and normal cyclic fatigue behaviours was carried out using specimens from a Ti60 forging with a bimodal microstructure. Apparent decrease in the fatigue life was found under dwell fatigue condition as compared to that under normal cyclic condition. Strain produced in each cycle in dwell fatigued specimens was observed larger than that in its normal cyclic-fatigued counterparts. Interior crack initiation was found in most dwell fatigued specimens as compared to the subsurface crack initiation under normal cyclic fatigue condition. Flat and bright facets were found at crack initiation sites in both cases. The facet density is higher in dwell condition, which is consistent with the crystal orientation and Schmid factors analysis of α grains around secondary cracks using electron back-scattered diffraction （EBSD） methods. Dwell loading favours cleavage in α grains with their basal plane normals aligned no more than 15° to the loading axis, which may account for its lower fatigue life according to the present study.
基金This work was financially supported by the state foundation for key projects: Fundamental Research on New Generation of Steels (No: G1998061500).
文摘Based on experimental data of positron annihilation technology, electrolyticdissolution technique, electron back-scattered pattern, etc. and by analysis the strengtheningfactors, the strengthening mechanism of ultra-thin hot strip of low carbon steel produced by CSP(Compact Strip Production) technique was investigated. The value of each strengthening mechanism andits contribution percentage to yield strength were achieved. The results show that refinementstrengthening is the predominant strengthening mode; precipitation strengthening and dislocationstrengthening are second to it, their contributions to yield strength are almost equal.
基金This work was supported by the National Natural Science Foundation of China(No.52174047)the China Scholarship Council(No.202106440102)the PetroChina Strategic Cooperation Science and Technology Project(No.ZLZX 2020-01).
文摘In this work,the factors affecting asphaltenes deposition in high-temperature and high-pressure wells were studied using backscattered light and PVT equipment customized to suit the well conditions.In an examination of the intensity of backscattered light,it was revealed that there exists a linear relationship between temperature and asphaltene precipitation within a specific temperature range.Within this range,a decrease in temperature tends to accelerate asphaltene precipitation.However,the impacts of pressure and gas-oil ratio are more pronounced.The pressure depletion induces the asphaltenes to precipitate out of the solution,followed by the formation of flocs below the bubble point.In addition,an increase in the gas-oil ratio causes a more severe asphaltene deposition,shifting the location of asphaltenes to deep well sections.
基金This work was financially supported by the National Natural Science Foundation of China (No. 50334010)
文摘The microstructure, mechanical properties, and misorientation of automobile beam steels produced by EAF-CSP process were studied using optical microscopy （OM） and electron back-scattered diffraction （EBSD）. It is shown that the microstructure of strips is mainly polygonal ferrite, and the average grain size is about 5-8 μm. The electron back-scattered diffraction results show that grain boundaries in ferrite are basically high-angle grain boundaries without remarkable preferred orientation. Hot strips of automobile beam steels possess a good combination of strength and plasticity because of their fine microstructures and low quantity of impurities.
基金financially supported by the China’s State Grid Corporation of Science and Technology Projects (No. SGRI-WD-71-13-002)the National Natural Science Foundation of China (No. 51171019)
文摘The significant occupancy of {411}〈148〉texture exists in the thin-gauge grain-oriented silicon steel(TGCRGO is defined that thickness of the sheet is〈0.25 mm and the reduction in cold rolling is more than 90%) which has been considered to have obviously effects on the abnormal growth of Goss-oriented grains during the secondary recrystallization process. The microstructures of the TG-CRGO were investigated by X-ray diffraction and electron back-scattered diffraction in this study. It was found that {411}〈148〉〉texture mainly exists in the center layer of hot-rolled as well as normalized plates.With the increase in cold rolling reduction, {411}〈148〉 orientation gradually rotates to a-fiber texture(〈110〉//RD).Finally, few {411}〈148〉would retain at the boundaries of deformed a-fiber grains(〈110〉//RD) as the reduction in cold rolling reaches 90%. After annealing treatment, a small amount of c-fiber textures(〈111〉//ND) preferably nucleates and recrystallizes between the DBs(deformation bands) at first; then, the {411}〈148〉 recrystallization texture occurs and mainly nucleates at the grains boundaries of the deformed a-fiber grains, and also quite a few {411}〈148〉orientation grains nucleate in the inner of {112}〈110〉grains. But this phenomenon was not observed in the {100}〈011〉deformation grains.With respect to the occurrence of {411}〈148〉recrystallization texture, it is mainly induced by strong a-fiber as well as weak c-fiber textures formed during cold rolling other than originating from {411}〈148〉 regions in hot bands.
基金financially supported by the Natural Science Foundation of Beijing (Grant No.Z140002)
文摘Micron-scale face-centered cubic titanium phase（named as δ phase） were noticed in the re-melted zone of laser surface re-melted commercially pure titanium plate.The morphology,sub-structure,orientation and distribution of δ phase were investigated by scanning electron microscopy,electron back-scattered diffraction and transmission electron microscopy.Three kind formation processes of δ phase were put forward based on the investigation.The first one is α＇→δ transformation which takes place in single α＇grains and leads to the orientation relationship {001}δ//{0001}α＇〈 110 〉 δ//〈 112^-0 〉α＇.The second one is β→α＇＋ δ transformation which takes place at α＇/α＇interfaces and leads to the orientation relationship{001}δ//{11^-0}β〈110〉 δ//〈111〉β.The third one is another kind of β→α＇＋ δ transformation that takes place at α＇/α＇interfaces and leads to the orientation relationship{11^-1}δ//{11^-0}β〈 110 〉 δ//〈 111 〈 β.It is believed that the transformations of δ phase are stress assistant ones and in the present investigation,the phase transformation stress of β→α＇transformation acts as the assistant driving force for the formation of δ phase.
基金Funded by the National Fundamental Research Program of China(No.2011CB012806)
文摘The grain refinement mechanism and texture evolution of electromagnetically formed polycrystalline Cu sheets were investigated using the electron back-scattered diffraction(EBSD) technique. It is found that the average grain size decreases from 35.88 μm to 8.77 μm. The grain refinement was mainly attributed to dynamic recrystallization(DRX) at the grain boundary regions of bulged Cu samples where the inhomogeneous dislocation density and the large lattice misorientation were observed. The DRX mechanisms at the grain boundaries were discussed with respect to the strain-induced grain boundary migration nucleation. Moreover, the orientation distribution function(ODF) of the sample with the strain of 50% demonstrated a strong {110}<211> texture and a relatively weak {001}<100> texture. The texture evolution was discussed using the plastic work values of the grains with various orientations, which were calculated according to the Taylor model and the virtual work principle. The experimental results show that the expended plastic work of the grains with {110} orientation is 9.69 MPa, which is distinctly higher than those of the grains with the {001} and {111} orientations. This indicates that the formation of the {110} orientated texture would be preferred with increasing strain in good agreement with the experimental result.
基金supported by the National Natural Science Foundation of China (No. 50434040)
文摘By optical inspection of macro-etched metallography and electron back-scattered diffraction （EBSD） mapping, this paper analyzed the microstructure of austenitic stainless steel strips produced with an equal-diameter twin-roll strip caster. The results indicate that the microstructure of the strips includes two columnar zones with highly compact dendrites and one equiaxed zone. The characteristics, such as grain size and growing direction of columnar grains and equiaxed grains, were investigated. An additional transitional area with many finer grains between the columnar zone and the equiaxed zone was found. As shown in EBSD analysis, small angle boundaries exist both in the columnar zone and the equiaxed zone, although they are especially more in the transitional area. Additionally, some 〈111〉 twin boundaries were found in the microstructure of the strips.
文摘The influence of a self-focused beam on the stimulated Raman scattering(SRS)process in collisional plasma is explored.Here,collisional nonlinearity arises as a result of non-uniform heating,thereby causing carrier redistribution.The plasma density profile gets modified in a perpendicular direction to the main beam axis.This modified plasma density profile greatly affects the pump wave,electron plasma wave(EPW)and back-scattered wave.The well-known paraxial theory and Wentzel-Kramers-Brillouin approximation are used to derive second-order ordinary differential equations for the beam waists of the pump wave,EPW and the scattered wave.Further to this,the well-known fourth-order Runge-Kutta method is used to carry out numerical simulations of these equations.SRS back-reflectivity is found to increase due to the focusing of several waves involved in the process.
文摘The effect of scattering on the transmission of subwavelength Si nanorod arrays is investigated. It is found that the distance between the nanorods has important effect on the transmission because the scattered light varies largely with it. When the nanorods are close to each other, the back-scattered light and the light reflected by the surface of substrates interfere destructively and lead to a high transmission. When the distance of the nanorods increases, the intensity of the scattered light decrease and this makes the transmission decrease. The reflection and the transmission of the nanorod arrays can be adjusted by changing the distance between the neighbouring nanorods.
基金sponsored by Chinese National Science and Technology Major Project (No. 2011ZX02702-003)
文摘Microstructure and texture of electrodeposited Cu micro-cylinders in the blind hole play a vitally im- portant role in the electrical and mechanical properties of the three-dimensional （3-D） IC （integrated circuit）/Si integrations. In this paper, a new commercial additive system, which is specifically devel- oped for the high-aspect-ratio through-silicon-via （TSV） filling, was used to electrodeposit Cu in the blind holes. The microstructure of electrodeposited Cu micro-cylinder in the blind hole with a diameter of 40 μm and a depth of 140 μm was investigated by electron back-scattered diffraction （EBSD） technique. Grain size distribution of the Cu micro-cylinder in the blind hole differed from the bottom to the top. The grain boundaries contained a high fraction of Z3 CSL （coincident site lattice） boundaries. It has been reported that the Cu overburden film on the surface of the blind hole influenced the crystallographic orientation of Cu grains inside the damascene trench. So the effects of the current density and additive concentra- tion on the crystal structure of the overburden Cu film were also studied in this study. The experimental results indicated that the preferred orientation of the Cu overburden film changed from {111} to {220} when the current density increased from 2 to 80 mA cm-2. However, the effect of additives on the crystal structure of the Cu overburden film was dependent on the crystal structure of the seed layer.
文摘Experiment were conducted to unidirectional solidification pure copper during ECAP by route C, the samples were investigated by XRD and EBSD. The results shown that the effect of original microstructure on the subgrains orientation decrease with the increasing of strain. At low strain, in the column grain interiors first formed a band structure that the orientation quite different with the matrix. With the strain increasing, the boundaries of the band structure expanding towards to two sides, gradually partition the original column grains into subgrains, the distribution of the subgrains possesses a directional distribution characteristics and the twins occurring in subgrains. Keep on increasing strain, the original grain boundaries began to broken, low angles grain boundaries and high angles grain boundaries both occur simultaneously shows a diffusion distribution characteristics.
基金financially supported by the National Key Research and Development Program of China(No.2016YFB0301104)the National Natural Science Foundation of China(Nos.51531002,51301173,51601193 and 51701218)+1 种基金the National Science and Technology Major Project of China(No.2017ZX04014001)the Natural Science Foundation of Liaoning province(No.20180550799)。
文摘During the deformation of Mg alloys,{10-12}extension twin often contributes to the formation of basal texture but rarely assists the nucleation of recrystallization,i.e.,effective grain refinement,therefore it seems to make against the improvement of formability and mechanical properties.In this work,{10-12}extension twin has been creatively utilized as a preference nucleation site for static recrystallization(SRX),achieving grain refinement and orientation randomization in a Mg-Gd-Y alloy using multi-directional impact forging(MDIF)and subsequent annealing treatment.Effect of{10-12}extension twin on SRX behavior has been investigated by annealing treatment at 450℃using quasi-in-situ optical microscopy(OM)and quasi-in-situ electron back-scattering diffraction(EBSD).The microstructural evolution during annealing shows that several SRX gains can nucleate from the grain boundary of untwinned grains,but they only have few influences on the final microstructure due to their limited volume faction and sluggish growth.In contrast,a large number of SRX gains can initiate from{10-12}extension twin and grow up without the confine of twin boundaries.Finally,they consume their parent grains and make the main contribution to grain refinement.This should be attributed to those pinned{10-12}twin boundary,by interacting with various dislocation slips during the MDIF process,which can operate like grain boundary,store enough strain energy,and promote the nucleation of SRX during annealing.On the other hand,SRX grains usually keep initial random orientation and further randomize the forging texture during annealing treatment.
文摘The compression of soil grain and pore fluid as well as viscid coupling of pore fluid and soil skeleton is considered, the scattering problem of incident plane P1 wave （fast compressional wave） by an infinite cylindrical shell deeply embedded in isotropic saturated soils is studied by adopting the amended Biot model, amplitude equations about potential functions of scattering and refracting fields are obtained, and the effect of dimensionless frequencies and shell thickness on the back-scattering spectra and dynamic stress concentration factors of two types of cylindrical shells with high and low rigidity are numerically computed and analyzed.
