The alteration of dislocation arrays in the process of strain hardening for normalized carbon steel 1035 was investigated by transmission electron microscopy. At primary stage the separated dislocation lines tend to ...The alteration of dislocation arrays in the process of strain hardening for normalized carbon steel 1035 was investigated by transmission electron microscopy. At primary stage the separated dislocation lines tend to form tangles and networks, dislocation cells appear at the secondary stage, the amount of the cells increases significantly, its average dimension does not change and the cell walls become clear. The third stage of strain hardening was observed in the process from necking to fracture and shows a straight line segment on the lg σ -lg ε curve, at this time the dislocation cells become smaller and tend to form band structure.展开更多
The relationships between fatigue threshold △Kth and the initial yield .strength σ0 of normalized 1035 steel after various prestrain (at fist, second and third hardening stages respectively) were investigated throug...The relationships between fatigue threshold △Kth and the initial yield .strength σ0 of normalized 1035 steel after various prestrain (at fist, second and third hardening stages respectively) were investigated through the analysis of theσ-εcurves and transmission electron microscope (TEM). After prestraining at first or second hardening stage, there is a marked drop in the values of △Kth and σ0. This is in correspondence with the depinning of the solute atoms from the dislocation lines in the Cottrell atmosphere.At the third hardening stage of prestrain the fatigue threshold increases rapidly and △Kth is even 1.6 times as large as the original value. This is because at this stage no dislocation-cell free areas can be found and the refinement of the dislocation cells occurs with the increase in the prestrain level.展开更多
High dielectric constant can be reached in a reductive-sintered Sr_(1-x)Ba_(x)TiO_(3)barrier-layer capacitor with core‒rim structures as dominant microstructural features.By SEM and aberration-corrected TEM observatio...High dielectric constant can be reached in a reductive-sintered Sr_(1-x)Ba_(x)TiO_(3)barrier-layer capacitor with core‒rim structures as dominant microstructural features.By SEM and aberration-corrected TEM observations,an interfacial zone between the core and rim,named as white-rim(w-rim),was found always enriched with Ba,while the core was free of Ba solution.The reductive liquid-phase sintering resulted in three times the concentrations of oxygen vacancies(VO)into cores and rims compared to their A-site vacancies(VA),while enabling the highest concentration of VO(~17%)without VA in w-rim.The strained core/w-rim interfaces,with obvious interfacial polarizations,which can effectively raise the dielectric constant,were expected to be created from a temporary equilibrium between the cores and the liquidphase.The synergetic evolution of core‒rim structures,SreO vacancies,multiple internal polarized structures can be utilized to better control and optimize dielectric behaviors and other functionalities for perovskite capacitors and other multi-functional ceramics.展开更多
文摘The alteration of dislocation arrays in the process of strain hardening for normalized carbon steel 1035 was investigated by transmission electron microscopy. At primary stage the separated dislocation lines tend to form tangles and networks, dislocation cells appear at the secondary stage, the amount of the cells increases significantly, its average dimension does not change and the cell walls become clear. The third stage of strain hardening was observed in the process from necking to fracture and shows a straight line segment on the lg σ -lg ε curve, at this time the dislocation cells become smaller and tend to form band structure.
文摘The relationships between fatigue threshold △Kth and the initial yield .strength σ0 of normalized 1035 steel after various prestrain (at fist, second and third hardening stages respectively) were investigated through the analysis of theσ-εcurves and transmission electron microscope (TEM). After prestraining at first or second hardening stage, there is a marked drop in the values of △Kth and σ0. This is in correspondence with the depinning of the solute atoms from the dislocation lines in the Cottrell atmosphere.At the third hardening stage of prestrain the fatigue threshold increases rapidly and △Kth is even 1.6 times as large as the original value. This is because at this stage no dislocation-cell free areas can be found and the refinement of the dislocation cells occurs with the increase in the prestrain level.
基金supported by the Postdoctoral Fellowship Program of CPSF(Grant No.GZC20240969)the National Natural Science Foundation of China(Grants No.51532006 and No.51702168)+3 种基金Shanghai Technical Service Center for Advanced Ceramics Structure Design and Precision Manufacturing(NO.20DZ2294000)the support from Beijing Municipal Natural Science Foundation(Grant No.1212016)the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB36000000)the CAS Pioneer Hundred Talents Program.
文摘High dielectric constant can be reached in a reductive-sintered Sr_(1-x)Ba_(x)TiO_(3)barrier-layer capacitor with core‒rim structures as dominant microstructural features.By SEM and aberration-corrected TEM observations,an interfacial zone between the core and rim,named as white-rim(w-rim),was found always enriched with Ba,while the core was free of Ba solution.The reductive liquid-phase sintering resulted in three times the concentrations of oxygen vacancies(VO)into cores and rims compared to their A-site vacancies(VA),while enabling the highest concentration of VO(~17%)without VA in w-rim.The strained core/w-rim interfaces,with obvious interfacial polarizations,which can effectively raise the dielectric constant,were expected to be created from a temporary equilibrium between the cores and the liquidphase.The synergetic evolution of core‒rim structures,SreO vacancies,multiple internal polarized structures can be utilized to better control and optimize dielectric behaviors and other functionalities for perovskite capacitors and other multi-functional ceramics.
