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Effects of grain boundary density and dislocation density on formation of adiabatic shear bands in high-strength steel 认领 引用
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作者 Yong-Zheng Yu Yang Zhang +3 位作者 Xing-Hao Li Jun-Peng Li Wei-Guo Jiang Zhong-Wu Zhang 《Journal of Iron and Steel Research International》 SCIE EI CSCD 2026年第5期109-122,共14页
The coupling effect of grain boundary density and dislocation density on the formation mechanism of adiabatic shear band(ASB)during the dynamic failure of high-strength steel was investigated.Though thermomechanical t... The coupling effect of grain boundary density and dislocation density on the formation mechanism of adiabatic shear band(ASB)during the dynamic failure of high-strength steel was investigated.Though thermomechanical treatment,samples with different grain boundary densities(SS:0.67μm-1,1093-SS:0.57μm-1,and 1273-SS:0.24μm-1)and initial dislocation densities(SS:1.3×1015 m-2,1093-SS:8.1×1014m-2,and 1273-SS:5.5×1014m-2)were prepared to elucidate the role of grain boundary density and dislocation density on ASB evolution.Experimental results showed that at a strain rate of 3300 s-1,the high grain boundary density samples(SS and 1093-SS)exhibited higher dynamic flow stresses of 1580 and 1491 MPa,respectively,compared to the low grain boundary density sample of 1273-SS with a stress of 1411 MPa.Under lower dislocation density,the high-density grain boundary network exhibited unique inhibitory effects by preventing dislocation aggregation and entanglement and effectively hindering shear localization,thus significantly delaying dynamic recrystallization.ASB composed of recrystallized grains failed to form due to the significant reduction in the recrystallization ratio.In contrast,low grain boundary density samples exhibited shear localization,leading to the formation of an ASB of approximately 24μm in width.Further studies revealed that at a higher initial dislocation density,dislocation density has a more significant influence on ASB formation compared to grain boundary density.By contrast,the SS sample with high grain boundary density presented an ASB width of 18μm.As a result,findings demonstrate that precise regulation of grain boundary density and dislocation densities enhances the material’s resistance to dynamic recrystallization and effectively suppresses ASB formation while maintaining high flow stress,offering a promising strategy to mitigate dynamic failure in high-strength steels. 展开更多
关键词 High-strength steel Grain boundary density Dislocation density Adiabatic shear band Shear localization
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Electron-induced evolution of dislocation density and morphology in Mg-Y-Nd-Gd-Zr alloy at ultra-low temperature 认领 引用
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作者 Chengqian Huang Zhen Lu +7 位作者 Chao Xu Xiaojun Wang Chengcai Zhang Dekai Liu Bugang Teng Lianmei Wu Fei Li Manman Yi 《Journal of Magnesium and Alloys》 SCIE EI CAS CSCD 2026年第4期118-126,共9页
This study elucidates the non-thermal mechanism of dislocation density reduction in a Mg-Y-Nd-Gd-Zr alloy under continuous electropulsing(6.67-15 A/mm2)at ultra-low temperatures(-150℃ to-196℃)through tripartite c... This study elucidates the non-thermal mechanism of dislocation density reduction in a Mg-Y-Nd-Gd-Zr alloy under continuous electropulsing(6.67-15 A/mm2)at ultra-low temperatures(-150℃ to-196℃)through tripartite characterization and first-principles analysis.Electron backscatter diffraction(EBSD)reveals a 15.2% decrease in geometrically necessary dislocation(GND)density with increasing current,while X-ray line profile analysis(XLPA)confirms the inverse correlation between current intensity and overall defect density.Transmission electron microscopy(TEM)directly visualizes the dissolution of entangled dislocation clusters into isolated lines under high-current treatment(15 A/mm2),corroborating the statistical trends.First-principles calculations demonstrate that localized charge accumulation at defect sites reduces Mg vacancy formation energy by up to 2.8%,lowering lattice resistance to dislocation glide.This charge-state-dependent vacancy proliferation provides a mechanistic link between electron flow and dislocation annihilation.The reduction of vacancy formation energy is a significant factor in the electron-induced dislocation evolution effect at ultra-low temperatures.These findings provide direct evidence for electron-induced dislocation annihilation mechanisms independent of Joule heating,advancing the understanding of electroplasticity in hexagonal close-packed alloys,and providing a novel approach for rapid,non-oxidative microstructural and property tuning of magnesium alloys. 展开更多
关键词 Isolated electric effect Ultra-low temperature Dislocation density and morphology Vacancy formation energy
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A promising approach to enhance fatigue life of TC11 titanium alloy:Low dislocation density and surface grain refinement induced by electropulsing 认领 引用
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作者 Xiuwen Ren Zhongjin Wang Ruidong An 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2025年第1期60-70,共11页
The fatigue life of components can be significantly enhanced by the formation of the surface hardness layer through surface strengthening technology.To avoid the geometric distortion of thin-walled com-ponents caused ... The fatigue life of components can be significantly enhanced by the formation of the surface hardness layer through surface strengthening technology.To avoid the geometric distortion of thin-walled com-ponents caused by strengthening,the strengthening energy is limited and the ideal strengthening effect cannot be obtained.This work aims to propose a novel approach to address this issue effectively.The surface layer with high-density dislocations was obtained by a low-energy surface strengthening method(shot peening)at first.Then the surface strengthening mechanism changes from dislocation strengthen-ing to grain boundary strengthening after electropulsing treatment(EPT).The evolution of residual stress and microstructure was analyzed using multi-scale characterization techniques.The results demonstrate that EPT followed by surface strengthening makes a remarkable 304%increase in fatigue life of TC11 titanium alloy.The enhancement of fatigue life can be attributed to the grain refinement accompanied by the formation of nanotwins and sub-grains in the surface-strengthened layer,as well as the reduction in dislocation density within the substrate after EPT.This study demonstrates the significant potential of EPT in further enhancing the fatigue life of surface pre-strengthened thin-walled components. 展开更多
关键词 Titanium alloy Electropulsing Surface strengthening Fatigue performance Dislocation density Surface grain refinement
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Dislocation density model and microstructure of 7A85 aluminum alloy during thermal deformation 认领 引用 被引量：12
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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(θˉc)increased significantly,ranging from 0.93°to 7.13°.Meanwhile,the fLAGBs 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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Enhancing strength-ductility synergy in a Mg-Gd-Y-Zr alloy at sub-zero temperatures via high dislocation density and shearable precipitates 认领 引用 被引量：8
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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 sufficientdislocations promotes good tensile ductility at−70℃,which is attributed to the minimized critical resolved shear stress(CRSS)ratio of non-basalto 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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The combined influence of grain size distribution and dislocation density on hardness of interstitial free steel 认领 引用 被引量：6
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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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Interface,lattice strain and dislocation density of SiC_p/Al composite consolidated by equal channel angular pressing and torsion 认领 引用 被引量：5
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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-me diate d creep ageing behavior of an Al-Cu-Li alloy 认领 引用 被引量：3
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作者 Chang Zhou Lihua Zhan +1 位作者 Chunhui Liu Minghui Huang 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2024年第7期204-217,共14页
Creep aging is well-known to be a time-dependent,coupled process of deformation and precipitation strengthening for age-hardening alloys.Its existing mechanisms are mainly attributed to those interac-tions between ato... Creep aging is well-known to be a time-dependent,coupled process of deformation and precipitation strengthening for age-hardening alloys.Its existing mechanisms are mainly attributed to those interac-tions between atomic diffusion and dislocation motion.However,an understanding of the relationship between dislocation density and a special multistage creep behavior,i.e.,double steady creep feature,is still far limited.Here we investigate the effect of various dislocation density levels on such an abnormal multistage creep of an Al-Cu-Li alloy.We find that the increased dislocation densities enable an apparent time decrease(from 6.2 h to 0.8 h)of their first steadyⅡ-stage.The yield strength of post-aged sam-ples increases from 425.0 MPa to 580.0 MPa while the corresponding elongation decreases from 12.3%to 7.3%for the creep-aged samples#1 to#4.Microstructural results also reveal that a great difference in dislocation configuration,tailored by various density levels,results in varying creep processes of theⅡ-stage.This stage is closely related to the nucleation and early growth of T1precipitates.Their number densities(maximum:2.9×1019m-3)and the average length(maximum:21.3 nm)of T1precipitates are much smaller than those of the stable peak-aged T1phases,suggesting that creepⅡ-stage of all three creep-aged samples is dominant by the nucleation and initial growth of those T1precipitates.This study provides valuable insights into the dislocation density-mediated creep deformation of an Al-Cu-Li alloy. 展开更多
关键词 Dislocation density Al-Cu-Li alloy Creep ageing T1precipitation
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Relationship between Dislocation Density in P91 Steel and Its Nonlinear Ultrasonic Parameter 认领 引用 被引量：5
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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 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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Anomalous response to creep deformation from dislocation density during electrically assisted creep aging 认领 引用 被引量：1
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作者 Chang Zhou Li-Hua Zhan +1 位作者 Chun-Hui Liu Ming-Hui Huang 《Rare Metals》 SCIE EI CAS CSCD 2024年第10期5268-5283,共16页
Adding numerous dislocations into metallic materials before the forming stage significantly enhances their deformability.However,this beneficial effect of dislocation defects may not have a simple monotonic relationsh... Adding numerous dislocations into metallic materials before the forming stage significantly enhances their deformability.However,this beneficial effect of dislocation defects may not have a simple monotonic relationship with increased dislocation density during electroplastic deformation.This is due to the complex interactions among the drifting electrons,dislocations and solute atoms.This study explores the effect of diverse initial dislocation densities on creep deformation during electrically aided creep aging of an aluminum-lithium alloy.Surprisingly,we discovered a threshold value for the dislocation density that affects electroplastic creep,i.e.,an enhanced effect from dislocations weakens when exceeding this density threshold(an anomalous response to creep).Microstructural data also reveal that such an anomalous response originates mainly from differences in various dislocation density-tailored configurations,which can influence the dislocation motions and precipitation kinetics of the strengthening T1precipitates under the same action of pulsed currents.This study provides important insights into the dislocation density-mediated electroplastic creep of an aluminum-lithium alloy. 展开更多
关键词 Creep aging Dislocation density Al-Cu-Li alloy Pulsed currents
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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 认领 引用 被引量：9
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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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Evaluation of threading dislocation density of strained Ge epitaxial layer by high resolution x-ray diffraction 认领 引用 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 认领 引用 被引量：1
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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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Severe strain localization induced crack suppression in a dislocation-rich FeNiAl high-strength steel 认领 引用
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作者 Weipeng Li Xiedong Sun +2 位作者 Haicheng Zhang Binbin He Chao Jiang 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2026年第7期468-480,共13页
Introducing high dislocation density has proven effective for attaining ultrahigh strength while retaining ductility.However,the role of high dislocation density in affecting the crack initiation and propagation(i.e.,... Introducing high dislocation density has proven effective for attaining ultrahigh strength while retaining ductility.However,the role of high dislocation density in affecting the crack initiation and propagation(i.e.,toughness)is still unclear.The present study investigates the notch fracture behavior and deformation mechanisms of a strong and ductile FeNiAl steel with yield strength of 1797 MPa and uniform elongation of 28.5%,possessing high dislocation density resulting from severe cold-rolling process.The cold rolled steel with high dislocation density exhibits superior crack initiation resistance and fracture energy compared to the annealed counterpart with low dislocation density.Pronounced necking and strain localization are found at notch roots of the cold-rolled sample,indicating enhanced plastic deformation despite its higher yield strength and lower work hardening capacity.The dual roles of high dislocation density are identified:(1)dense dislocation networks restrict dislocation mobility to enhance flow stress while limiting large-range plastic strain under gradient stress;(2)whereas coordinated short-distance slip of abundant dislocations enables intensive and severe plastic strain that suppresses crack nucleation locally,providing critical insights for designing damage-tolerant ultrahigh-strength steels. 展开更多
关键词 High-strength steels High dislocation density Strain localization Ductile fracture Crack initiation resistance
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Achieving springback-free age forming via dislocation-enhanced stress relaxation in Al alloy 认领 引用 被引量：1
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作者 Jianshi Yang Chunhui Liu +2 位作者 Peipei Ma Lihua Zhan Longhui Chen 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 2025年第21期222-238,共17页
Obtaining zero springback and good post-form performance simultaneously is an ultimate pursuit in metal sheet forming.The stress-relaxation ageing(SRA)behavior and mechanical properties of a commercial 2219 aluminum a... Obtaining zero springback and good post-form performance simultaneously is an ultimate pursuit in metal sheet forming.The stress-relaxation ageing(SRA)behavior and mechanical properties of a commercial 2219 aluminum alloy largely pre-deformed(LPD)by 80%have been systematically investigated.The stress relaxation ratio of the LPD alloy reaches approximately 94%regardless of the initial stress(50–350 MPa)after ageing for 12 h at 140°C.This relaxation ratio is about 2.9 and 1.8 times that in the T4 tempered alloy(27.6%under 50 MPa and 31.5%under 150 MPa)and T3 tempered alloy(37.6%under 50 MPa and 51.2%under 150 MPa),respectively.The microstructures,comprised of GP zones/θ'precipitates plus dislocation tangles,and tensile properties in the stress-relaxation-aged LPD alloys remain basically invariant with different initial stresses,as is vital importance for property consistency at different locations of the formed part.Under the same SRA condition,the LPD alloy has an increase of 150–230 MPa in yield strength relative to T3/T4 tempered alloy and obtains a uniform elongation of about 8%.A simple dislocation-based constitutive model accurately describing stress relaxation enhanced by the high dislocation density is established and embedded in the finite element package through a user subroutine.Simulations and experimental verifications show the LPD alloy sheet parts exhibit a nearly zero springback(<5%)after unloading in contrast to the springback larger than 65%in the T3/T4 alloy sheet parts under the same condition.Our findings demonstrate the high-dislocation-density-enhanced SRA response enables a high-performance springback-free age forming of Al alloy sheet. 展开更多
关键词 Age forming Stress relaxation Dislocation density Springback effect Microstructure evolution
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6-inch AlN epitaxial films with low dislocation densities via MOCVD 认领 引用
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作者 Shunpeng Lu Jianwei Ben +8 位作者 Ke Jiang Shanli Zhang Ruojia Zhang Jialong Hao Zhongxu Liu Wenchao Sun Zikai Nie Xiaojuan Sun Dabing Li 《Journal of Semiconductors》 EI CAS CSCD 2025年第2期151-157,共7页
High-quality AlN epitaxial layers with low dislocation densities and uniform crystal quality are essential for next-gener-ation optoelectronic and power devices.This study reports the epitaxial growth of 6-inch AlN fi... High-quality AlN epitaxial layers with low dislocation densities and uniform crystal quality are essential for next-gener-ation optoelectronic and power devices.This study reports the epitaxial growth of 6-inch AlN films on 17 nm AlN/sapphire tem-plates using metal-organic chemical vapor deposition(MOCVD).Comprehensive characterization reveals significant advance-ments in crystal quality and uniformity.Atomic force microscopy(AFM)shows progressive surface roughness reduction during early growth stages,achieving stabilization at a root mean square(RMS)roughness of 0.216 nm within 3 min,confirming suc-cessful 2D growth mode.X-ray rocking curve(XRC)analysis indicates a marked reduction in the(0002)reflection full width at half maximum(FWHM),from 445 to 96 arcsec,evidencing effective dislocation annihilation.Transmission electron microscopy(TEM)demonstrates the elimination of edge dislocations near the AlN template interface.Stress analysis highlights the role of a highly compressive 17 nm AlN template(5.11 GPa)in facilitating threading dislocation bending and annihilation,yielding a final dislocation density of~1.5×107 cm-2.Raman spectroscopy and XRC mapping confirm excellent uniformity of stress and crystal quality across the wafer.These findings demonstrate the feasibility of this method for producing high-quality,large-area,atomically flat AlN films,advancing applications in optoelectronics and power electronics. 展开更多
关键词 AlN 6-inch MOCVD threading dislocation density optoelectronic power electronics
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High density dislocations enhance creep ageing response and mechanical properties in 2195 alloy sheet 认领 引用 被引量：3
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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 1.4×1015m−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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Restraining plastic instability of intercritically annealed 7Mn medium manganese steel via pre-water quenching 认领 引用
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作者 Mei Zhang Wen-Hao Li +6 位作者 Wei-Kun Wang Qing Xu Jie Zhang Qiong-Ying Cen Yang Wang Xiao-Fei Guo Han Dong 《Journal of Iron and Steel Research International》 SCIE EI CSCD 2026年第2期193-208,共16页
The plastic instability and maintaining excellent mechanical properties of 7Mn medium manganese steel(MMnS)were restrained via the inclusion of a pre-water quenching(WQ)step before the traditional intercritical anneal... The plastic instability and maintaining excellent mechanical properties of 7Mn medium manganese steel(MMnS)were restrained via the inclusion of a pre-water quenching(WQ)step before the traditional intercritical annealing(IA)treatment(at 630℃ for 1,2,4 and 8 h).The cold-rolling alloy was austenitized at 850℃ for 0.5 h and then water-quenched to room temperature in advance to adjust the original and final microstructures.The pre-WQ step caused the final ferrite and austenite dual-phase morphology to change from nano-equiaxed to nano-lamellar+equiaxed.The sample after traditional IA at 630℃ for 1 h exhibited excellent comprehensive mechanical properties,with a product of ultimate tensile strength and total elongation(UTS·TEL)of 48.9 GPa%;however,the yield point elongation(YPE)indicating typical plastic instability was as high as 17%.In contrast,the sample after WQ+IA at 630℃ for 4 h showed a similar UTS·TEL of 42.2 GPa%,but the plastic instability phenomena,including the formation of Lüders bands(related to YPE)and Portevin–Le Chatelier bands,were greatly restrained.This was due to the low degree of recrystallization,mixed morphology of the final microstructure,high original dislocation density in ferrite,and fine grain size resulting from pre-WQ.Additionally,the substitution of TEL with positive plasticity(PP=TEL−YPE)allowed a more accurate assessment of the comprehensive properties of MMnS.The as-prepared Lüders-band-free MMnS,with outstanding comprehensive mechanical properties,is of great significance owing to its extensive application potential in the automotive industry. 展开更多
关键词 Medium manganese steel Pre-water quenching Dual-phase morphology Plastic instability High original dislocation density
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Temperature dependence of LiNbO3 dislocation density in the near-surface layer 认领 引用
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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 LiNbO3 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 LiNbO3 depending on thermal annealing in the temperature range of 400℃–600℃.A dynamic model of randomly distributed dislocations has been developed for LiNbO3 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 LiNbO3.The results obtained are important for optical waveguides,LiNbO3-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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Insights into the texture-dependent strain hardening mechanisms of conform-processed AZ31 Mg alloys:Experimental investigations and VPSC modeling 认领 引用
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作者 Yang Mo Jinlong Su +5 位作者 Shudong He Jialin Yang Hang Xu Jie Teng Hui Zhang Fulin Jiang 《Journal of Magnesium and Alloys》 SCIE EI CAS CSCD 2026年第5期452-474,共23页
The texture in magnesium(Mg)alloy affects dislocation nucleation and slip transfer,strain distribution(deformation uniformity),which lead to complex strain hardening behaviors.Basal texture-induced anisotropy has long... The texture in magnesium(Mg)alloy affects dislocation nucleation and slip transfer,strain distribution(deformation uniformity),which lead to complex strain hardening behaviors.Basal texture-induced anisotropy has long limited the formability and strain hardening of Mg alloys.In this work,the Conform process,characterized by intense shear deformation and continuous self-heating,was applied to forge,shear,and recrystallize the grain orientations of an AZ31 Mg alloy.The origins of texture evolution and its roles in strain hardening were investigated by integrating multiscale experiments with visco-plastic self-consistent(VPSC)modeling.The results demonstrated that the pronounced basal texture,together with the bimodal grain size distribution in the as-received alloy,imparted a higher yield strength but constrained its strain-hardening capability.The Conform-processed alloy,with a texture inclination angle of 64°,exhibited a synergistic deformation mode,characterized by stronger basal slip,earlier and sustainedactivity,and increased twin participation that collectively accommodated plastic deformation.This synergy increased dislocation density,with a significant rise in the proportion ofdislocations(from 81.9%to 92.1%)anddislocations(from 18.1%to 40.9%)after Conform processing.These changes in dislocation populations enhanced slip-twin transfer,leading to lower yield strength but improved strain-hardening capacity and tensile ductility.These results demonstrated that Conform process provided an effective strategy for tailoring texture-dependent deformation mechanisms and manufacturing Mg alloys with enhanced strength-ductility synergy. 展开更多
关键词 Mg alloy Continuous extrusion Texture VPSC Slip transfer Dislocation density
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