La57.6Al17.5(Cu,Ni)24.9 and La64Al14(Cu,Ni)22 bulk metallic glasses (BMGs) were prepared by copper-mould casting method. Plastic deformation behavior of the two BMGs at various loading rates was studied by nanoindenta...La57.6Al17.5(Cu,Ni)24.9 and La64Al14(Cu,Ni)22 bulk metallic glasses (BMGs) were prepared by copper-mould casting method. Plastic deformation behavior of the two BMGs at various loading rates was studied by nanoindentation. The results showed that the La57.6Al17.5(Cu,Ni)24.9 BMG with a glass transition temperature of 423 K exhibited prominent serrated flow at low loading rates, whereas less pronounced serrated flow at high rates during nanoindentation. In contrast, the La64Al14(Cu,Ni)22 BMG with a glass transition temperature of 401 K exhibited prominent serrated flow at high loading rates. The different rate dependency of serrated flow in the two La-based BMGs is related to the different glass transition temperature, and consequently the degree of viscous flow during indentation at room temperature. A smoother flow occurs in the alloy with relatively lower glass transition temperature, due to the relaxation of stress concentration.展开更多
Flow behavior was observed in a simplified model cavity of a multiphase High Level Liquid Waste (HLLW) reprocessing glass melter. Electrodes were set to generate Joule-heating flow in the cavity. A chaotic flow occurr...Flow behavior was observed in a simplified model cavity of a multiphase High Level Liquid Waste (HLLW) reprocessing glass melter. Electrodes were set to generate Joule-heating flow in the cavity. A chaotic flow occurred because the lower part of the cavity was heated while the top surface of the cavity was cooled. Downflow and upflow occurred alternately in cavities. The shape of the cavity was a sloping bottom cavity, which was similar in shape to the real glass melter. To know the flow behavior in the cavity, 1-D flow behavior and 2-D flow behavior were measured in an experiment and simulated by an original CFD code. In the sloping bottom cavity, chaotic flow occurred in the upper part of the cavity. In the case of the sloping bottom cavity which had the same set of electrodes as the glass melter, the effect of the downflow near the electrodes decreased. The same phenomena could be predicted in the melter. The experimental results were also used to validate the CFD code, which will be helpful for developing a multiphase Joule-heating flow predicting.展开更多
Upon deforming a metallic glass at low temperatures, shear tends to localize and this leads to a brittle behavior. However, in the high temperature, and particularly in the supercooled liquid region, homogeneous defor...Upon deforming a metallic glass at low temperatures, shear tends to localize and this leads to a brittle behavior. However, in the high temperature, and particularly in the supercooled liquid region, homogeneous deformation begins to take place. A bulk amorphous Zr 10Al 5Ti 17.9Cu 14.6Ni alloy was observed to exhibit the Newtonian behavior at low strain rates but becomes non Newtonian at high strain rates in the supercooled liquid region. Structures of the amorphous material, both before and after deformation, were examined using X ray diffraction and high resolution electron microscopy. Results showed the presence of nanocrystallites in the deformed samples. Thus, the non Newtonian behavior is attributable to the concurrent crystallization of the amorphous structure during deformation. A mechanistic model is presented to interpret the observed non Newtonian result. A phenomenological approach is also used to develop the deformation map for bulk metallic glasses in the supercooled liquid region.展开更多
We measure the current–voltage（I–V） characteristics for the single crystal of Tl0.4K0.41Fe1.71Se2 with the superconducting transition temperature（TC） around 30.5 K, under a 10 T magnetic field applied perpendicu...We measure the current–voltage（I–V） characteristics for the single crystal of Tl0.4K0.41Fe1.71Se2 with the superconducting transition temperature（TC） around 30.5 K, under a 10 T magnetic field applied perpendicular and parallel to the ab plane. We find that the shapes of the I–V isotherms are very different from the description by the vortex-glass（VG） model.Combining theoretical calculations and analysis of the ρH⊥ab–T and ρH ab–T data, we give an explicit discussion over the suitability of the VG model for the A0.8Fe2Se2 superconductors, and point out the possibility of the material acting as a convenient platform for re-examination and further study of the complex vortex behaviors in the layered superconductors.展开更多
基金This work was financially supported by the National Natural Science Foundation of China (No.50571109, 10572142 and 10432050)the Knowledge Innovation Program of the Chinese Academy of Sciences.
文摘La57.6Al17.5(Cu,Ni)24.9 and La64Al14(Cu,Ni)22 bulk metallic glasses (BMGs) were prepared by copper-mould casting method. Plastic deformation behavior of the two BMGs at various loading rates was studied by nanoindentation. The results showed that the La57.6Al17.5(Cu,Ni)24.9 BMG with a glass transition temperature of 423 K exhibited prominent serrated flow at low loading rates, whereas less pronounced serrated flow at high rates during nanoindentation. In contrast, the La64Al14(Cu,Ni)22 BMG with a glass transition temperature of 401 K exhibited prominent serrated flow at high loading rates. The different rate dependency of serrated flow in the two La-based BMGs is related to the different glass transition temperature, and consequently the degree of viscous flow during indentation at room temperature. A smoother flow occurs in the alloy with relatively lower glass transition temperature, due to the relaxation of stress concentration.
文摘Flow behavior was observed in a simplified model cavity of a multiphase High Level Liquid Waste (HLLW) reprocessing glass melter. Electrodes were set to generate Joule-heating flow in the cavity. A chaotic flow occurred because the lower part of the cavity was heated while the top surface of the cavity was cooled. Downflow and upflow occurred alternately in cavities. The shape of the cavity was a sloping bottom cavity, which was similar in shape to the real glass melter. To know the flow behavior in the cavity, 1-D flow behavior and 2-D flow behavior were measured in an experiment and simulated by an original CFD code. In the sloping bottom cavity, chaotic flow occurred in the upper part of the cavity. In the case of the sloping bottom cavity which had the same set of electrodes as the glass melter, the effect of the downflow near the electrodes decreased. The same phenomena could be predicted in the melter. The experimental results were also used to validate the CFD code, which will be helpful for developing a multiphase Joule-heating flow predicting.
文摘Upon deforming a metallic glass at low temperatures, shear tends to localize and this leads to a brittle behavior. However, in the high temperature, and particularly in the supercooled liquid region, homogeneous deformation begins to take place. A bulk amorphous Zr 10Al 5Ti 17.9Cu 14.6Ni alloy was observed to exhibit the Newtonian behavior at low strain rates but becomes non Newtonian at high strain rates in the supercooled liquid region. Structures of the amorphous material, both before and after deformation, were examined using X ray diffraction and high resolution electron microscopy. Results showed the presence of nanocrystallites in the deformed samples. Thus, the non Newtonian behavior is attributable to the concurrent crystallization of the amorphous structure during deformation. A mechanistic model is presented to interpret the observed non Newtonian result. A phenomenological approach is also used to develop the deformation map for bulk metallic glasses in the supercooled liquid region.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11404002,11404003,and 11074001)the Scientific Research Foundation for the Returned Overseas Chinese Scholarsthe"211 Project"of Anhui University,China(Grant No.J01001319-J10113190007)
文摘We measure the current–voltage（I–V） characteristics for the single crystal of Tl0.4K0.41Fe1.71Se2 with the superconducting transition temperature（TC） around 30.5 K, under a 10 T magnetic field applied perpendicular and parallel to the ab plane. We find that the shapes of the I–V isotherms are very different from the description by the vortex-glass（VG） model.Combining theoretical calculations and analysis of the ρH⊥ab–T and ρH ab–T data, we give an explicit discussion over the suitability of the VG model for the A0.8Fe2Se2 superconductors, and point out the possibility of the material acting as a convenient platform for re-examination and further study of the complex vortex behaviors in the layered superconductors.
