In this paper, the orange peel defect in the surface range of the st14 steel sheet has been investigated using the electron backscattered diffraction (EBSD) technique. It has been found that the orange peel defect in ...In this paper, the orange peel defect in the surface range of the st14 steel sheet has been investigated using the electron backscattered diffraction (EBSD) technique. It has been found that the orange peel defect in the st14 steel sheet was resulted from the local coarse grains which were produced during hot-rolling due to the critical deformation in dual-phase zone. During deep drawing, the coarse grains with {100}<001> microtexture can slip on the {112}<111> slip system to form bulging and yields orange peel defects, while the coarse grains with {112}<110> orientation do not form the defect as the Schmid factor of {112}<111> slip system in it equals zero.展开更多
In this study,the twinning-detwinning behavior and slip behavior of rolled AZ31 magnesium-alloy plates during a three-step intermittent dynamic compression process along the rolling direction(RD)and normal direction(N...In this study,the twinning-detwinning behavior and slip behavior of rolled AZ31 magnesium-alloy plates during a three-step intermittent dynamic compression process along the rolling direction(RD)and normal direction(ND),are investigated via quasi-in situ electron backscatter diffraction,and the causes of the twinning and detwinning behavior are explained according to Schmid law,local strain coordination,and slip trajectories.It is found that the twins are first nucleated and grow at a compressive strain of 3%along the RD.In addition to the Schmid factor(SF),the strain coordination factor(m’)also influences the selection of the twin variants during the twinning process,resulting in the nucleation of twins with a low SF.During the second and third steps of the application of continuous compressive strains with magnitudes and directions of 3%RD+3%ND and 3%RD+3%ND+2.5%ND,detwinning occurs to different extents.The observation of the detwinning behavior reveals that the order in which multiple twins within the same grain undergo complete detwinning is related to Schmid law and the strain concentration,with a low SF and a high strain concentration promoting complete detwinning.The interaction between slip dislocations and twin boundaries in the deformed grains as well as the pinning of dislocations at the tips of the {1012} tensile twins with a special structure result in incomplete detwinning.Understanding the microstructural evolution and twinning behavior of magnesium alloys under different deformation geometries is important for the development of high-strength and high-toughness magnesium alloys.展开更多
The Al-Si-Mg alloy which can be strengthened by heat treatment is widely applied to the key components of aerospace and aeronautics. Iron-rich intermetallic compounds are well known to be strongly influential on mecha...The Al-Si-Mg alloy which can be strengthened by heat treatment is widely applied to the key components of aerospace and aeronautics. Iron-rich intermetallic compounds are well known to be strongly influential on mechanical properties in Al-Si-Mg alloys. But intermetallic compounds in cast Al-Si-Mg alloy intermetallics are often misidentified in previous metallurgical studies. It was described as many different compounds, such as AlFeSi, Al8Fe2Si, Al5（Fe, Mn）3Si2 and so on. For the purpose of solving this problem, the intermetallic compounds in cast Al-Si alloys containing 0.5% Mg were investigated in this study. The iron-rich compounds in Al-Si-Mg casting alloys were characterized by optical microscope（OM）, scanning electron microscope（SEM）, energy dispersive X-ray spectrometer（EDS）, electron backscatter diffraction（EBSD） and X-ray powder diffraction（XRD）. The electron backscatter diffraction patterns were used to assess the crystallographic characteristics of intermetallic compounds. The compound which contains Fe/Mg-rich particles with coarse morphologies was Al8FeMg3Si6 in the alloy by using EBSD. The compound belongs to hexagonal system, space group P6_2m, with the lattice parameter a=0.662 nm, c=0.792 nm. The β-phase is indexed as tetragonal Al3FeSi2, space group I4/mcm, a=0.607 nm and c=0.950 nm. The XRD data indicate that Al8FeMg3Si6 and Al3FeSi2 are present in the microstructure of Al-7Si-Mg alloy, which confirms the identification result of EBSD. The present study identified the iron-rich compound in Al-Si-Mg alloy, which provides a reliable method to identify the intermetallic compounds in short time in Al-Si-Mg alloy. Study results are helpful for identification of complex compounds in alloys.展开更多
An algorithm for grain reconstruction based on electron backscatter diffraction data was proposed in this paper. This algorithm can well record the original data arrangement when an external file for the reconstructed...An algorithm for grain reconstruction based on electron backscatter diffraction data was proposed in this paper. This algorithm can well record the original data arrangement when an external file for the reconstructed grain（s） was exported for further post-processing. Assisted by an in-house MATLAB program, grain reconstruction, lattice rotations, orientation spreads, and slip system analysis can be performed. The validity of this algorithm has been successfully tested by polycrystalline Ni before and after channel die compression.展开更多
Morphology observation and crystallographic analysis of lath martensite in 13Cr-5Ni steel were investigated by electron backscattering diffraction （EBSD） in a scanning electron microscope. The pole figures of the mi...Morphology observation and crystallographic analysis of lath martensite in 13Cr-5Ni steel were investigated by electron backscattering diffraction （EBSD） in a scanning electron microscope. The pole figures of the microstructure measured by EBSD showed that the martensite in this steel held the Kurdjumov-Sachs （K-S） orientation relationship, and the boundary misorientations after the austenite-martensite transformation were also analyzed. However, not all the 24 possible variants in the K-S relationship were observed in a single prior austenite grain. Sub-blocks with special combinations were observed, which can be explained by the minimization of the total shape strain between the adjacent variants introduced during the martensite transformation and relatively low carbon content in the 13Cr-5Ni steel.展开更多
This study examines the effects of friction stir welding(FSW)and post-weld heat treatment(PWHT)on the grain boundary character distribution and corrosion resistance of cross sectional(top and bottom)regions of nickel-...This study examines the effects of friction stir welding(FSW)and post-weld heat treatment(PWHT)on the grain boundary character distribution and corrosion resistance of cross sectional(top and bottom)regions of nickel-and molybdenum-free high-nitrogen austenitic stainless steel(HNASS).FSW at 400 rpm and 30 mm/min resulted in finer grains(4.18μm)and higher coincident site lattice(CSL)boundaries(32.3%)at the top of the stir zone(SZ)due to dynamic recrystallization(DRX).PWHT at 900℃for 1 h led to grain coarsening(12.91μm the bottom SZ)but enhanced CSL boundaries from 24.6%to 30.2%,improving grain boundary stability.PWHT reduced the kernel average misorientation(KAM)by 14.9%in the SZ-top layer and 20.4%in the SZ-bottom layer,accompanied by a 25%decrease in hardness in the SZ-top layer and 26.7%in the SZ-bottom layer,indicating strain recovery and reduced dislocation density.Potentiodynamic polarization tests(PDP)showed a 18%increase in pitting potential and a 76%reduction in corrosion rate after PWHT.The improvement in corrosion resistance is attributed to the increase inΣ3 twin boundaries,which enhance grain boundary stability and reduce susceptibility to localized corrosion.These findings highlight the role of PWHT in refining the microstructure and strengthening corrosion resistance,making HNASS a promising material for demanding applications.展开更多
The microstructure development of 55VNb1 microalloyed steel after warm deformation via multi-pass biaxial compression tests was studied,and the effect of thermomechanical conditions on spheroidisation of cementite lam...The microstructure development of 55VNb1 microalloyed steel after warm deformation via multi-pass biaxial compression tests was studied,and the effect of thermomechanical conditions on spheroidisation of cementite lamellae and ferrite recrystallisation for a range of deformation temperatures(600–700℃),cooling/soaking time(water quenching,air cooling,10 and 30 min of soaking time)and interpass time(0–10 s)was analysed.During deformation,the spheroidisation of pearlite is dynamically accelerated mainly by boundary splitting mechanism together with the rapid dissolution of cementite,while ferrite softening is attributed to dynamic recovery and continuous dynamic recrystallisation.The strong microstructural evolution during cooling/soaking time indicates that deformation energy accumulated is sufficient to activate metallurgical phenomena in both phases also statically.Static spheroidisation is a diffusive process,with rate controlled by the diffusion of vacancies,as suggested by the estimated activation energy.Ferrite refinement is the result of the evolution of continuous recrystallisation and pinning effect exerted by fine,globulised and homogeneously dispersed cementite particles.Increasing temperature causes accelerated kinetics in metallurgical phenomena;therefore,cooling/soaking time becomes key parameters to achieve ultrafine grained and spheroidised microstructures.Interpass time favours spheroidisation and promotes continuous recrystallisation;however,it must be carefully controlled to find a balance between recrystallisation and Ostwald ripening to optimise microstructural development.展开更多
In this study, novel reconstruction methods, including grain graph and variant graph, were established to reconstruct parent austenite on the basis of electron backscatter diffraction (EBSD) data. The evaluation indic...In this study, novel reconstruction methods, including grain graph and variant graph, were established to reconstruct parent austenite on the basis of electron backscatter diffraction (EBSD) data. The evaluation indicators included boundary identification and variant distribution. Moreover, an innovative variant pair analysis method was proposed. The results indicated that the Kurdjumov-Sachs orientation relationship was the most appropriate because it had the smallest refinement error and deviation. In addition, the variant graph reconstruction was more effective in reducing mis-indexing areas than the grain graph, exhibiting a robust capacity to accurately identify austenite grain boundaries. Additionally, the variant graph reconstruction induced the transformation of variants, variant pairs, close-packed plane (CP) groups, and Bain groups. Moreover, various reconstructed datasets (calc-grain data and EBSD data) affected the distribution of variants. The austenite grains reconstructed from the calc-grain data featured two or more variants clustered within the same region due to the preprocessing (calculating, filtering, and smoothing) of the EBSD data. These variations did not impede the microstructural analysis when consistent original data and reconstruction methods were used. The reconstruction of parent austenite grains holds promise for providing a fresh perspective and a deeper understanding of strengthening and toughening mechanisms in the future.展开更多
Employing experimental equipment and techniques,such as electron backscatter diffraction,transmission Kikuchi diffraction,and transmission electron microscopy,the microstructure,phase structure,and orientation relatio...Employing experimental equipment and techniques,such as electron backscatter diffraction,transmission Kikuchi diffraction,and transmission electron microscopy,the microstructure,phase structure,and orientation relationships of 0.6μm electroplated nickel(Ni)steel following annealing at 580-650℃for 15-30 hours were investigated.A comprehensive analysis was conducted to gain insights into the complex changes in the material's properties due to the annealing process.The results reveal that prolonged annealing led to considerable long-range diffusion of surface Ni atoms into the substrate of the 0.6μm Ni-plated steel.This diffusion process resulted in the formation of an alloy diffusion layer,approximately 4μm in thickness,which altered the material's microstructural characteristics.The extent of diffusion and its effect on the microstructure and structure were meticulously quantified.At the annealing temperature,the diffused Ni in the substrate,acting as an austenite-stabilizing element,expanded the austenite phase region.The alloy layer at this temperature predominantly consisted of the face-centered cubic(FCC)-structuredγ(Fe,Ni)solid solution.Upon cooling to room temperature,the alloy diffusion layer evolved into a dual-layer composite structure.The upper layer mainly comprised the FCC-structuredγ(Fe,Ni)solid solution,interspersed with a minor FCC compound superstructure phase.The lower layer underwent a diffusionless phase transformation during cooling,which led to the formation of the body-centered tetragonal/body-centered cubic-structured martensite.This phase,which is known for its high hardness and numerous variants,maintained the classic Kurdjumov-Sachs orientation relationship with the upper FCC parent phase,and it satisfied the close-packed plane{111}γ//{110}α′and close-packed direction<110>γ//<111>α′.A detailed analysis of the different phases within the alloy layer and their phase transitions was presented,offering an in-depth understanding of the material's characteristics.展开更多
Nanoindentation and high resolution electron backscatter diffraction（EBSD） were combined to examine the elastic modulus and hardness of α and β phases,anisotropy in residual elastic stress strain fields and distri...Nanoindentation and high resolution electron backscatter diffraction（EBSD） were combined to examine the elastic modulus and hardness of α and β phases,anisotropy in residual elastic stress strain fields and distributions of geometrically necessary dislocation（GND） density around the indentations within TA15 titanium alloy.The nano-indention tests were conducted on α and β phases,respectively.The residual stress strain fields surrounding the indentation were calculated through crosscorrelation method from recorded patterns.The GND density distribution around the indentation was calculated based on the strain gradient theories to reveal the micro-mechanism of plastic deformation.The results indicate that the elastic modulus and hardness for α p hase are 129.05 GPas and 6.44 GPa,while for β phase,their values are 109.80 GPa and 4.29 GPa,respectively.The residual Mises stress distribution around the indentation is relatively heterogeneous and significantly influenced by neighboring soft β phase.The region with low residual stress around the indentation is accompanied with markedly high a type and prismatic-GND density.展开更多
Grain refinement of AZ31 Mg alloy during cyclic extrusion compression （CEC） at 225-400 ℃ was investigated quantitatively by electron backscattering diffraction （EBSD）. Results show that an ultrafine grained micro...Grain refinement of AZ31 Mg alloy during cyclic extrusion compression （CEC） at 225-400 ℃ was investigated quantitatively by electron backscattering diffraction （EBSD）. Results show that an ultrafine grained microstructure of AZ31 alloy is obtained only after 3 passes of CEC at 225 ℃. The mean misorientation and the fraction of high angle grain boundaries （HAGBs） increase gradually by lowering extrusion temperature. Only a small fraction of {101^-2} twinning is observed by EBSD in AZ31 Mg alloys after 3 passes of CEC. Schmid factors calculation shows that the most active slip system is pyramidal slip {101^-1}〈1120〉and basal slip {0001}〈1120〉 at 225-350 ℃ and 400 ℃, respectively. Direct evidences at subgrain boundaries support the occurrence of continuous dynamic recrystallization （CDRX） mechanism in grain refinement of AZ31 Mg alloy processed by CEC.展开更多
The relation between the Mg treatment and ferrite grain boundaries misorientation was investigated. The orientation imaging microscopy technique based on electron backscattered diffraction technique （EBSD） was used ...The relation between the Mg treatment and ferrite grain boundaries misorientation was investigated. The orientation imaging microscopy technique based on electron backscattered diffraction technique （EBSD） was used in this work. （t was found that the addition of 0.005 wt% Mg to the steel could evidently increase the ratio of acicular ferrite crystals appearing at large angles boundaries to each other, which was attributed to the nucleation of the second-phase particles by the Mg treatment. The FBSD techniques provide a power- ful method to characterize and quantify the ferrite grain boundaries misorientation, in order to relate it to toughness.展开更多
Mechanical properties and texture evolutions of the as-rolled AZ31 Mg sheets were investigated.The results show that the grains of the sheets are significantly refined after hot rolling.The mechanical properties of th...Mechanical properties and texture evolutions of the as-rolled AZ31 Mg sheets were investigated.The results show that the grains of the sheets are significantly refined after hot rolling.The mechanical properties of the as-rolled samples are enhanced due to the grain size refinement.The intensity of basal texture decreases with the increase of deformation ratio,and double-peak type basal texture is discovered in the intermediate and large strain hot rolling processes.The formation of the texture is ascribed to the activities of prismatic and non-basalslips,which is the same as the 30%rolled and 50%rolled samples.The incline of basal planes exerts an effect on the mechanical anisotropy during tension along rolling direction(RD)and transverse direction(TD)at room temperature.展开更多
Thin-walled copper tubes are usually produced by multi-pass float-plug drawing deformation.In general,the annealing treatment subsequently is necessary to release the stored energy and adjusts the microstructure.In th...Thin-walled copper tubes are usually produced by multi-pass float-plug drawing deformation.In general,the annealing treatment subsequently is necessary to release the stored energy and adjusts the microstructure.In this study,an investigation on the evolution of annealing twins as well as textures in the thin-walled(Φ6 mm×0.3 mm)copper tube underwent holding time-free heat treatment was reported.Electron backscattered diffraction analysis reveals that a large number ofΣ3 boundaries(600<111>twin relationship)are produced at the early stage of heat treatment,which is due to the lower boundary energy.With the recrystallization proceeding,the migration rate of grain boundaries decreases on account of the grain growth;meanwhile,the uniqueΣ9 boundaries(38.9°<110>relationship)are formed due to the interaction of theΣ3 boundaries.As a result,the number fractions ofΣ3 boundaries and high-angle grain boundaries decrease rapidly.During the grain growth stage,a strong recrystallization texture was formed due to the fact that the grains of Goss orientation have a growth advantage over the others.As a result,the initial copper texture was transferred into the Goss texture in domination.展开更多
The correlation between microstructures and mechanical properties of a Nb-Ti microalloyed pipeline steel was investigated. The results revealed that with decreasing the finish rolling temperature and the cooling stop ...The correlation between microstructures and mechanical properties of a Nb-Ti microalloyed pipeline steel was investigated. The results revealed that with decreasing the finish rolling temperature and the cooling stop tern perature, the matrix microstructure was changed from quasi-polygonal ferrite to acicular ferrite, as a result of improvement of both strength and low temperature toughness. By means of electron backscattered diffraction observation, an effective acicular ferrite packet contained several low angle boundaries or subboundaries plates which made important contributions to improvement of strength. It was found that many fine quasi-polygonal ferrite grains with high angle boundaries as the toughening structure were introduced into the acicular ferrite matrix to refine effective grain size and improve the toughness.展开更多
The presence ofα/αon priorβ/βgrain boundaries directly impacts the final mechanical properties of the titanium alloys.Theβ/βgrain boundary variant selection of titanium alloys has been assumed to be unlikely owi...The presence ofα/αon priorβ/βgrain boundaries directly impacts the final mechanical properties of the titanium alloys.Theβ/βgrain boundary variant selection of titanium alloys has been assumed to be unlikely owing to the high cooling rates in laser powder bed fusion(L-PBF).However,we hypothesize that powder characteristics such as morphology(non-spherical)and particle size(50–120μm)could affect the initial variant selection in L-PBF processed Ti-6Al-4V alloy by locally altering the cooling rates.Despite the high cooling rate found in L-PBF,results showed the presence ofβ/βgrain boundaryαlath growth inside two adjacent priorβgrains.Electron backscatter diffraction micrographs confirmed the presence ofβ/βgrain boundary variant selection,and synchrotron X-ray high-speed imaging observation revealed the role of the“shadowing effect”on the locally decreased cooling rate because of keyhole depth reduction and the consequentβ/βgrain boundaryαlath growth.The self-accommodation mechanism was the main variant selection driving force,and the most abundantα/αboundary variant was type 4(63.26°//[10553¯]).The dominance of Category IIαlath clusters associated with the type 4α/αboundary variant was validated using the phenomenological theory of martensite transformations and analytical calculations,from which the stress needed for theβ→αtransformation was calculated.展开更多
Strain-induced martensites in high manganese TRIP/TWIP steels were investigated in the presence of thermal martensites and under the influence of austenitic grain orientation by X-ray diffraction （XRD）, scanning ele...Strain-induced martensites in high manganese TRIP/TWIP steels were investigated in the presence of thermal martensites and under the influence of austenitic grain orientation by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and electron backscattered diffraction （EBSD）. Before deformation, the morphology of α＇- M depended mainly on the number of variants and growing period. Regardless of martensite morphologies and deformation, the Kurdjumov-Sachs （K-S） orientation relationships always maintained. The 6 α＇-M variants formed from a plate of ε-M were of 3 pairs of twins with a common axis 〈110〉α＇ parallel to the normal of {112}γ habit plane to minimize transformation strain. When α＇-M could be formed only by deformation, it nucleated at the intersection of ε-M variants and grew mainly in thick ε-M plates. Thick ε plates promoted significantly the α＇-M and weakened the influence of grain orientations. During tension, the transformation in 〈100〉-oriented grains was observed to be slower than that in 〈121〉-oriented grains. Deformation twins promoted ε-M formation slightly and had no apparent effect on α＇-M. Deformation increased the number of ε-M variants, but reduced that of α＇-M variants.展开更多
With the help of FESEM, high resolution electron backscatter diffraction can investigate the grains/subgrains as small as a few tens of nanometers with a good angular resolution （~0.5°）. Fast development of EBS...With the help of FESEM, high resolution electron backscatter diffraction can investigate the grains/subgrains as small as a few tens of nanometers with a good angular resolution （~0.5°）. Fast development of EBSD speed （up to 1100 patterns per second） contributes that the number of published articles related to EBSD has been increasing sharply year by year. This paper reviews the sample preparation, parameters optimization and analysis of EBSD technique, emphasizing on the investigation of ultrafine grained and nanostructured materials processed by severe plastic deformation （SPD）. Detailed and practical parameters of the electropolishing, silica polishing and ion milling have been summarized. It is shown that ion milling is a real universal and promising polishing method for EBSD preparation of almost all materials. There exists a maximum value of indexed points as a function of step size. The optimum step size depends on the magnification and the board resolution/electronic step size. Grains/subgrains and texture, and grain boundary structure are readily obtained by EBSD. Strain and stored energy may be analyzed by EBSD.展开更多
Grain growth inhibitors can effectively suppress the grain size of tungsten carbide(WC),and consequently improve the hardness and strength of the cemented carbides;however,the toughness,one of the most important prope...Grain growth inhibitors can effectively suppress the grain size of tungsten carbide(WC),and consequently improve the hardness and strength of the cemented carbides;however,the toughness,one of the most important properties,usually deteriorates with inhibitors.Here,(Cr,Mo,Ta)_(2)(C,N) synthesized by carbothermal reductionnitridation was used as a novel inhibitor,and its effects on the microstructure and mechanical properties of the cemented carbides were investigated.The results showed that the cemented carbides containing(Cr,Mo,Ta)_(2)(C,N)outperformed its counterpart comprising the traditional inhibitors in comprehensive mechanical properties,which was mainly attributed to the better inhibition performance provided by the(Cr,Mo,Ta)_(2)(C,N) solid-solution powders.With the content of(Cr,Mo,Ta)_(2)(C,N) increasing from 0 wt% to 1.25 wt%,the average grain size of WC in the cemented carbides decreased from 0.85 to 0.60 μm firstly,and then increased to 0.64 μm.With 1.00 wt%(Cr,Mo,-Ta)_(2)(C,N) addition,the cemented carbides with the best performance of hardness(HV_(30)) of 15.55 GPa,transverse rupture strength of 4272 MPa,fracture toughness of13.91 MPa·m1/2 were obtained.The electron backscattered diffraction(EBSD) measurements showed that cemented carbides with(Cr,Mo,Ta)_(2)(C,N) processed more amount of∑2 boundary compared with the other specimens,which contributed to better fracture resistance.展开更多
In this study, shear tests have been performed on the as-reflowed Sn3.5Ag solder bumps and joints to investigate the deformation behavior of Sn3.5Ag lead-free solder samples. Scanning electron microscopy （SEM） was e...In this study, shear tests have been performed on the as-reflowed Sn3.5Ag solder bumps and joints to investigate the deformation behavior of Sn3.5Ag lead-free solder samples. Scanning electron microscopy （SEM） was employed to characterize the microstructures of the samples and orientation imaging microscopy （OIM） with electron backscattered diffraction （EBSD） in SEM was used to obtain crystallographic orientation of grains to provide a detailed characterization of the deformation behavior in Sn3.5Ag solder samples after shear tests. The deformation behavior in solder samples under shear stress was discussed. The experimental results suggest that the dynamic recrystallization could occur under shear stress at room temperature and recrystallized grains should evolve from subgrains by rotation. Compared with that of non-recrystallized and as-reflowed microstructures, the microhardness of the recrystallized microstructure decreased after shear tests.展开更多
基金This work was supported by the National Natural Science Foundation of China under grant No.50171040.
文摘In this paper, the orange peel defect in the surface range of the st14 steel sheet has been investigated using the electron backscattered diffraction (EBSD) technique. It has been found that the orange peel defect in the st14 steel sheet was resulted from the local coarse grains which were produced during hot-rolling due to the critical deformation in dual-phase zone. During deep drawing, the coarse grains with {100}<001> microtexture can slip on the {112}<111> slip system to form bulging and yields orange peel defects, while the coarse grains with {112}<110> orientation do not form the defect as the Schmid factor of {112}<111> slip system in it equals zero.
基金supported by the General Project of Liaoning Provincial Department of Education(NO:JYTMS20231199)Project of Liaoning Education Department(No:LKMZ20220462 and No:LJKMZ20220467)+1 种基金Basic scientific research project of Liaoning Provincial Department of Education(key research project)(No:JYTZD2023108)Liaoning Nature Fund Guidance Plan(No:42022-BS.179)。
文摘In this study,the twinning-detwinning behavior and slip behavior of rolled AZ31 magnesium-alloy plates during a three-step intermittent dynamic compression process along the rolling direction(RD)and normal direction(ND),are investigated via quasi-in situ electron backscatter diffraction,and the causes of the twinning and detwinning behavior are explained according to Schmid law,local strain coordination,and slip trajectories.It is found that the twins are first nucleated and grow at a compressive strain of 3%along the RD.In addition to the Schmid factor(SF),the strain coordination factor(m’)also influences the selection of the twin variants during the twinning process,resulting in the nucleation of twins with a low SF.During the second and third steps of the application of continuous compressive strains with magnitudes and directions of 3%RD+3%ND and 3%RD+3%ND+2.5%ND,detwinning occurs to different extents.The observation of the detwinning behavior reveals that the order in which multiple twins within the same grain undergo complete detwinning is related to Schmid law and the strain concentration,with a low SF and a high strain concentration promoting complete detwinning.The interaction between slip dislocations and twin boundaries in the deformed grains as well as the pinning of dislocations at the tips of the {1012} tensile twins with a special structure result in incomplete detwinning.Understanding the microstructural evolution and twinning behavior of magnesium alloys under different deformation geometries is important for the development of high-strength and high-toughness magnesium alloys.
基金supported by National Natural Science Foundation of China (Grant No. 50864002)Guangxi Provincial Natural Science Foundation of China (Grant No. 0991001)
文摘The Al-Si-Mg alloy which can be strengthened by heat treatment is widely applied to the key components of aerospace and aeronautics. Iron-rich intermetallic compounds are well known to be strongly influential on mechanical properties in Al-Si-Mg alloys. But intermetallic compounds in cast Al-Si-Mg alloy intermetallics are often misidentified in previous metallurgical studies. It was described as many different compounds, such as AlFeSi, Al8Fe2Si, Al5（Fe, Mn）3Si2 and so on. For the purpose of solving this problem, the intermetallic compounds in cast Al-Si alloys containing 0.5% Mg were investigated in this study. The iron-rich compounds in Al-Si-Mg casting alloys were characterized by optical microscope（OM）, scanning electron microscope（SEM）, energy dispersive X-ray spectrometer（EDS）, electron backscatter diffraction（EBSD） and X-ray powder diffraction（XRD）. The electron backscatter diffraction patterns were used to assess the crystallographic characteristics of intermetallic compounds. The compound which contains Fe/Mg-rich particles with coarse morphologies was Al8FeMg3Si6 in the alloy by using EBSD. The compound belongs to hexagonal system, space group P6_2m, with the lattice parameter a=0.662 nm, c=0.792 nm. The β-phase is indexed as tetragonal Al3FeSi2, space group I4/mcm, a=0.607 nm and c=0.950 nm. The XRD data indicate that Al8FeMg3Si6 and Al3FeSi2 are present in the microstructure of Al-7Si-Mg alloy, which confirms the identification result of EBSD. The present study identified the iron-rich compound in Al-Si-Mg alloy, which provides a reliable method to identify the intermetallic compounds in short time in Al-Si-Mg alloy. Study results are helpful for identification of complex compounds in alloys.
基金the financial support of the Ministry of Science and Technology of China (Grant No. 2012CB932201)the National Natural Science Foundation of China (Grant Nos. 51231006 and 51171182)the Danish-Chinese Center for Nanometals (Grant Nos. 51261130091 and DNRF86-5)
文摘An algorithm for grain reconstruction based on electron backscatter diffraction data was proposed in this paper. This algorithm can well record the original data arrangement when an external file for the reconstructed grain（s） was exported for further post-processing. Assisted by an in-house MATLAB program, grain reconstruction, lattice rotations, orientation spreads, and slip system analysis can be performed. The validity of this algorithm has been successfully tested by polycrystalline Ni before and after channel die compression.
文摘Morphology observation and crystallographic analysis of lath martensite in 13Cr-5Ni steel were investigated by electron backscattering diffraction （EBSD） in a scanning electron microscope. The pole figures of the microstructure measured by EBSD showed that the martensite in this steel held the Kurdjumov-Sachs （K-S） orientation relationship, and the boundary misorientations after the austenite-martensite transformation were also analyzed. However, not all the 24 possible variants in the K-S relationship were observed in a single prior austenite grain. Sub-blocks with special combinations were observed, which can be explained by the minimization of the total shape strain between the adjacent variants introduced during the martensite transformation and relatively low carbon content in the 13Cr-5Ni steel.
文摘This study examines the effects of friction stir welding(FSW)and post-weld heat treatment(PWHT)on the grain boundary character distribution and corrosion resistance of cross sectional(top and bottom)regions of nickel-and molybdenum-free high-nitrogen austenitic stainless steel(HNASS).FSW at 400 rpm and 30 mm/min resulted in finer grains(4.18μm)and higher coincident site lattice(CSL)boundaries(32.3%)at the top of the stir zone(SZ)due to dynamic recrystallization(DRX).PWHT at 900℃for 1 h led to grain coarsening(12.91μm the bottom SZ)but enhanced CSL boundaries from 24.6%to 30.2%,improving grain boundary stability.PWHT reduced the kernel average misorientation(KAM)by 14.9%in the SZ-top layer and 20.4%in the SZ-bottom layer,accompanied by a 25%decrease in hardness in the SZ-top layer and 26.7%in the SZ-bottom layer,indicating strain recovery and reduced dislocation density.Potentiodynamic polarization tests(PDP)showed a 18%increase in pitting potential and a 76%reduction in corrosion rate after PWHT.The improvement in corrosion resistance is attributed to the increase inΣ3 twin boundaries,which enhance grain boundary stability and reduce susceptibility to localized corrosion.These findings highlight the role of PWHT in refining the microstructure and strengthening corrosion resistance,making HNASS a promising material for demanding applications.
基金financially supported by the European Coal and Steel Community(RFCS-2015.No.709828).
文摘The microstructure development of 55VNb1 microalloyed steel after warm deformation via multi-pass biaxial compression tests was studied,and the effect of thermomechanical conditions on spheroidisation of cementite lamellae and ferrite recrystallisation for a range of deformation temperatures(600–700℃),cooling/soaking time(water quenching,air cooling,10 and 30 min of soaking time)and interpass time(0–10 s)was analysed.During deformation,the spheroidisation of pearlite is dynamically accelerated mainly by boundary splitting mechanism together with the rapid dissolution of cementite,while ferrite softening is attributed to dynamic recovery and continuous dynamic recrystallisation.The strong microstructural evolution during cooling/soaking time indicates that deformation energy accumulated is sufficient to activate metallurgical phenomena in both phases also statically.Static spheroidisation is a diffusive process,with rate controlled by the diffusion of vacancies,as suggested by the estimated activation energy.Ferrite refinement is the result of the evolution of continuous recrystallisation and pinning effect exerted by fine,globulised and homogeneously dispersed cementite particles.Increasing temperature causes accelerated kinetics in metallurgical phenomena;therefore,cooling/soaking time becomes key parameters to achieve ultrafine grained and spheroidised microstructures.Interpass time favours spheroidisation and promotes continuous recrystallisation;however,it must be carefully controlled to find a balance between recrystallisation and Ostwald ripening to optimise microstructural development.
基金the National Natural Science Foundation of China(Grant Nos.52325406,52374331,and U1960203)the Program of Introducing Talents of Discipline to Universities(Grant No.B21001).
文摘In this study, novel reconstruction methods, including grain graph and variant graph, were established to reconstruct parent austenite on the basis of electron backscatter diffraction (EBSD) data. The evaluation indicators included boundary identification and variant distribution. Moreover, an innovative variant pair analysis method was proposed. The results indicated that the Kurdjumov-Sachs orientation relationship was the most appropriate because it had the smallest refinement error and deviation. In addition, the variant graph reconstruction was more effective in reducing mis-indexing areas than the grain graph, exhibiting a robust capacity to accurately identify austenite grain boundaries. Additionally, the variant graph reconstruction induced the transformation of variants, variant pairs, close-packed plane (CP) groups, and Bain groups. Moreover, various reconstructed datasets (calc-grain data and EBSD data) affected the distribution of variants. The austenite grains reconstructed from the calc-grain data featured two or more variants clustered within the same region due to the preprocessing (calculating, filtering, and smoothing) of the EBSD data. These variations did not impede the microstructural analysis when consistent original data and reconstruction methods were used. The reconstruction of parent austenite grains holds promise for providing a fresh perspective and a deeper understanding of strengthening and toughening mechanisms in the future.
文摘Employing experimental equipment and techniques,such as electron backscatter diffraction,transmission Kikuchi diffraction,and transmission electron microscopy,the microstructure,phase structure,and orientation relationships of 0.6μm electroplated nickel(Ni)steel following annealing at 580-650℃for 15-30 hours were investigated.A comprehensive analysis was conducted to gain insights into the complex changes in the material's properties due to the annealing process.The results reveal that prolonged annealing led to considerable long-range diffusion of surface Ni atoms into the substrate of the 0.6μm Ni-plated steel.This diffusion process resulted in the formation of an alloy diffusion layer,approximately 4μm in thickness,which altered the material's microstructural characteristics.The extent of diffusion and its effect on the microstructure and structure were meticulously quantified.At the annealing temperature,the diffused Ni in the substrate,acting as an austenite-stabilizing element,expanded the austenite phase region.The alloy layer at this temperature predominantly consisted of the face-centered cubic(FCC)-structuredγ(Fe,Ni)solid solution.Upon cooling to room temperature,the alloy diffusion layer evolved into a dual-layer composite structure.The upper layer mainly comprised the FCC-structuredγ(Fe,Ni)solid solution,interspersed with a minor FCC compound superstructure phase.The lower layer underwent a diffusionless phase transformation during cooling,which led to the formation of the body-centered tetragonal/body-centered cubic-structured martensite.This phase,which is known for its high hardness and numerous variants,maintained the classic Kurdjumov-Sachs orientation relationship with the upper FCC parent phase,and it satisfied the close-packed plane{111}γ//{110}α′and close-packed direction<110>γ//<111>α′.A detailed analysis of the different phases within the alloy layer and their phase transitions was presented,offering an in-depth understanding of the material's characteristics.
文摘Nanoindentation and high resolution electron backscatter diffraction（EBSD） were combined to examine the elastic modulus and hardness of α and β phases,anisotropy in residual elastic stress strain fields and distributions of geometrically necessary dislocation（GND） density around the indentations within TA15 titanium alloy.The nano-indention tests were conducted on α and β phases,respectively.The residual stress strain fields surrounding the indentation were calculated through crosscorrelation method from recorded patterns.The GND density distribution around the indentation was calculated based on the strain gradient theories to reveal the micro-mechanism of plastic deformation.The results indicate that the elastic modulus and hardness for α p hase are 129.05 GPas and 6.44 GPa,while for β phase,their values are 109.80 GPa and 4.29 GPa,respectively.The residual Mises stress distribution around the indentation is relatively heterogeneous and significantly influenced by neighboring soft β phase.The region with low residual stress around the indentation is accompanied with markedly high a type and prismatic-GND density.
基金Projects(50674067,51074106,51374145)supported by the National Natural Science Foundation of ChinaProject(09JC1408200)supported by the Science and Technology Commission of Shanghai Municipality,China+1 种基金Project(2011BAE22B01-5)supported by the National Key Technology R&D Program of ChinaProjects(182000/S10,192450/I30)supported by the Research Council of Norway
文摘Grain refinement of AZ31 Mg alloy during cyclic extrusion compression （CEC） at 225-400 ℃ was investigated quantitatively by electron backscattering diffraction （EBSD）. Results show that an ultrafine grained microstructure of AZ31 alloy is obtained only after 3 passes of CEC at 225 ℃. The mean misorientation and the fraction of high angle grain boundaries （HAGBs） increase gradually by lowering extrusion temperature. Only a small fraction of {101^-2} twinning is observed by EBSD in AZ31 Mg alloys after 3 passes of CEC. Schmid factors calculation shows that the most active slip system is pyramidal slip {101^-1}〈1120〉and basal slip {0001}〈1120〉 at 225-350 ℃ and 400 ℃, respectively. Direct evidences at subgrain boundaries support the occurrence of continuous dynamic recrystallization （CDRX） mechanism in grain refinement of AZ31 Mg alloy processed by CEC.
文摘The relation between the Mg treatment and ferrite grain boundaries misorientation was investigated. The orientation imaging microscopy technique based on electron backscattered diffraction technique （EBSD） was used in this work. （t was found that the addition of 0.005 wt% Mg to the steel could evidently increase the ratio of acicular ferrite crystals appearing at large angles boundaries to each other, which was attributed to the nucleation of the second-phase particles by the Mg treatment. The FBSD techniques provide a power- ful method to characterize and quantify the ferrite grain boundaries misorientation, in order to relate it to toughness.
文摘Mechanical properties and texture evolutions of the as-rolled AZ31 Mg sheets were investigated.The results show that the grains of the sheets are significantly refined after hot rolling.The mechanical properties of the as-rolled samples are enhanced due to the grain size refinement.The intensity of basal texture decreases with the increase of deformation ratio,and double-peak type basal texture is discovered in the intermediate and large strain hot rolling processes.The formation of the texture is ascribed to the activities of prismatic and non-basalslips,which is the same as the 30%rolled and 50%rolled samples.The incline of basal planes exerts an effect on the mechanical anisotropy during tension along rolling direction(RD)and transverse direction(TD)at room temperature.
基金financially supported by the Natural Science Foundation of Shandong Province under Grant No.ZR2018MEE005。
文摘Thin-walled copper tubes are usually produced by multi-pass float-plug drawing deformation.In general,the annealing treatment subsequently is necessary to release the stored energy and adjusts the microstructure.In this study,an investigation on the evolution of annealing twins as well as textures in the thin-walled(Φ6 mm×0.3 mm)copper tube underwent holding time-free heat treatment was reported.Electron backscattered diffraction analysis reveals that a large number ofΣ3 boundaries(600<111>twin relationship)are produced at the early stage of heat treatment,which is due to the lower boundary energy.With the recrystallization proceeding,the migration rate of grain boundaries decreases on account of the grain growth;meanwhile,the uniqueΣ9 boundaries(38.9°<110>relationship)are formed due to the interaction of theΣ3 boundaries.As a result,the number fractions ofΣ3 boundaries and high-angle grain boundaries decrease rapidly.During the grain growth stage,a strong recrystallization texture was formed due to the fact that the grains of Goss orientation have a growth advantage over the others.As a result,the initial copper texture was transferred into the Goss texture in domination.
基金Item Sponsored by National Natural Science Foundation of China (51074052)Fundamental Research Funds for Central Universities of China (N100607001)
文摘The correlation between microstructures and mechanical properties of a Nb-Ti microalloyed pipeline steel was investigated. The results revealed that with decreasing the finish rolling temperature and the cooling stop tern perature, the matrix microstructure was changed from quasi-polygonal ferrite to acicular ferrite, as a result of improvement of both strength and low temperature toughness. By means of electron backscattered diffraction observation, an effective acicular ferrite packet contained several low angle boundaries or subboundaries plates which made important contributions to improvement of strength. It was found that many fine quasi-polygonal ferrite grains with high angle boundaries as the toughening structure were introduced into the acicular ferrite matrix to refine effective grain size and improve the toughness.
基金supported in part by the Pennsylvania Infrastructure Technology Alliance,a partnership of Carnegie Mellon,Lehigh University,and the Commonwealth of Pennsylvania’s Department of Community and Economic Development(DCED)The authors recognize Reading Alloys(formerly affiliated with AMETEK Inc.,now a part of Kymera International),especially Muktesh Paliwal and Mike Marucci,for providing the Ti-6Al-4V powder used in this work and for assistance with the study+1 种基金This work was performed under the auspices of the U.S.Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344 and IM release number#LLNL-JRNL-838778The authors acknowledge partial support from the National Science Foundation under grant number DMR-2050916.IG appreciates the financial support from the Gallogly College of Engineering at the University of Oklahoma.
文摘The presence ofα/αon priorβ/βgrain boundaries directly impacts the final mechanical properties of the titanium alloys.Theβ/βgrain boundary variant selection of titanium alloys has been assumed to be unlikely owing to the high cooling rates in laser powder bed fusion(L-PBF).However,we hypothesize that powder characteristics such as morphology(non-spherical)and particle size(50–120μm)could affect the initial variant selection in L-PBF processed Ti-6Al-4V alloy by locally altering the cooling rates.Despite the high cooling rate found in L-PBF,results showed the presence ofβ/βgrain boundaryαlath growth inside two adjacent priorβgrains.Electron backscatter diffraction micrographs confirmed the presence ofβ/βgrain boundary variant selection,and synchrotron X-ray high-speed imaging observation revealed the role of the“shadowing effect”on the locally decreased cooling rate because of keyhole depth reduction and the consequentβ/βgrain boundaryαlath growth.The self-accommodation mechanism was the main variant selection driving force,and the most abundantα/αboundary variant was type 4(63.26°//[10553¯]).The dominance of Category IIαlath clusters associated with the type 4α/αboundary variant was validated using the phenomenological theory of martensite transformations and analytical calculations,from which the stress needed for theβ→αtransformation was calculated.
基金funded by the National Natural Science Foundation of China (No. 50771019)Specialized Research Fund for the Doctoral Program of Higher Education (No. 20090006110013)
文摘Strain-induced martensites in high manganese TRIP/TWIP steels were investigated in the presence of thermal martensites and under the influence of austenitic grain orientation by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and electron backscattered diffraction （EBSD）. Before deformation, the morphology of α＇- M depended mainly on the number of variants and growing period. Regardless of martensite morphologies and deformation, the Kurdjumov-Sachs （K-S） orientation relationships always maintained. The 6 α＇-M variants formed from a plate of ε-M were of 3 pairs of twins with a common axis 〈110〉α＇ parallel to the normal of {112}γ habit plane to minimize transformation strain. When α＇-M could be formed only by deformation, it nucleated at the intersection of ε-M variants and grew mainly in thick ε-M plates. Thick ε plates promoted significantly the α＇-M and weakened the influence of grain orientations. During tension, the transformation in 〈100〉-oriented grains was observed to be slower than that in 〈121〉-oriented grains. Deformation twins promoted ε-M formation slightly and had no apparent effect on α＇-M. Deformation increased the number of ε-M variants, but reduced that of α＇-M variants.
基金Project (192450/I30) supported by the Norwegian Research Council under the Strategic University Program
文摘With the help of FESEM, high resolution electron backscatter diffraction can investigate the grains/subgrains as small as a few tens of nanometers with a good angular resolution （~0.5°）. Fast development of EBSD speed （up to 1100 patterns per second） contributes that the number of published articles related to EBSD has been increasing sharply year by year. This paper reviews the sample preparation, parameters optimization and analysis of EBSD technique, emphasizing on the investigation of ultrafine grained and nanostructured materials processed by severe plastic deformation （SPD）. Detailed and practical parameters of the electropolishing, silica polishing and ion milling have been summarized. It is shown that ion milling is a real universal and promising polishing method for EBSD preparation of almost all materials. There exists a maximum value of indexed points as a function of step size. The optimum step size depends on the magnification and the board resolution/electronic step size. Grains/subgrains and texture, and grain boundary structure are readily obtained by EBSD. Strain and stored energy may be analyzed by EBSD.
基金financially supported by the National Key Research and Development Plan of China(No.2017YFB0305900)the Sichuan Provincial Science Research Program of China(No.2017GZ0120)the Zigong/Sichuan University Science and Technology Cooperation Special Project(No.2018CDZG-14)。
文摘Grain growth inhibitors can effectively suppress the grain size of tungsten carbide(WC),and consequently improve the hardness and strength of the cemented carbides;however,the toughness,one of the most important properties,usually deteriorates with inhibitors.Here,(Cr,Mo,Ta)_(2)(C,N) synthesized by carbothermal reductionnitridation was used as a novel inhibitor,and its effects on the microstructure and mechanical properties of the cemented carbides were investigated.The results showed that the cemented carbides containing(Cr,Mo,Ta)_(2)(C,N)outperformed its counterpart comprising the traditional inhibitors in comprehensive mechanical properties,which was mainly attributed to the better inhibition performance provided by the(Cr,Mo,Ta)_(2)(C,N) solid-solution powders.With the content of(Cr,Mo,Ta)_(2)(C,N) increasing from 0 wt% to 1.25 wt%,the average grain size of WC in the cemented carbides decreased from 0.85 to 0.60 μm firstly,and then increased to 0.64 μm.With 1.00 wt%(Cr,Mo,-Ta)_(2)(C,N) addition,the cemented carbides with the best performance of hardness(HV_(30)) of 15.55 GPa,transverse rupture strength of 4272 MPa,fracture toughness of13.91 MPa·m1/2 were obtained.The electron backscattered diffraction(EBSD) measurements showed that cemented carbides with(Cr,Mo,Ta)_(2)(C,N) processed more amount of∑2 boundary compared with the other specimens,which contributed to better fracture resistance.
基金supported by the National Natural Science Foundation of China under Grant No.50905042the Shenzhen Special Funds for Overseas High-level Talents(No. KQC201109020053A)+1 种基金Shenzhen Technological Innovation Project (No.CXZZ20120829103358067)the Shenzhen Special Funds for Strategic Emerging Industries(No.JCYJ20120613140542764)
文摘In this study, shear tests have been performed on the as-reflowed Sn3.5Ag solder bumps and joints to investigate the deformation behavior of Sn3.5Ag lead-free solder samples. Scanning electron microscopy （SEM） was employed to characterize the microstructures of the samples and orientation imaging microscopy （OIM） with electron backscattered diffraction （EBSD） in SEM was used to obtain crystallographic orientation of grains to provide a detailed characterization of the deformation behavior in Sn3.5Ag solder samples after shear tests. The deformation behavior in solder samples under shear stress was discussed. The experimental results suggest that the dynamic recrystallization could occur under shear stress at room temperature and recrystallized grains should evolve from subgrains by rotation. Compared with that of non-recrystallized and as-reflowed microstructures, the microhardness of the recrystallized microstructure decreased after shear tests.
