Grain boundary(GB)deformation and twinning behavior have been recognized as important contributors to the plasticity of polycrystalline materials.However,a comprehensive understanding of dynamic interplay between GB d...Grain boundary(GB)deformation and twinning behavior have been recognized as important contributors to the plasticity of polycrystalline materials.However,a comprehensive understanding of dynamic interplay between GB deformation and twinning behavior remains largely elusive.Using in situ nanomechanical testing,we reveal that GB plasticity and twinning plasticity can be strongly coupled in the context of various deformation characteristics,including lamellae-type twinning from GBs,GB splitting-induced twinning,twinning from triple junctions(TJs),and GB-mediated hierarchical twinning.These GB/TJ-associated twinning modes often arise from the combined effect of macroscopic(geometry-dominated)and microscopic(excess volume-dominated)degrees of freedom of GBs/TJs as an effective way to alleviate local stress concentration,which in turn provides a chance of adjusting GB mobility and enhancing the coordinated evolution of entire interface network in three-dimensional space.Such coupling between GB plasticity and twinning plasticity should represent a general deformation mode in different metallic materials,holding important implications for preventing premature GB cracking and enhancing material ductility.展开更多
The authors regret for the missing of copyright attributions in the captions of Fig.1(d)and Fig.7 in the original publication.Please note the corrections do not affect the experimental results and conclusions.In the o...The authors regret for the missing of copyright attributions in the captions of Fig.1(d)and Fig.7 in the original publication.Please note the corrections do not affect the experimental results and conclusions.In the originally published article,Fig.1(d)and Fig.7 were adapted from previously published figures in the cited literature.展开更多
Grain boundary(GB)mediated deformation is a vital contributor to the plasticity of polycrystalline materials,where the disconnection model has become a widely recognized approach to depict the GB dynamics.However,expe...Grain boundary(GB)mediated deformation is a vital contributor to the plasticity of polycrystalline materials,where the disconnection model has become a widely recognized approach to depict the GB dynamics.However,experimental understanding of the atomistic disconnection dynamics remains scarce.In this case study of gold nanocrystals,atomistic disconnection dynamics governing the shear-coupled migration of flat GBs have been systematically investigated via in situ transmission electron microscopy nanomechanical testing supported by molecular dynamics simulations.Specifically,the site-dependent nucleation,shear-driven propagation,and diverse interactions associated with distinct GB disconnections are systematically elucidated and quantitatively compared.Moreover,the disconnection-mediated GB plasticity proves to prevail among different tilt and mixed GBs in gold.Eventually,a conceptual map of disconnection-mediated GB dynamics is established,which would furnish a unified understanding of GB plasticity in metallic materials.展开更多
Grain growth and shrinkage are essential to the thermal and mechanical stability of nanocrystalline metals,which are assumed to be governed by the coordinated deformation between neighboring grain boundaries(GBs)in th...Grain growth and shrinkage are essential to the thermal and mechanical stability of nanocrystalline metals,which are assumed to be governed by the coordinated deformation between neighboring grain boundaries(GBs)in the nanosized grains.However,the dynamics of such coordination has rarely been reported,especially in experiments.In this work,we systematically investigate the atomistic mechanism of coordinated GB deformation during grain shrinkage in an Au nanocrystal film through combined stateof-the-art in situ shear testing and atomistic simulations.We demonstrate that an embedded nanograin experiences shrinkage and eventually annihilation during a typical shear loading cycle.The continuous grain shrinkage is accommodated by the coordinated evolution of the surrounding GB network via dislocation-mediated migration,while the final grain annihilation proceeds through the sequential dislocation-annihilation-induced grain rotation and merging of opposite GBs.Both experiments and simulations show that stress distribution and GB structure play important roles in the coordinated deformation of different GBs and control the grain shrinkage/annihilation under shear loading.Our findings establish a mechanistic relation between coordinated GB deformation and grain shrinkage,which reveals a general deformation phenomenon in nanocrystalline metals and enriches our understanding on the atomistic origin of structural stability in nanocrystalline metals under mechanical loading.展开更多
The Zhongjiang gas field is a typical large gas field in terrigenous strata of the Western Sichuan Depression.It remains debatable which member of the Upper Triassic Xujiahe Formation served as the source rocks and ho...The Zhongjiang gas field is a typical large gas field in terrigenous strata of the Western Sichuan Depression.It remains debatable which member of the Upper Triassic Xujiahe Formation served as the source rocks and how significant the member contributed to the gas accumulations in the Zhongjiang gas field.In this study,we analyzed the essential characteristics of the Lower Jurassic source rocks and the geochemical features of light hydrocarbons in natural gas from the 2nd(T_(3)χ^(2))and 4th members(T_(3)χ^(4))of the Upper Triassic Xujiahe Formation(T_(3)χ),as well as the Middle Jurassic Shaximiao(J_(2)s)and Qianfoya(J_(2)q)formations.Based on this,we explored the sources of the natural gas in the Zhongjiang gas field and determined the natural gas migration patterns and their effects on the properties of light hydrocarbons in the natural gas.The results indicate that the Lower Jurassic lacustrine source rocks of the Zhongjiang gas field contain humic organic matter,with vitrinite reflectance(R_(0))values ranging from 0.86%to 0.98%.Samples meeting the criterion for effective source rocks[total organic carbon(TOC)content≥0.75%]exhibited an average TOC content of merely 1.02%,suggesting significantly lower hydrocarbon generation potential than source rocks in the underlying T3x,which show higher thermal maturity and TOC contents.For natural gas samples from T_(3)χ^(2),T_(3)χ^(4),J_(2)s,and J_(2)q reservoirs,their C_(5-7)iso-alkane content was significantly higher than their n-alkane content,and their methylcyclohexane(MCH)index ranged from 59.0%to 77.3%,indicating the predominance of methylcyclohexane in C_(7)light hydrocarbons.As indicated by the origin identification and gas-source correlation based on the geochemical features of light hydrocarbons,the natural gas in the Zhongjiang gas field is typical coal-derived gas.The gas from the primary pay zone of the Shaximiao Formation,with significantly high K_(1),(P_(2)+N_(2))/C_(7),and P_(3)/C_(7)values,predominantly originated from the 5th member of the T3x and migrated in the free phase,with a small amount possibly sourced from the Lower Jurassic source rocks.The dissolution and adsorption during gas migration led to a decrease in the aromatic content in C_(6-7)light hydrocarbons and an increase in the isoheptane values.Therefore,their effects must be considered when determining the gas origin and thermal maturity based on the aromatic content in C_(6-7) light hydrocarbons and iso-heptane values.展开更多
基金financially supported by the National Key R&D Program of China(No.2021YFA1200201)the National Natural Science Foundation of China(No.52071284)the Zhejiang Provincial Natural Science Foundation of China(No.LR24E010002).
文摘Grain boundary(GB)deformation and twinning behavior have been recognized as important contributors to the plasticity of polycrystalline materials.However,a comprehensive understanding of dynamic interplay between GB deformation and twinning behavior remains largely elusive.Using in situ nanomechanical testing,we reveal that GB plasticity and twinning plasticity can be strongly coupled in the context of various deformation characteristics,including lamellae-type twinning from GBs,GB splitting-induced twinning,twinning from triple junctions(TJs),and GB-mediated hierarchical twinning.These GB/TJ-associated twinning modes often arise from the combined effect of macroscopic(geometry-dominated)and microscopic(excess volume-dominated)degrees of freedom of GBs/TJs as an effective way to alleviate local stress concentration,which in turn provides a chance of adjusting GB mobility and enhancing the coordinated evolution of entire interface network in three-dimensional space.Such coupling between GB plasticity and twinning plasticity should represent a general deformation mode in different metallic materials,holding important implications for preventing premature GB cracking and enhancing material ductility.
文摘The authors regret for the missing of copyright attributions in the captions of Fig.1(d)and Fig.7 in the original publication.Please note the corrections do not affect the experimental results and conclusions.In the originally published article,Fig.1(d)and Fig.7 were adapted from previously published figures in the cited literature.
基金support of the National Key R&D Program of China(No.2021YFA1200201)the National Natural Science Foundation of China(Nos.52071284 and 51771172)support from NSERC Discovery grant(No.RGPIN-05834-2019)。
文摘Grain boundary(GB)mediated deformation is a vital contributor to the plasticity of polycrystalline materials,where the disconnection model has become a widely recognized approach to depict the GB dynamics.However,experimental understanding of the atomistic disconnection dynamics remains scarce.In this case study of gold nanocrystals,atomistic disconnection dynamics governing the shear-coupled migration of flat GBs have been systematically investigated via in situ transmission electron microscopy nanomechanical testing supported by molecular dynamics simulations.Specifically,the site-dependent nucleation,shear-driven propagation,and diverse interactions associated with distinct GB disconnections are systematically elucidated and quantitatively compared.Moreover,the disconnection-mediated GB plasticity proves to prevail among different tilt and mixed GBs in gold.Eventually,a conceptual map of disconnection-mediated GB dynamics is established,which would furnish a unified understanding of GB plasticity in metallic materials.
基金supports of the National Key Research and Development Program of China(No.2018YFB2000704)the National Natural Science Foundation of China(51771172 and 52071284)+2 种基金the Innovation Fund of the Zhejiang Kechuang New Materials Research Institute(ZKN-18-Z02)financial support from the National Natural Science Foundation of China(11902289)computational support from the Super Cloud Computing Center in Beijing。
文摘Grain growth and shrinkage are essential to the thermal and mechanical stability of nanocrystalline metals,which are assumed to be governed by the coordinated deformation between neighboring grain boundaries(GBs)in the nanosized grains.However,the dynamics of such coordination has rarely been reported,especially in experiments.In this work,we systematically investigate the atomistic mechanism of coordinated GB deformation during grain shrinkage in an Au nanocrystal film through combined stateof-the-art in situ shear testing and atomistic simulations.We demonstrate that an embedded nanograin experiences shrinkage and eventually annihilation during a typical shear loading cycle.The continuous grain shrinkage is accommodated by the coordinated evolution of the surrounding GB network via dislocation-mediated migration,while the final grain annihilation proceeds through the sequential dislocation-annihilation-induced grain rotation and merging of opposite GBs.Both experiments and simulations show that stress distribution and GB structure play important roles in the coordinated deformation of different GBs and control the grain shrinkage/annihilation under shear loading.Our findings establish a mechanistic relation between coordinated GB deformation and grain shrinkage,which reveals a general deformation phenomenon in nanocrystalline metals and enriches our understanding on the atomistic origin of structural stability in nanocrystalline metals under mechanical loading.
基金funded by the National Natural Science Foundation of China(No.42172149,No.U2244209)the SINOPEC Science and Technology Project(No.P22132,No.P21077-1).
文摘The Zhongjiang gas field is a typical large gas field in terrigenous strata of the Western Sichuan Depression.It remains debatable which member of the Upper Triassic Xujiahe Formation served as the source rocks and how significant the member contributed to the gas accumulations in the Zhongjiang gas field.In this study,we analyzed the essential characteristics of the Lower Jurassic source rocks and the geochemical features of light hydrocarbons in natural gas from the 2nd(T_(3)χ^(2))and 4th members(T_(3)χ^(4))of the Upper Triassic Xujiahe Formation(T_(3)χ),as well as the Middle Jurassic Shaximiao(J_(2)s)and Qianfoya(J_(2)q)formations.Based on this,we explored the sources of the natural gas in the Zhongjiang gas field and determined the natural gas migration patterns and their effects on the properties of light hydrocarbons in the natural gas.The results indicate that the Lower Jurassic lacustrine source rocks of the Zhongjiang gas field contain humic organic matter,with vitrinite reflectance(R_(0))values ranging from 0.86%to 0.98%.Samples meeting the criterion for effective source rocks[total organic carbon(TOC)content≥0.75%]exhibited an average TOC content of merely 1.02%,suggesting significantly lower hydrocarbon generation potential than source rocks in the underlying T3x,which show higher thermal maturity and TOC contents.For natural gas samples from T_(3)χ^(2),T_(3)χ^(4),J_(2)s,and J_(2)q reservoirs,their C_(5-7)iso-alkane content was significantly higher than their n-alkane content,and their methylcyclohexane(MCH)index ranged from 59.0%to 77.3%,indicating the predominance of methylcyclohexane in C_(7)light hydrocarbons.As indicated by the origin identification and gas-source correlation based on the geochemical features of light hydrocarbons,the natural gas in the Zhongjiang gas field is typical coal-derived gas.The gas from the primary pay zone of the Shaximiao Formation,with significantly high K_(1),(P_(2)+N_(2))/C_(7),and P_(3)/C_(7)values,predominantly originated from the 5th member of the T3x and migrated in the free phase,with a small amount possibly sourced from the Lower Jurassic source rocks.The dissolution and adsorption during gas migration led to a decrease in the aromatic content in C_(6-7)light hydrocarbons and an increase in the isoheptane values.Therefore,their effects must be considered when determining the gas origin and thermal maturity based on the aromatic content in C_(6-7) light hydrocarbons and iso-heptane values.
