Effects of Zirconium on the chemical component and size distribution of Ti-bearing inclusions, favored the grain refinement of the welding reduced, coarse-grained heat affected zone （CGHAZ） with enhanced impact toug...Effects of Zirconium on the chemical component and size distribution of Ti-bearing inclusions, favored the grain refinement of the welding reduced, coarse-grained heat affected zone （CGHAZ） with enhanced impact toughness in Ti-killed steels, which were examined based on experimental observations and thermodynamic calculations. It indicated that the chemical constituents of inclusions gradually varied from the TiO oxide to the Ti-O＋Zr-O compound oxide and a single phase of the ZrO2 oxide, as the Zr content increased from zero to 0.0100%. A trace of Zr （0.0030%-0.0080%, depending on the oxygen content in liquid steel） provided a large amount of nucleating core for Ti oxide because of the larger specific density of ZrO2 oxide, and produced a small size distribution of the inclusions favorable for acicular ferrite transformation with a high nucleation rate in the CGHAZ, and a high volume fraction of acicular ferrite was obtained in the CGHAZ, with enhanced impact toughness. Otherwise, a high content of Zr （-0.0100%） produced a single phase Zr02, which was impotent to nucleate acicular ferrite, and a microstructure composed of ferrite side plate and grain boundary ferrite developed in the CGHAZ. The experimental results were confirmed by thermodynamic calculations.展开更多
The Hot deformation and martensitic transformation behaviors of Fe-32%Ni alloy was investigated by measurements of electrical resistance and X-ray diffraction. With the increase in strain, the austenite goes through f...The Hot deformation and martensitic transformation behaviors of Fe-32%Ni alloy was investigated by measurements of electrical resistance and X-ray diffraction. With the increase in strain, the austenite goes through from the work-hardened to the partial dynamcally re-crystallized and then to the completed dynamically re-crystallized. The martensitic transformation characteristics depend on the austenite states. The work-hardening in small strain is helpful to martensitic transformation due to the low dislocation density and little lattice distortion, while the high dislocation density and severe lattice distortion by the increase in strain will hinder the martensitic nucleation. Once dynamic re-crystallization （ DRX ） takes place, the martensitic transformation will be enhanced again, which is related to the heterogeneous dynamic substructures. The growing DRX grain can enhance the martensitic nucleation due to the low dislocation density near its grain boundary.展开更多
A prototype of multi-gap resistive plate chamber (MRPC) modules with 6 gas gaps of 220 μm used for the time-of-flight (TOF) detectors has been developed by STAR TOF group. A tray (TOFr) composed of 28 MRPC modules wa...A prototype of multi-gap resistive plate chamber (MRPC) modules with 6 gas gaps of 220 μm used for the time-of-flight (TOF) detectors has been developed by STAR TOF group. A tray (TOFr) composed of 28 MRPC modules was constructed and operated in STAR for the d+Au collisions and Au+Au collisions during 2003 RHIC and 2004 RHIC run. Results show its time resolution is 85 ps with the average efficiency of 95% and clear identification of K/π up to 1.6 GeV and proton/ K up to 3.0 GeV.展开更多
文摘Effects of Zirconium on the chemical component and size distribution of Ti-bearing inclusions, favored the grain refinement of the welding reduced, coarse-grained heat affected zone （CGHAZ） with enhanced impact toughness in Ti-killed steels, which were examined based on experimental observations and thermodynamic calculations. It indicated that the chemical constituents of inclusions gradually varied from the TiO oxide to the Ti-O＋Zr-O compound oxide and a single phase of the ZrO2 oxide, as the Zr content increased from zero to 0.0100%. A trace of Zr （0.0030%-0.0080%, depending on the oxygen content in liquid steel） provided a large amount of nucleating core for Ti oxide because of the larger specific density of ZrO2 oxide, and produced a small size distribution of the inclusions favorable for acicular ferrite transformation with a high nucleation rate in the CGHAZ, and a high volume fraction of acicular ferrite was obtained in the CGHAZ, with enhanced impact toughness. Otherwise, a high content of Zr （-0.0100%） produced a single phase Zr02, which was impotent to nucleate acicular ferrite, and a microstructure composed of ferrite side plate and grain boundary ferrite developed in the CGHAZ. The experimental results were confirmed by thermodynamic calculations.
基金the National Natural Science Foundation of China （No. 50471017）.
文摘The Hot deformation and martensitic transformation behaviors of Fe-32%Ni alloy was investigated by measurements of electrical resistance and X-ray diffraction. With the increase in strain, the austenite goes through from the work-hardened to the partial dynamcally re-crystallized and then to the completed dynamically re-crystallized. The martensitic transformation characteristics depend on the austenite states. The work-hardening in small strain is helpful to martensitic transformation due to the low dislocation density and little lattice distortion, while the high dislocation density and severe lattice distortion by the increase in strain will hinder the martensitic nucleation. Once dynamic re-crystallization （ DRX ） takes place, the martensitic transformation will be enhanced again, which is related to the heterogeneous dynamic substructures. The growing DRX grain can enhance the martensitic nucleation due to the low dislocation density near its grain boundary.
基金Supported by National Foundation of Natural Sciences of China (10375062)
文摘A prototype of multi-gap resistive plate chamber (MRPC) modules with 6 gas gaps of 220 μm used for the time-of-flight (TOF) detectors has been developed by STAR TOF group. A tray (TOFr) composed of 28 MRPC modules was constructed and operated in STAR for the d+Au collisions and Au+Au collisions during 2003 RHIC and 2004 RHIC run. Results show its time resolution is 85 ps with the average efficiency of 95% and clear identification of K/π up to 1.6 GeV and proton/ K up to 3.0 GeV.
