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Interface,lattice strain and dislocation density of SiC_p/Al composite consolidated by equal channel angular pressing and torsion 被引量:4
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作者 钱陈豪 李萍 薛克敏 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2015年第6期1744-1751,共8页
Powder mixture of pure A1 and oxidized SiC was consolidated into 10% (mass fraction) SiCp/AI composites at 523 K by equal channel angular pressing and torsion (ECAP-T). The interfacial bonding of the composites wa... Powder mixture of pure A1 and oxidized SiC was consolidated into 10% (mass fraction) SiCp/AI composites at 523 K by equal channel angular pressing and torsion (ECAP-T). The interfacial bonding of the composites was characterized by transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). The selected area electron diffraction (SAED) for the interface was investigated. The elements at the interface were scanned by energy dispersive spectroscopy (EDS) and the EDS mapping was also obtained. X-ray diffraction (XRD) analysis was carried out for the composites fabricated by 1 pass, 2 passes and 4 passes ECAP-T. According to the XRD analysis, the influences of ECAP-T pass on the Bragg angle and interplanar spacing for AI crystalline planes were studied. The results show that after ECAP-T, the interface between A1 and SiC within the composites is a belt of amorphous SiO2 containing a trace of A1, Si and C which diffused from the matrix and the reinforcement. With the growing ECAP-T pass, the Bragg angle decreases and interplanar spacing increases for A1 crystalline planes, due to the accumulated lattice strain. The increasing lattice strain of A1 grains also boosts the density of the dislocation within A1 grains. 展开更多
关键词 metal matrix composites severe plastic deformation INTERFACE lattice strain dislocation density
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Dislocation density model and microstructure of 7A85 aluminum alloy during thermal deformation 被引量:7
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作者 HU Jian-liang WU Xiu-jiang +3 位作者 BO Hong JIAO Zi-teng HUANG Shi-quan JIN Miao 《Journal of Central South University》 SCIE EI CAS CSCD 2021年第10期2999-3007,共9页
The microstructure evolution of 7A85 aluminum alloy at the conditions of strain rate(0.001−1 s^(−1))and deformation temperature(250−450°C)was studied by optical microscopy(OM)and electron back scattering diffract... The microstructure evolution of 7A85 aluminum alloy at the conditions of strain rate(0.001−1 s^(−1))and deformation temperature(250−450°C)was studied by optical microscopy(OM)and electron back scattering diffraction(EBSD).Based on the K-M dislocation density model,a two-stage K-M dislocation density model of 7A85 aluminum alloy was established.The results reveal that dynamic recovery(DRV)and dynamic recrystallization(DRX)are the main mechanisms of microstructure evolution during thermal deformation of 7A85 aluminum alloy.350−400°C is the transformation zone from dynamic recovery to dynamic recrystallization.At low temperature(≤350°C),DRV is the main mechanism,while DRX mostly occurs at high temperature(≥400°C).At this point,the sensitivity of microstructure evolution to temperature is relatively high.As the temperature increased,the average misorientation angle(θˉ_(c))increased significantly,ranging from 0.93°to 7.13°.Meanwhile,the f_(LAGBs) decreased with the highest decrease of 24%. 展开更多
关键词 hot deformation microstructure evolution dynamic recrystallization dislocation density model
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Evaluation of threading dislocation density of strained Ge epitaxial layer by high resolution x-ray diffraction 被引量:1
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作者 苗渊浩 胡辉勇 +3 位作者 李鑫 宋建军 宣荣喜 张鹤鸣 《Chinese Physics B》 SCIE EI CAS CSCD 2017年第12期511-515,共5页
The analysis of threading dislocation density (TDD) in Ge-on-Si layer is critical for developing lasers, light emitting diodes (LEDs), photodetectors (PDs), modulators, waveguides, metal oxide semiconductor fiel... The analysis of threading dislocation density (TDD) in Ge-on-Si layer is critical for developing lasers, light emitting diodes (LEDs), photodetectors (PDs), modulators, waveguides, metal oxide semiconductor field effect transistors (MOSFETs), and also the integration of Si-based monolithic photonics. The TDD of Ge epitaxial layer is analyzed by etching or transmission electron microscope (TEM). However, high-resolution x-ray diffraction (HR-XRD) rocking curve provides an optional method to analyze the TDD in Ge layer. The theory model of TDD measurement from rocking curves was first used in zinc-blende semiconductors. In this paper, this method is extended to the case of strained Ge-on-Si layers. The HR-XRD 2θ/ω scan is measured and Ge (004) single crystal rocking curve is utilized to calculate the TDD in strained Ge epitaxial layer. The rocking curve full width at half maximum (FWHM) broadening by incident beam divergence of the instrument, crystal size, and curvature of the crystal specimen is subtracted. The TDDs of samples A and B are calculated to be 1.41108 cm-2 and 6.47108 cm-2, respectively. In addition, we believe the TDDs calculated by this method to be the averaged dislocation density in the Ge epitaxial layer. 展开更多
关键词 HR-XRD RPCVD threading dislocation density (TDD) etching pit density (EPD)
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Microstructure, Dislocation Density and Thermal Expansion Behavior Using Thermo Elastic Models of Zircon Sand Reinforced as Cast ZA-27 Composites
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作者 G. R. Gurunagendra V. Bharat +3 位作者 B. R. Raju D. G. Amith Vijayakumar Pujar C. Ravi Keerthi 《Journal of Minerals and Materials Characterization and Engineering》 2021年第1期100-115,共16页
In the present work stir casting route is used to fabricate the ZA27 Metal matrix composites containing 3 wt%, 6 wt%, 9 wt%, and 12 wt%. Zircon sand particulates of size 100 mesh. Microstructure studies using Optical ... In the present work stir casting route is used to fabricate the ZA27 Metal matrix composites containing 3 wt%, 6 wt%, 9 wt%, and 12 wt%. Zircon sand particulates of size 100 mesh. Microstructure studies using Optical Microscopy, SEM-EDAX are carried out to ascertain the distribution and morphology of particulates in the composites. Effect of zircon sand as reinforcement on bulk density, porosity, of the fabricated composites is studied. SEM studies are carried out to understand the behavior of as-cast ZA27 alloy reinforced with zircon sand. The dislocation density of the fabricated composite affects the strength of the composites and depends on the strain due to thermal mismatch and is found to increase with increase in weight% of zircon sand. However, it does not consider casting defects of voids/clustering observed in micrographs of the fabricated composite. Porosity in composites does not have influence on Coefficient of thermal expansion (CTE) of the ZA27 composites studied using thermoelastic models like Kerner and turner model and rule of mixtures of composite. 展开更多
关键词 density POROSITY dislocation density Thermoelastic Models Rule of Mixtures
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High density dislocations enhance creep ageing response and mechanical properties in 2195 alloy sheet
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作者 WEI Shuo MA Pei-pei +3 位作者 CHEN Long-hui YANG Jian-shi ZHAN Li-hua LIU Chun-hui 《Journal of Central South University》 SCIE EI CAS CSCD 2024年第7期2194-2209,共16页
The creep strain of conventionally treated 2195 alloy is very low,increasing the difficulty of manufacturing Al-Cu-Li alloy sheet parts by creep age forming.Therefore,finding a solution to improve the creep formabilit... The creep strain of conventionally treated 2195 alloy is very low,increasing the difficulty of manufacturing Al-Cu-Li alloy sheet parts by creep age forming.Therefore,finding a solution to improve the creep formability of Al-Cu-Li alloy is vital.A thorough comparison of the effects of cryo-deformation and ambient temperature large pre-deformation(LPD)on the creep ageing response in the 2195 alloy sheet at 160℃with different stresses has been made.The evolution of dislocations and precipitates during creep ageing of LPD alloys are revealed by X-ray diffraction and transmission electron microscopy.High-quality 2195 alloy sheet largely pre-deformed by 80%without edge-cracking is obtained by cryo-rolling at liquid nitrogen temperature,while severe edge-cracking occurs during room temperature rolling.The creep formability and strength of the 2195 alloy are both enhanced by introducing pre-existing dislocations with a density over 1.4×10^(15)m^(−2).At 160℃and 150 MPa,creep strain and creep-aged strength generally increases by 4−6 times and 30−50 MPa in the LPD sample,respectively,compared to conventional T3 alloy counterpart.The elongation of creep-aged LPD sample is low but remains relevant for application.The high-density dislocations,though existing in the form of dislocation tangles,promote the formation of refined T1 precipitates with a uniform dispersion. 展开更多
关键词 creep ageing Al-Cu-Li alloy high dislocation density cryogenic rolling dislocation strengthening
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Enhancing strength-ductility synergy in a Mg-Gd-Y-Zr alloy at sub-zero temperatures via high dislocation density and shearable precipitates 被引量:2
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作者 Xixi Qi Yangxin Li +7 位作者 Xinyu Xu Yuxuan Liu Huan Zhang Qingchun Zhu Gaoming Zhu Jingya Wang Mingxin Huang Xiaoqin Zeng 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2023年第35期123-132,共10页
The strength-ductility trade-offdilemma is hard to be evaded in high-strength Mg alloys at sub-zero temperatures,especially in the Mg alloys containing a high volume fraction of precipitates.In this paper,we report an... The strength-ductility trade-offdilemma is hard to be evaded in high-strength Mg alloys at sub-zero temperatures,especially in the Mg alloys containing a high volume fraction of precipitates.In this paper,we report an enhanced strength-ductility synergy at sub-zero temperatures in an aged Mg-7.37Gd-3.1Y-0.27Zr alloy.The tensile stress-strain curves at room temperature(RT),−70℃ and−196℃ show that the strength increases monotonically with decreasing temperature,but the elongation increases first from RT to−70℃ then declines from−70℃ to−196℃.After systematic investigation of the microstructure evolutions at different deformation temperatures via synchrotron X-ray diffraction,electron backscattered diffraction(EBSD)and transmission electron microscopy(TEM),it is found that a high dislocation density with sufficient<c+a>dislocations promotes good tensile ductility at−70℃,which is attributed to the minimized critical resolved shear stress(CRSS)ratio of non-basal<c+a>to basaldislocations.In ad-dition,more shearable precipitates can further improve the ductility via lengthening the mean free path of dislocation glide.The present work demonstrates that an excellent strength-ductility synergy at sub-zero temperatures can be achieved by introducing a high dislocation density and shearable precipitates in high-strength Mg alloys. 展开更多
关键词 Magnesium alloys Strength-ductility synergy dislocation density Critical resolved shear stress Shearable precipitate
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An iterative blending integrating grinding force model considering grain size and dislocation density evolution
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作者 Zi-Shan Ding Yun-Hui Zhao +3 位作者 Miao-Xian Guo Wei-Cheng Guo Chong-Jun Wu Steven Y.Liang 《Advances in Manufacturing》 SCIE EI CAS CSCD 2023年第3期428-443,共16页
The dynamic force load in grinding process is considered as a crucial factor affecting the quality of parts,and a better understanding of the mechanism of force generation is conducive to revealing the evolution of ma... The dynamic force load in grinding process is considered as a crucial factor affecting the quality of parts,and a better understanding of the mechanism of force generation is conducive to revealing the evolution of material microstructure more precisely.In this study,an iterative blending integrating grinding force model that comprehensively considers the impact of grain size and dislocation density evolution of the material is proposed.According to the grinding kinematics,the interaction of grit-workpiece is divided into rubbing,plowing,and chip formation stages in each grinding zone.On this basis,the evolution of material microstructure in the current chip formation stage will affect the rubbing force in the next grinding arc through flow stresses,which in turn will influence the total grinding force.Therefore,the flow stress models in rubbing and chip formation stages are firstly established,and then the dislocation density prediction model is established experimentally based on the characteristics of grain size.The effects of the evolution of grain size and dislocation density on the grinding forces during the grinding process are studied by means of iterative cycles.The results indicate that the implementation of an iterative blending scheme is instrumental in obtaining a higher accurate prediction of the grinding force and a deeper insight of the influence mechanisms of materials microstructure on grinding process. 展开更多
关键词 Grinding force Grain size dislocation density Iterative loop
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Microstructural evolution,dislocation density and tensile properties of Al–6.5Si–2.1Cu–0.35Mg alloy produced by different casting processes 被引量:2
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作者 S.Samat M.Z.Omar +3 位作者 A.H.Baghdadi I.F.Mohamed A.Rajabi A.M.Aziz 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2021年第36期145-157,共13页
Al–Si–Cu–Mg foundry alloys are used in casting process technologies.However,their strength properties remain low due to their microstructural characteristics and porosity.In this work,the microstructural characteri... Al–Si–Cu–Mg foundry alloys are used in casting process technologies.However,their strength properties remain low due to their microstructural characteristics and porosity.In this work,the microstructural characteristics,dislocation densities,and mechanical properties of Al–Si–Cu–Mg cast alloys prepared through different casting methods were studied experimentally.Four casting processes,namely,gravity casting(GC),rheocasting(RC),thixoforming(Thixo),and Thixo with heat treatment,were used.The GC and RC samples had mainly dendriticα-Al phase microstructures and exhibited coarse Si particles and intermetallic compounds in their interdendritic regions.By contrast,the Thixo and heat-treated Thixo(HT-Thixo)samples exhibited microstructural refinement with uniformly distributedα-Al globules,fine fibrous Si particles,and fragmented intermetallic compounds amongα-Al globules.The accumulation of dislocation densities increased in the Thixo sample as the strain was increased due to plastic deformation.Furthermore,the ultimate tensile strength and yield strength of the HT-Thixo sample increased by 87%and 63%,respectively,relative to those of the GC sample.The cleavage fracture displayed by the GC and RC samples led to brittle failure.Meanwhile,the Thixo and HT-Thixo samples presented dimple-based ductile fracture. 展开更多
关键词 Al–Si–Cu–Mg alloy THIXOFORMING Microstructure Mechanical property dislocation density
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The combined influence of grain size distribution and dislocation density on hardness of interstitial free steel 被引量:1
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作者 Wei Li Martina Vittorietti +1 位作者 Geurt Jongbloed Jilt Sietsma 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2020年第10期35-43,共9页
Understanding the relationship between microstructure features and mechanical properties is of great significance for the improvement and specific adjustment of steel properties.The relationship between mean grain siz... Understanding the relationship between microstructure features and mechanical properties is of great significance for the improvement and specific adjustment of steel properties.The relationship between mean grain size and yield strength is established by the well-known Hall-Petch equation.But due to the complexity of the grain configuration within materials,considering only the mean value is unlikely to give a complete representation of the mechanical behavior.The classical Taylor equation is often used to account for the effect of dislocation density,but not thoroughly tested in combination with grain size influence.In the present study,systematic heat treatment routes and cold rolling followed by annealing are designed for interstitial free(IF)steel to achieve ferritic microstructures that not only vary in mean grain size,but also in grain size distribution and in dislocation density,a combination that is rarely studied in the literature.Optical microscopy is applied to determine the grain size distribution.The dislocation density is determined through XRD measurements.The hardness is analyzed on its relation with the mean grain size,as well as with the grain size distribution and the dislocation density.With the help of the variable selection tool LASSO,it is shown that dislocation density,mean grain size and kurtosis of grain size distribution are the three features which most strongly affect hardness of IF steel. 展开更多
关键词 Interstitial free steel HARDNESS Grain size distribution dislocation density
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Relationship between Dislocation Density in P91 Steel and Its Nonlinear Ultrasonic Parameter 被引量:3
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作者 Ye-qing CAI Jin-zhong SUN +2 位作者 Cheng-jie LIU Shi-wei MA Xi-cheng WEI 《Journal of Iron and Steel Research International》 SCIE EI CAS CSCD 2015年第11期1024-1030,共7页
P91 steel is an important bearing material used in nuclear power plants. The study of its mechanical degradation behavior is important for ensuring safe operation. The relationship between the dislocation density of P... P91 steel is an important bearing material used in nuclear power plants. The study of its mechanical degradation behavior is important for ensuring safe operation. The relationship between the dislocation density of P91 steel under different strains and the corresponding nonlinear ultrasonic parameter β was studied. The dislocation density of strained samples was estimated by X-ray diffraction. Nonlinear ultrasonic testing was conducted to evaluate β, showing that this value increased with increasing dislocation density induced by different tensile elongations. It was shown that the ultrasonic secondharmonic generation technique can effectively evaluate the degradation behavior of metallic materials, and the prediction of the residual life of bearing parts in service can be made based on β and the dislocation density. 展开更多
关键词 dislocation density P91 steel nonlinear ultrasonic second order harmonic
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Temperature dependence of LiNbO3 dislocation density in the near-surface layer
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作者 Oksana Semenova Aleksei Sosunov +1 位作者 Nikolai Prokhorov Roman Ponomarev 《Chinese Optics Letters》 SCIE EI CAS CSCD 2022年第6期40-46,共7页
Density of dislocations in the near-surface layer was investigated in X-cut LiNbO_(3) depending on thermal annealing in the temperature range of 400℃–600℃.A dynamic model of randomly distributed dislocations has be... Density of dislocations in the near-surface layer was investigated in X-cut LiNbO_(3) depending on thermal annealing in the temperature range of 400℃–600℃.A dynamic model of randomly distributed dislocations has been developed for LiNbO_(3) by using X-ray diffraction.The experimental results showed that the dislocation density of the near-surface layer reached the minimum at the thermal annealing temperature of 500℃,with the analysis being performed when wet selective etching and X-ray diffraction methods were used.We concluded that homogenization annealing is an effective technique to improve the quality of photonic circuits based on LiNbO_(3).The results obtained are important for optical waveguides,LiNbO_(3)-on-insulator-based micro-photonic devices,electro-optical modulators,sensors,etc. 展开更多
关键词 lithium niobate etching pits near-surface layer density of dislocations annealing X-ray diffraction
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In-situ study of the microstructure evolution during tension of a Mg-Y-Zn-Al alloy processed by rapidly solidified ribbon consolidation technique
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作者 Jeno Gubicza Kristián Máthis +7 位作者 Péter Nagy Péter Jenei Zoltán Hegedus Andrea Farkas Jozef Vesely Shin-ichi Inoue Daria Drozdenko Yoshihito Kawamura 《Journal of Magnesium and Alloys》 SCIE EI CAS CSCD 2024年第5期2024-2040,共17页
Mg-Y-Zn-Al alloys processed by rapidly solidified ribbon consolidation(RSRC)technique exhibit an exceptional mechanical performance indicating promising application potential.This material has a bimodal microstructure... Mg-Y-Zn-Al alloys processed by rapidly solidified ribbon consolidation(RSRC)technique exhibit an exceptional mechanical performance indicating promising application potential.This material has a bimodal microstructure consisting of fine recrystallized and coarse non-recrystallized grains with solute-rich stacking faults forming cluster arranged layers(CALs)and nanoplates(CANaPs),or complete long period stacking ordered(LPSO)phase.In order to reveal the deformation mechanisms,in-situ synchrotron X-ray diffraction line profile analysis was employed for a detailed study of the dislocation arrangement created during tension in Mg-0.9%Zn-2.05%Y-0.15%Al(at%)alloy.For uncovering the effect of the initial microstructure on the mechanical performance,additional samples were obtained by annealing of the as-consolidated specimen at 300 and 400℃ for 2 h.The heat treatment at 300℃ had no significant effect on the initial microstructure,its evolution during tension and,thus,the overall deformation behavior under tensile loading.On the other hand,annealing at 400℃ resulted in a significant increase of the recrystallized grains fraction and a decrease of the dislocation density,leading to only minor degradation of the mechanical strength.The maximum dislocation density at the failure of the samples corresponding to the plastic strain of 10-25% was estimated to be about 16-20×10^(14)m^(-2).The diffraction profile analysis indicated that most dislocations formed during tension were of non-basal and pyramidal types,what was also in agreement with the Schmid factor values revealed independently from orientation maps.It was also shown that the dislocation-induced Taylor hardening was much lower below the plastic strain of 3% than above this value,which was explained by a model of the interaction between prismatic dislocations and CANaPs/LPSO plates. 展开更多
关键词 Mg-Zn-Y-Al alloy Long period stacking ordered(LPSO)phase Cluster arranged nanoplates(CANaPs) Annealing Tension dislocation density Hardening
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Effect of dislocation structure evolution on low-angle grain boundary formation in 7050 aluminum alloy during aging
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作者 Wei Gu Jing-yuan Li Yi-de Wang 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CAS CSCD 2015年第7期721-728,共8页
The effect of dislocation structure evolution on low-angle grain boundary formation in 7050 aluminum alloy during aging was studied by using optical microscopy, transmission electron microscopy, and electron backscatt... The effect of dislocation structure evolution on low-angle grain boundary formation in 7050 aluminum alloy during aging was studied by using optical microscopy, transmission electron microscopy, and electron backscatter diffraction analysis of misorientation angle distribution, cumulative misorientation and geometrically necessary dislocation (GND) density. Experimental results indicate that coarse spindle-shaped grains with the dimension of 200 μm- 80 μm separate into fine equiaxed grains of 20μm in size as a result of newborn low-angle grain boundaries formed during the aging process. More specifically, the dislocation arrays, which are rearranged and formed due to scattered dislocations during earlier quenching, transform into low-angle grain boundaries with aging time. The relative frequency of 3°-5° low-angle grain boundaries increases to over 30%. The GND density, which describes low-angle grain boundaries with the misorientation angle under 3°, tends to decrease during initial aging. The inhomogeneous distribution of GNDs is affected by grain orientation. A decrease in GND density mainly occurs from 1.83 × 10^13 to 4.40 × 10^11 m^-2 in grains with 〈111〉 fiber texture. This is consistent with a decrease of unit cumulative misorientation. Precipitation on grain boundaries and the formation of a precipitation free zone (PFZ) are facilitated due to the eroding activity of the Graft etchant. Consequently, low-angle grain boundaries could be readily viewed by optical microscopy due to an increase in their electric potential difference. 展开更多
关键词 aluminum alloys low-angle grain boundaries dislocation structure AGING dislocation density
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Dislocation characteristics and dynamic recrystallization in hot deformed AM30 and AZ31 alloys
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作者 Hyeon-Woo Son Soong-Keun Hyun 《Journal of Magnesium and Alloys》 SCIE EI CAS CSCD 2022年第12期3495-3505,共11页
Zn addition to Mg alloys activates non-basal slip or twinning with solute softening effects.On the other hand,the effects of the Zn solute on the macroscopic dislocation behavior and dynamic recrystallization are not ... Zn addition to Mg alloys activates non-basal slip or twinning with solute softening effects.On the other hand,the effects of the Zn solute on the macroscopic dislocation behavior and dynamic recrystallization are not completely understood.Moreover,it is unclear ifslip can be affected by changes in the c/a ratio of solute atoms.This study was conducted to understand the solute strengthening of Zn addition and its effects on the dislocation characteristics and dynamic recrystallization.A hot torsion test was performed on both AM30 and AZ31 alloys up to a high strain to investigate the Zn solute effect on the dislocation characteristics and dynamic recrystallization.The dislocation components of the hot torsioned alloys were evaluated by X-ray line profile analysis and electron backscatter diffraction.The results showed that the Zn solutes slightly accelerate strain accumulation at the initial stages of hot deformation,which accelerated recrystallization at high strain.The dislocation characteristics were changed dynamically by Zn addition:fortified-type slip,dislocation arrangement and strain anisotropy parameters.The most important point was that the dislocation characteristics were changed dramatically at the critical strain for recrystallization and high strain regions.The addition of Zn also acted greatly in these strain areas.This indicates that the rapid formation of-type slip at the serrated grain boundaries occurs at the initiation of dynamic recrystallization and the increase in the grain triple junction because grain refinement has a great influence on the dislocation characteristics at high strain. 展开更多
关键词 Magnesium alloy X-ray line profile Solid solution dislocation density Dynamic recrystallization
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The effect of dislocations on the thermodynamic properties of Ta single crystal under high pressure by molecular dynamics simulation
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作者 Yalin Li Jun Cai +1 位作者 Dan Mo Yandong Wang 《Chinese Physics B》 SCIE EI CAS CSCD 2018年第8期434-438,共5页
The thermodynamic properties of Ta metal under high pressure are studied by molecular dynamics simulation. For dislocation-free Ta crystal, all the thermodynamic properties considered are in good agreement with the re... The thermodynamic properties of Ta metal under high pressure are studied by molecular dynamics simulation. For dislocation-free Ta crystal, all the thermodynamic properties considered are in good agreement with the results from exper- iments or higher level calculations. If dislocations are included in the Ta crystal, it is found that as the dislocation density increases, the hydrostatic pressure at the phase transition point of bcc-+hcp and hcp--+fcc decreases, while the Hugoniot temperature increases. Meanwhile, the impact pressure at the elastic-plastic transition point is found to depend on the crys- tallographic orientation of the pressure. As the dislocation density increases, the pressure of the elastic-plastic transition point decreases rapidly at the initial stage, then gradually decreases with the increase of the dislocation density. 展开更多
关键词 Ta high pressure phase transition dislocation density molecular dynamics (MD)
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A simple model for diffusion-induced dislocations during the lithiation of crystalline materials
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作者 Fuqian Yang 《Theoretical & Applied Mechanics Letters》 CAS 2014年第5期9-12,共4页
Assuming that the lithiation reaction occurs randomly in individual small particles in the vicinity of the reaction front, a simple model of diffusion- induced dislocations was developed. The diffusion-induced disloca... Assuming that the lithiation reaction occurs randomly in individual small particles in the vicinity of the reaction front, a simple model of diffusion- induced dislocations was developed. The diffusion-induced dislocations are con- trolled by the misfit strain created by the diffusion of solute atoms or the phase transformation in the vicinity of the reaction front. The dislocation density is proportional to the total surface area of the "lithiated particle" and inversely pro- portional to the particle volume. The diffusion-induced dislocations relieve the diffusion-induced stresses. 展开更多
关键词 DIFFUSION misfit strain dislocation density LITHIATION
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Pitting corrosion behavior and corrosion protection performance of cold sprayed double layered noble barrier coating on magnesium-based alloy in chloride containing solutions
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作者 M.Daroonparvar A.Helmer +7 位作者 A.M.Ralls M.U.Farooq Khan A.K.Kasar R.K.Gupta M.Misra S.Shao P.L.Menezes N.Shamsaei 《Journal of Magnesium and Alloys》 SCIE EI CAS CSCD 2023年第9期3099-3119,共21页
Nitrogen processed, cold sprayed commercially pure(CP)-Al coatings on Mg-based alloys mostly lack acceptable hardness, wear resistance and most importantly are highly susceptible to localized corrosion in chloride con... Nitrogen processed, cold sprayed commercially pure(CP)-Al coatings on Mg-based alloys mostly lack acceptable hardness, wear resistance and most importantly are highly susceptible to localized corrosion in chloride containing solutions. In this research, commercially pure α-Ti top coating having good pitting potential(~1293 mV_(SCE)), high microhardness(HV_(0.025): 263.03) and low wear rate was applied on a CP-Al coated Mg-based alloy using high pressure cold spray technology. Potentiodynamic polarization(PDP) curves indicated that the probability of transition from metastable pits to the stable pits for cold spayed(CS) Al coating is considerably higher compared to that with the CS Ti top coating(for Ti/Al/Mg system). In addition, CS Ti top coating was in the passivation region in most pH ranges even after 48 h immersion in 3.5 wt% NaCl solution. The stored energy in the CS Ti top coating(as a passive metal) was presumed to be responsible for the easy passivation. Immersion tests indicated no obvious pits formation on the intact CS Ti top coating surface and revealed effective corrosion protection performance of the CS double layered noble barrier coatings on Mg alloys in 3.5 wt% NaCl solution even after 264 h. 展开更多
关键词 Ti coating Mg alloys Localized corrosion PASSIVITY dislocation density Crystallite size
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Solute drag-controlled grain growth in magnesium investigated by quasi in-situ orientation mapping and level-set simulations
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作者 Risheng Pei Yujun Zhao +2 位作者 Muhammad Zubair Sangbong Yi Talal Al-Samman 《Journal of Magnesium and Alloys》 SCIE EI CAS CSCD 2023年第7期2312-2325,共14页
Critical properties of metallic materials,such as the yield stress,corrosion resistance and ductility depend on the microstructure and its grain size and size distribution.Solute atoms that favorably segregate to grai... Critical properties of metallic materials,such as the yield stress,corrosion resistance and ductility depend on the microstructure and its grain size and size distribution.Solute atoms that favorably segregate to grain boundaries produce a pinning atmosphere that exerts a drag pressure on the boundary motion,which strongly affects the grain growth behavior during annealing.In the current work,the characteristics of grain growth in an annealed Mg-1 wt.%Mn-1 wt.%Nd magnesium alloy were investigated by advanced experimental and modeling techniques.Systematic quasi in-situ orientation mappings with a scanning electron microscope were performed to track the evolution of local and global microstructural characteristics as a function of annealing time.Solute segregation at targeted grain boundaries was measured using three-dimensional atom probe tomography.Level-set computer simulations were carried with different setups of driving forces to explore their contribution to the microstructure development with and without solute drag.The results showed that the favorable growth advantage for some grains leading to a transient stage of abnormal grain growth is controlled by several drivers with varying importance at different stages of annealing.For longer annealing times,residual dislocation density gradients between large and smaller grains are no longer important,which leads to microstructure stability due to predominant solute drag.Local fluctuations in residual dislocation energy and solute concentration near grain boundaries cause different boundary segments to migrate at different rates,which affects the average growth rate of large grains and their evolved shape. 展开更多
关键词 Magnesium alloys Grain growth Quasi in-situ EBSD Level-set simulation Solute drag dislocation density gradient
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Simulated and experimental investigation on discontinuous dynamic recrystallization of a near-α TA15 titanium alloy during isothermal hot compression in βsingle-phase field 被引量:5
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作者 武川 杨合 李宏伟 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2014年第6期1819-1829,共11页
A cellular automaton(CA) modeling of discontinuous dynamic recrystallization(DDRX) of a near-α Ti-6Al-2Zr-1Mo-1V(TA15) isothermally compressed in the β single phase field was presented.In the CA model,nucleati... A cellular automaton(CA) modeling of discontinuous dynamic recrystallization(DDRX) of a near-α Ti-6Al-2Zr-1Mo-1V(TA15) isothermally compressed in the β single phase field was presented.In the CA model,nucleation of the β-DDRX and the growth of recrystallized grains(re-grains) were considered and visibly simulated by the CA model.The driving force of re-grain growth was provided by dislocation density accumulating around the grain boundaries.To verify the CA model,the predicted flow stress by the CA model was compared with the experimental data.The comparison showed that the average relative errors were10.2%,10.1%and 6%,respectively,at 1.0,0.1 and 0.01 s^-1 of 1020 ℃,and were 10.2%,11.35%and 7.5%,respectively,at 1.0,0.1and 0.01 s^-1 of 1050 ℃.The CA model was further applied to predicting the average growth rate,average re-grain size and recrystallization kinetics.The simulated results showed that the average growth rate increases with the increasing strain rate or temperature,while the re-grain size increases with the decreasing strain rate;the volume fraction of recrystallization decreases with the increasing strain rate or decreasing temperature. 展开更多
关键词 discontinuous dynamic recrystallization cellular automaton dislocation density evolution recrystallization kinetics TA15 titanium alloy
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Effect of thermal annealing on defects of upgraded metallurgical grade silicon 被引量:3
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作者 吴洪军 马文会 +4 位作者 陈秀华 蒋咏 梅向阳 张聪 吴兴惠 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2011年第6期1340-1347,共8页
Effect of thermal annealing on the upgraded metallurgical grade(UMG)-Si was investigated under different conditions.The dislocation,grain boundaries and preferred growth orientation of Si ingot were characterized by... Effect of thermal annealing on the upgraded metallurgical grade(UMG)-Si was investigated under different conditions.The dislocation,grain boundaries and preferred growth orientation of Si ingot were characterized by optical microscopy,electron back scattering diffraction(EBSD) and X-ray diffractometry(XRD),respectively.The arrange order of dislocation density of Si ingot is from the lowest in the middle to the lower in the bottom and low in the top before and after annealing.And it decreases gradually with increase of the annealing temperature.The number of small angle grain boundaries declines gradually until disappears whereas the proportion of coincidence site lattice(CSL) grain boundaries increases firstly and then decreases.The twin boundary Σ3 reaches the highest proportion of 28% after annealing at 1 200 ℃ for 3 h.Furthermore,the crystal grains in different positions gain the best preferred growth orientation,which can promote the following machining of Si ingot and the conversion efficiency of solar cells. 展开更多
关键词 upgraded metallurgical grade(UMG-Si) ANNEALING dislocation density grain boundaries
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