In contrast to their conventional crystalline counterparts,amorphous solids exhibit diverse dynamic relaxation mechanisms under external stimuli.The challenge to understanding their behavior lies in unifying microscop...In contrast to their conventional crystalline counterparts,amorphous solids exhibit diverse dynamic relaxation mechanisms under external stimuli.The challenge to understanding their behavior lies in unifying microscopic dynamics,relaxation,and macroscopic deformation.This study establishes a potential link by quantifying the characteristic time of the anelastic-to-plastic transition through dynamic mechanical relaxation and stress relaxation tests across a wide temperature range in both the supercooled liquid and the glassy state.It is found that the stress relaxation time in the glassy solids follows an Arrhenius relationship,aligning with the mainαrelaxation time,and unveils a finding:αrelaxation continues to govern deformation even below the glass transition,challenging previous assumptions of the role of secondaryβrelaxation.A hierarchically constrained atomic dynamics model rationalizes the temperature dependence ofαrelaxation and the transition fromβtoαrelaxation,also providing evidence that the stretched exponent in the Kohlrausch-Williams-Watts equation can serve as an order parameter.This work highlights the role ofαrelaxation in the glassy state and contributes to elucidating the potential correlation between relaxation and deformation in amorphous materials.展开更多
The stretched exponent Kohlrausch-Williams-Watts(KWW)equation,which is to some extent equivalent to the generalized Maxwell viscoelastic model,is widely employed for analyzing relaxation dynamics and nonelastic deform...The stretched exponent Kohlrausch-Williams-Watts(KWW)equation,which is to some extent equivalent to the generalized Maxwell viscoelastic model,is widely employed for analyzing relaxation dynamics and nonelastic deformation of amorphous solids.However,it cannot reveal the underlying physical mechanisms of anelasticity.In this study,based on the potential atomic mechanisms of amorphous solids within a strain field and the traditional viscoelastic model,we introduced a physical-mechanical model involving hierarchically constrained atomic motion around defect sites.This model deduces that fast atoms move first,subsequently facilitating more complex atomic rearrangements under thermomechanical loading.These atom movement mechanisms are involved in the evolution of deformation units,such as shear transformation zones(STZs).Initially,anelasticity is associated with isolated STZs because of back stress arising from the matrix.Subsequently,the percolation of STZ by the motion of atoms owing to STZ interactions leads to irreversible deformation.The model was validated by describing the elastic,anelastic,and plastic components of stress relaxation in a La60Ni15Al25metallic glass.Furthermore,as STZs are connected toαandβrelaxation processes,the model can be used for parameter description and component analysis of dynamic stress relaxation.The current study supplements the traditional flow defect model,providing insights into the deformation mechanisms of metallic glasses from the perspective of viscoelastic mechanics and their correlation with dynamic relaxation processes.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.52271153,and 12472069)the Natural Science Basic Research Plan for Distinguished Young Scholars in Shaanxi Province(Grant No.2021JC-12)+6 种基金financially supported by the National Natural Science Foundation of China(Grant No.12472112)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant Nos.XDB0620103,and XDB0510301)financial support from Research Grant Council(RGC)the Hong Kong Government through the General Research Fund(GRF)(Grant Nos.City U11200719,and City U11213118)financial support from Proyecto PID2020-112975GB-I00 de investigación financiado por MCIN/AEI/10.13039/501100011033Generalitat de Catalunya,AGAUR(Grant No.2021-SGR-00343)supported by the Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University(Grant No.CX2023054)。
文摘In contrast to their conventional crystalline counterparts,amorphous solids exhibit diverse dynamic relaxation mechanisms under external stimuli.The challenge to understanding their behavior lies in unifying microscopic dynamics,relaxation,and macroscopic deformation.This study establishes a potential link by quantifying the characteristic time of the anelastic-to-plastic transition through dynamic mechanical relaxation and stress relaxation tests across a wide temperature range in both the supercooled liquid and the glassy state.It is found that the stress relaxation time in the glassy solids follows an Arrhenius relationship,aligning with the mainαrelaxation time,and unveils a finding:αrelaxation continues to govern deformation even below the glass transition,challenging previous assumptions of the role of secondaryβrelaxation.A hierarchically constrained atomic dynamics model rationalizes the temperature dependence ofαrelaxation and the transition fromβtoαrelaxation,also providing evidence that the stretched exponent in the Kohlrausch-Williams-Watts equation can serve as an order parameter.This work highlights the role ofαrelaxation in the glassy state and contributes to elucidating the potential correlation between relaxation and deformation in amorphous materials.
基金supported by the National Natural Science Foundation of China(Grant Nos.12472069,52271153,12072344)the Natural Science Basic Research Plan for Distinguished Young Scholars in Shaanxi Province(Grant No.2021JC-12)+3 种基金the Natural Science Foundation of Shaanxi Province(Grant No.2025GH-YBXM046)the Youth Innovation Promotion Association of the Chinese Academy of Sciences,Research Grant Council(RGC),the Hong Kong government(SAR)through the General Research Fund(GRF)(Grant Nos.City U11200719,City U11213118)PID2023-146623NB-I00 and Maria de Maeztu Units of Excellence Programme CEX2023-001300-M funded by MICIU/AEI/10.13039/5011000110332021-SGR-00343 funded by Generalitat de Catalunya/AGAUR。
文摘The stretched exponent Kohlrausch-Williams-Watts(KWW)equation,which is to some extent equivalent to the generalized Maxwell viscoelastic model,is widely employed for analyzing relaxation dynamics and nonelastic deformation of amorphous solids.However,it cannot reveal the underlying physical mechanisms of anelasticity.In this study,based on the potential atomic mechanisms of amorphous solids within a strain field and the traditional viscoelastic model,we introduced a physical-mechanical model involving hierarchically constrained atomic motion around defect sites.This model deduces that fast atoms move first,subsequently facilitating more complex atomic rearrangements under thermomechanical loading.These atom movement mechanisms are involved in the evolution of deformation units,such as shear transformation zones(STZs).Initially,anelasticity is associated with isolated STZs because of back stress arising from the matrix.Subsequently,the percolation of STZ by the motion of atoms owing to STZ interactions leads to irreversible deformation.The model was validated by describing the elastic,anelastic,and plastic components of stress relaxation in a La60Ni15Al25metallic glass.Furthermore,as STZs are connected toαandβrelaxation processes,the model can be used for parameter description and component analysis of dynamic stress relaxation.The current study supplements the traditional flow defect model,providing insights into the deformation mechanisms of metallic glasses from the perspective of viscoelastic mechanics and their correlation with dynamic relaxation processes.
