Electron magnetic circular dichroism opens a new door to explore magnetic properties by transmitted electrons in the transmission electron microscope. However, obtaining quantitative magnetic parameters, such as spin ...Electron magnetic circular dichroism opens a new door to explore magnetic properties by transmitted electrons in the transmission electron microscope. However, obtaining quantitative magnetic parameters, such as spin and orbital magnetic moment with element-specificity, goes a long way along with the development and improvement of this technique both in theoretical and experimental aspects. In this review, we will give a detailed description of the quantitative electron magnetic circular dichroism(EMCD) technique to measure magnetic parameters with spin-specificity, element-specificity,site-specificity, and orbital-spin-specificity. The discussion completely contains the procedures from raw experimental data acquisition to final magnetic parameters, together with the related custom code we have developed.展开更多
The dislocation pipe diffusion of Mn during annealing of 5Mn steel was experimentally investigated using transmission electron microscopy (TEM). Many dislocations existed inside the ferrite and terminated at the α/...The dislocation pipe diffusion of Mn during annealing of 5Mn steel was experimentally investigated using transmission electron microscopy (TEM). Many dislocations existed inside the ferrite and terminated at the α/γin- terface of the sample after intercritieal annealing at 650 ℃ for 1 min. Line scans of Mn distribution demonstrated a high Mn concentration in austenite and Mn enrichment at dislocations, indicating that the dislocation pipe diffusion of Mn during intercritical annealing occurred in addition to the γ/α interface diffusion. In-situ TEM observations at 500 ℃revealed that due to Ostwald ripening, large cementite precipitates grew while small cementite precipitates dissolved via Mn diffusion along the dislocations between them.展开更多
The ability to widely tune the optical properties of amorphous alloys is highly desirable especially for their potential applications in optoelectronic devices.In this work,we demonstrate that introducing oxygen into ...The ability to widely tune the optical properties of amorphous alloys is highly desirable especially for their potential applications in optoelectronic devices.In this work,we demonstrate that introducing oxygen into an amorphous alloy system of Co-Fe-Ta-B enables the formation of various amorphous derivatives ranging from metals to semiconductors,and eventually to insulators.These oxygencontaining amorphous derivatives gradually become transparent with the opened bandgaps,leading to a continuous increase in their optical transmittance.Furthermore,the reflective metal-type amorphous alloy and transparent insulator-type amorphous oxide of the system can be integrated together to realize the full-color tuning over the entire visible spectral range.This provides a new way to develop large-area color coatings with high design flexibility and full-color tunability.We envisage that the design concept proposed in this work is also applicable to many other amorphous alloy systems,from which all types of amorphous materials including alloys,semiconductors and insulators may be developed to show unprecedented optical functionalities.展开更多
The microstructural evolutions of 5Mn steel during various heat treatments have been investiga- ted by in-situ transmission electron microscopy (TEM). The specimen of 5Mn steel was pre- pared using focused ion beam ...The microstructural evolutions of 5Mn steel during various heat treatments have been investiga- ted by in-situ transmission electron microscopy (TEM). The specimen of 5Mn steel was pre- pared using focused ion beam (FIB) milling, which allowed the selection of specific morphology of interest prior to the in-situ observation, The complete austenization at 800 ℃ was verified at the atomic scale by minimizing thermal expansion and sample drift in a heating holder based on micro-electro-mechanical-systems. During annealing at 650 ℃, the formation of reverted austen- ite was dynamically observed, while the morphologies of austenite laths of 5Mn steel after in-situ heating were quite similar to that after ex-situ intereritical annealing. During annealing at 500 ℃, the morphological evolution of cementite and associated Mn diffusion were investigated. It was demonstrated that a combination of FIB sampling and high temperature in-situ TEM enables us to probe the morphological evolution and elemental diffusion of specific areas of interest in steel at high spatial resolution.展开更多
The cementite formation and coarsening behaviors of 0. 2 mass% C-5 mass% Mn steel during tempering at 500℃ were investigated by in-situ transmission electron microscope( TEM). In-situ TEM observation showed uniform...The cementite formation and coarsening behaviors of 0. 2 mass% C-5 mass% Mn steel during tempering at 500℃ were investigated by in-situ transmission electron microscope( TEM). In-situ TEM observation showed uniform distribution of cementite particles at the early stage of tempering in the rapidly heated( 500 ℃ / s) sample. Elemental analysis confirmed that the cementite growth was dominated by Mn diffusion. During the cementite growth,the coarsening behavior of intragranular cementite was significantly controlled by the matrix diffusion,while that of the intergranular cementite was mainly governed by the boundary diffusion. The in-situ TEM observation revealed that the dislocation pipe diffusion of Mn took place during tempering,which accelerated the Mn diffusion between cementite particles. The coarsening rates of individual cementite particles were calculated based on the in-situ TEM observation.展开更多
Mn distribution and austenite morphology at the early stage of intercritical annealing of 5Mn steel were investigated. It was experimentally demonstrated that a newly formed 20 nm-thick austenite was formed without th...Mn distribution and austenite morphology at the early stage of intercritical annealing of 5Mn steel were investigated. It was experimentally demonstrated that a newly formed 20 nm-thick austenite was formed without the partitioning of Mn. The elemental analysis confirmed that the growth of austenite should be controlled by the diffusion of C prior to the diffusion of Mn at a low heating rate. The austenite growth started under negligible-partitioning local equilibrium mode and then switched to partitioning local equilibrium mode. Mn segregation at the γ/α interface suggested that the collector plate mechanism was the essential way of Mn partitioning at the early stage of austenite growth.展开更多
文摘Electron magnetic circular dichroism opens a new door to explore magnetic properties by transmitted electrons in the transmission electron microscope. However, obtaining quantitative magnetic parameters, such as spin and orbital magnetic moment with element-specificity, goes a long way along with the development and improvement of this technique both in theoretical and experimental aspects. In this review, we will give a detailed description of the quantitative electron magnetic circular dichroism(EMCD) technique to measure magnetic parameters with spin-specificity, element-specificity,site-specificity, and orbital-spin-specificity. The discussion completely contains the procedures from raw experimental data acquisition to final magnetic parameters, together with the related custom code we have developed.
基金Item Sponsored by National Key Research and Development Program of China(2016YFB0700402)National Basic Research Program of China(2010CB630800,2015CB921700)+1 种基金National Natural Science Foundation of China(51671112,51471096,51390471,11374174)Tsinghua University Initiative Scientific Research Program(20141081200,20131089311)
文摘The dislocation pipe diffusion of Mn during annealing of 5Mn steel was experimentally investigated using transmission electron microscopy (TEM). Many dislocations existed inside the ferrite and terminated at the α/γin- terface of the sample after intercritieal annealing at 650 ℃ for 1 min. Line scans of Mn distribution demonstrated a high Mn concentration in austenite and Mn enrichment at dislocations, indicating that the dislocation pipe diffusion of Mn during intercritical annealing occurred in addition to the γ/α interface diffusion. In-situ TEM observations at 500 ℃revealed that due to Ostwald ripening, large cementite precipitates grew while small cementite precipitates dissolved via Mn diffusion along the dislocations between them.
基金financially supported by the National Science Fund for Excellent Young Scholars (51922053)the School of Materials Science and Engineering at Tsinghua Universitythe funding from the National Key Research and Development Program (2016YFB0700402)+2 种基金the National Natural Science Foundation of China (51822105 and 11834009)the City University of Hong Kong (9610484)the Shenzhen Research Institute, the City University of Hong Kong
文摘The ability to widely tune the optical properties of amorphous alloys is highly desirable especially for their potential applications in optoelectronic devices.In this work,we demonstrate that introducing oxygen into an amorphous alloy system of Co-Fe-Ta-B enables the formation of various amorphous derivatives ranging from metals to semiconductors,and eventually to insulators.These oxygencontaining amorphous derivatives gradually become transparent with the opened bandgaps,leading to a continuous increase in their optical transmittance.Furthermore,the reflective metal-type amorphous alloy and transparent insulator-type amorphous oxide of the system can be integrated together to realize the full-color tuning over the entire visible spectral range.This provides a new way to develop large-area color coatings with high design flexibility and full-color tunability.We envisage that the design concept proposed in this work is also applicable to many other amorphous alloy systems,from which all types of amorphous materials including alloys,semiconductors and insulators may be developed to show unprecedented optical functionalities.
基金funded by National Basic Research Program of China(2010CB630800,2015CB921700)National Natural Science Foundation of China(51671112,51471096,51390471,11374174)+2 种基金National Key Research and Development Program(2016YFB0700402)National Key Scientific Instruments and Equipment Development Project(2013YQ120353)Tsinghua University(20141081200)
文摘The microstructural evolutions of 5Mn steel during various heat treatments have been investiga- ted by in-situ transmission electron microscopy (TEM). The specimen of 5Mn steel was pre- pared using focused ion beam (FIB) milling, which allowed the selection of specific morphology of interest prior to the in-situ observation, The complete austenization at 800 ℃ was verified at the atomic scale by minimizing thermal expansion and sample drift in a heating holder based on micro-electro-mechanical-systems. During annealing at 650 ℃, the formation of reverted austen- ite was dynamically observed, while the morphologies of austenite laths of 5Mn steel after in-situ heating were quite similar to that after ex-situ intereritical annealing. During annealing at 500 ℃, the morphological evolution of cementite and associated Mn diffusion were investigated. It was demonstrated that a combination of FIB sampling and high temperature in-situ TEM enables us to probe the morphological evolution and elemental diffusion of specific areas of interest in steel at high spatial resolution.
基金Item Sponsored by National Basic Research Program of China(2010CB630800,2015CB921700)National Natural Science Foundation of China(51471096,51001064)Specialized Research Fund for the Dectoral Program of Higher Education of China(20100002120047)
文摘The cementite formation and coarsening behaviors of 0. 2 mass% C-5 mass% Mn steel during tempering at 500℃ were investigated by in-situ transmission electron microscope( TEM). In-situ TEM observation showed uniform distribution of cementite particles at the early stage of tempering in the rapidly heated( 500 ℃ / s) sample. Elemental analysis confirmed that the cementite growth was dominated by Mn diffusion. During the cementite growth,the coarsening behavior of intragranular cementite was significantly controlled by the matrix diffusion,while that of the intergranular cementite was mainly governed by the boundary diffusion. The in-situ TEM observation revealed that the dislocation pipe diffusion of Mn took place during tempering,which accelerated the Mn diffusion between cementite particles. The coarsening rates of individual cementite particles were calculated based on the in-situ TEM observation.
基金Item Sponsored by National Basic Research Program of China(2010CB630800,2015CB921700)National Natural Science Foundation of China(51001064,51471096)+1 种基金Specialized Research Fund for the Doctoral Program of Higher Education of China(20100002120047)Tsinghua University Initiative Scientific Research Program(20141081200)
文摘Mn distribution and austenite morphology at the early stage of intercritical annealing of 5Mn steel were investigated. It was experimentally demonstrated that a newly formed 20 nm-thick austenite was formed without the partitioning of Mn. The elemental analysis confirmed that the growth of austenite should be controlled by the diffusion of C prior to the diffusion of Mn at a low heating rate. The austenite growth started under negligible-partitioning local equilibrium mode and then switched to partitioning local equilibrium mode. Mn segregation at the γ/α interface suggested that the collector plate mechanism was the essential way of Mn partitioning at the early stage of austenite growth.