The purpose of this paper is to study large-sized copper billets refined with 5N ultrahigh purity after vacuum melting and directional solidifi-cation （VMDS）. The precise impurity analysis of copper billets was carr...The purpose of this paper is to study large-sized copper billets refined with 5N ultrahigh purity after vacuum melting and directional solidifi-cation （VMDS）. The precise impurity analysis of copper billets was carried out with a glow discharge mass spectrometer （GDMS）. The re-sults demonstrate that the total concentration of twenty-two impurities is decreased by 63.1wt.%-66.5 wt.%. Ag, P, S, Na, Mg, Se, Zn, In and Bi are easy to be removed due to lgPimp - lgPCu 1.5, and they can be removed effectively under the vacuum condition of 1650-1700 K for 30 min. The electrical conductivity of 5N copper is higher than that of the raw material as the impurity concentrations decrease. The segrega-tion effect in directional solidification can be remarkable when the equilibrium distribution coefficient （k0） value is less than 0.65 due to the strong affinity of Cu for some metallic and non-metallic impurities.展开更多
CuNi10Fe1Mn alloy billet under rotating electromagnetic field (REF) was characterized in this work. The change of the crystal orientation was first explored by X-ray diffraction (XRD) and scanning election microscope ...CuNi10Fe1Mn alloy billet under rotating electromagnetic field (REF) was characterized in this work. The change of the crystal orientation was first explored by X-ray diffraction (XRD) and scanning election microscope (SEM); the corrosion resistance was done by three electrodes system, and the natural sea water was used as corrosion medium. The results demonstrate that the strongest crystal orientation is transformed from crystal plane (200) to (111); moreover, the crystal plane (111) whose intensity is the strongest on the cross section and vertical section with REF causes the tubes be rolled easily, and the corrosion resistance of the billet is increasing with REF. As a result, properties of CuNi10Fe1Mn alloy tubes can be improved by REF.展开更多
故障树分析(Fault Tree Analysis,FTA)是一种采用倒立树状的逻辑因果关系图(包括顶事件、事件、门等)进行故障和风险分析的方法,结合轨道交通系统的设计特点以及标准要求,系统研究了在牵引控制回路中展开FTA的方法及流程。FTA与风险树...故障树分析(Fault Tree Analysis,FTA)是一种采用倒立树状的逻辑因果关系图(包括顶事件、事件、门等)进行故障和风险分析的方法,结合轨道交通系统的设计特点以及标准要求,系统研究了在牵引控制回路中展开FTA的方法及流程。FTA与风险树、安全完整性等级(SIL)分析、故障模式及影响分析(FMECA)等RAMS工作紧密相关,可以为列车子系统设计尤其是安全相关子系统的可靠性指标评估、单点故障消除以及共因失效分析等提供系统的解决方法。展开更多
Microstructure formation and transition of undercooled bulk Ni70.2Si29.8 eutectic alloy melt were investigated by melt fluxing,cyclical overheating and cooling under high-frequency vacuum melting.The maximum undercool...Microstructure formation and transition of undercooled bulk Ni70.2Si29.8 eutectic alloy melt were investigated by melt fluxing,cyclical overheating and cooling under high-frequency vacuum melting.The maximum undercooling of the alloy melt amounted to 428 K.Scanning electron microscope(SEM),energy-dispersive X-ray spectroscopy(EDS)and optical microscopy techniques(OM)were adopted to investigate the microstructure and identify the phase composition.The cooling curves of eutectic alloys upon solidification which were subjected to different undercoolings were described and compared.The complex microstructure evolution was observed in the as-solidified samples with the increase of undercooling.Surprisingly,an extremely fine microstructure was achieved at the max undercooling of 428 K,and the lamellar distance of about 50-100 nm was observed.Based on the solution entropy of eutectic phases,the microstructure transition with the undercooling was analyzed.Calculated results showed that the microstructure transition process was ascribed to solution entropy of transition,i.e.,the complex microstructure evolution was attributed to a transition from faceted-faceted(FF)→faceted-nonfaceted(FN)→nonfaceted-nonfaceted(NN)eutectic systems concurring with increased undercooling.展开更多
文摘The purpose of this paper is to study large-sized copper billets refined with 5N ultrahigh purity after vacuum melting and directional solidifi-cation （VMDS）. The precise impurity analysis of copper billets was carried out with a glow discharge mass spectrometer （GDMS）. The re-sults demonstrate that the total concentration of twenty-two impurities is decreased by 63.1wt.%-66.5 wt.%. Ag, P, S, Na, Mg, Se, Zn, In and Bi are easy to be removed due to lgPimp - lgPCu 1.5, and they can be removed effectively under the vacuum condition of 1650-1700 K for 30 min. The electrical conductivity of 5N copper is higher than that of the raw material as the impurity concentrations decrease. The segrega-tion effect in directional solidification can be remarkable when the equilibrium distribution coefficient （k0） value is less than 0.65 due to the strong affinity of Cu for some metallic and non-metallic impurities.
基金financially supported by the Fundamental Research Fund for the Zhejiang Provincial Laboratory of Testing and Deep Processing for Measuring and Cutting Tools(No.ZD201202)
文摘CuNi10Fe1Mn alloy billet under rotating electromagnetic field (REF) was characterized in this work. The change of the crystal orientation was first explored by X-ray diffraction (XRD) and scanning election microscope (SEM); the corrosion resistance was done by three electrodes system, and the natural sea water was used as corrosion medium. The results demonstrate that the strongest crystal orientation is transformed from crystal plane (200) to (111); moreover, the crystal plane (111) whose intensity is the strongest on the cross section and vertical section with REF causes the tubes be rolled easily, and the corrosion resistance of the billet is increasing with REF. As a result, properties of CuNi10Fe1Mn alloy tubes can be improved by REF.
文摘故障树分析(Fault Tree Analysis,FTA)是一种采用倒立树状的逻辑因果关系图(包括顶事件、事件、门等)进行故障和风险分析的方法,结合轨道交通系统的设计特点以及标准要求,系统研究了在牵引控制回路中展开FTA的方法及流程。FTA与风险树、安全完整性等级(SIL)分析、故障模式及影响分析(FMECA)等RAMS工作紧密相关,可以为列车子系统设计尤其是安全相关子系统的可靠性指标评估、单点故障消除以及共因失效分析等提供系统的解决方法。
基金supported by the China Postdoctoral Science Foundation(Grant No 20090450102)
文摘Microstructure formation and transition of undercooled bulk Ni70.2Si29.8 eutectic alloy melt were investigated by melt fluxing,cyclical overheating and cooling under high-frequency vacuum melting.The maximum undercooling of the alloy melt amounted to 428 K.Scanning electron microscope(SEM),energy-dispersive X-ray spectroscopy(EDS)and optical microscopy techniques(OM)were adopted to investigate the microstructure and identify the phase composition.The cooling curves of eutectic alloys upon solidification which were subjected to different undercoolings were described and compared.The complex microstructure evolution was observed in the as-solidified samples with the increase of undercooling.Surprisingly,an extremely fine microstructure was achieved at the max undercooling of 428 K,and the lamellar distance of about 50-100 nm was observed.Based on the solution entropy of eutectic phases,the microstructure transition with the undercooling was analyzed.Calculated results showed that the microstructure transition process was ascribed to solution entropy of transition,i.e.,the complex microstructure evolution was attributed to a transition from faceted-faceted(FF)→faceted-nonfaceted(FN)→nonfaceted-nonfaceted(NN)eutectic systems concurring with increased undercooling.
