The microstructure and precipitation mechanism of ultra-thin hotstrip produced by CSP technology were analyzed by electron backscattered diffraction(EBSD), H-800 transmission electronmicroscope(TEM)and thermodynamics ...The microstructure and precipitation mechanism of ultra-thin hotstrip produced by CSP technology were analyzed by electron backscattered diffraction(EBSD), H-800 transmission electronmicroscope(TEM)and thermodynamics theory. The EBSD results show thatthe finishing hot rolling microstructures are mixture ofrecrystallized and deformed austenite. After phase transformation,ferrite gra- ins embody substructures and dislocations that ledultra-thin hot strip high strength and relatively low elongationrate. TEM observations show that there are a lot of fine anddispersive precipitates in microstructure.展开更多
A three-dimensional steady model of temperature fluctuation with melt convection is studied. It is proved that there exists a unique and stable solution in the model and the solution is expressed in a Fourier series f...A three-dimensional steady model of temperature fluctuation with melt convection is studied. It is proved that there exists a unique and stable solution in the model and the solution is expressed in a Fourier series form. It theoretically confirms the mechanism of melt nucleating: as long as the convection with transverse directions exists, the melt temperature on the front of the solid-liquid interface would be not only periodical along the direction which is perpendicular to the direction of crystal growth, but also oscillatory and exponential decay along the direction of crystal growth; this oscillatory property, i.e. temperature fluctuation, leads to local supercooling, accelerates local temperature fluctuation and then results in a large number of nuclei.展开更多
The moving boundary non-equilibrium segregation duringrecrystallization and the influence of pre-deformation in Fe-30/100Ni alloy at 1000 deg. C was investigated by the PTA(particle trackingautoradiography)technique, ...The moving boundary non-equilibrium segregation duringrecrystallization and the influence of pre-deformation in Fe-30/100Ni alloy at 1000 deg. C was investigated by the PTA(particle trackingautoradiography)technique, optical and electron microscopy. The re-Sults indicated that intensity of boron segregation on movingboundary after different deformation is concerned with thepre-deformation Degree and the moving speed of the boundary. TheTEM(transmission electron microscopy(result showed that thedislocation density Nearby the moving boundary increase obviously.The phenomena are discussed by the widening grain boundary mechanism.展开更多
The dynamic process of non-equilibrium grain boundary segregation of traceboron in Fe-40 percent Ni alloy during cooling and the effect of cooling rate were investigated byboron tracking autoradiography technique. The...The dynamic process of non-equilibrium grain boundary segregation of traceboron in Fe-40 percent Ni alloy during cooling and the effect of cooling rate were investigated byboron tracking autoradiography technique. The results indicate that during cooling process, theamount of segregated boron on grain boundary firstly increases fast, then enters a comparativelyeven increasing stage and increases rapidly again at the third stage. The details of each stagevaried with cooling rate are explained. When the segregation develops to a certain degree, thesegregated boron atoms transform from solute status to precipitate status.展开更多
基金[This work is financially supported by the state foundation for key projects: Fundamental Research on New Generation of Steels (No: G1998061500).]
文摘The microstructure and precipitation mechanism of ultra-thin hotstrip produced by CSP technology were analyzed by electron backscattered diffraction(EBSD), H-800 transmission electronmicroscope(TEM)and thermodynamics theory. The EBSD results show thatthe finishing hot rolling microstructures are mixture ofrecrystallized and deformed austenite. After phase transformation,ferrite gra- ins embody substructures and dislocations that ledultra-thin hot strip high strength and relatively low elongationrate. TEM observations show that there are a lot of fine anddispersive precipitates in microstructure.
基金This work was financially supported by the Major State Basic Research Development Program of China (No. G2000067206_1).
文摘A three-dimensional steady model of temperature fluctuation with melt convection is studied. It is proved that there exists a unique and stable solution in the model and the solution is expressed in a Fourier series form. It theoretically confirms the mechanism of melt nucleating: as long as the convection with transverse directions exists, the melt temperature on the front of the solid-liquid interface would be not only periodical along the direction which is perpendicular to the direction of crystal growth, but also oscillatory and exponential decay along the direction of crystal growth; this oscillatory property, i.e. temperature fluctuation, leads to local supercooling, accelerates local temperature fluctuation and then results in a large number of nuclei.
基金financially supported by the National Natural Science foundation of China (No.59291000).
文摘The moving boundary non-equilibrium segregation duringrecrystallization and the influence of pre-deformation in Fe-30/100Ni alloy at 1000 deg. C was investigated by the PTA(particle trackingautoradiography)technique, optical and electron microscopy. The re-Sults indicated that intensity of boron segregation on movingboundary after different deformation is concerned with thepre-deformation Degree and the moving speed of the boundary. TheTEM(transmission electron microscopy(result showed that thedislocation density Nearby the moving boundary increase obviously.The phenomena are discussed by the widening grain boundary mechanism.
基金This work was financially supported by the Projects of Development of the State Key Fundamental Research(National 973 Project)(No.G19980601507).]
文摘The dynamic process of non-equilibrium grain boundary segregation of traceboron in Fe-40 percent Ni alloy during cooling and the effect of cooling rate were investigated byboron tracking autoradiography technique. The results indicate that during cooling process, theamount of segregated boron on grain boundary firstly increases fast, then enters a comparativelyeven increasing stage and increases rapidly again at the third stage. The details of each stagevaried with cooling rate are explained. When the segregation develops to a certain degree, thesegregated boron atoms transform from solute status to precipitate status.
