A study was conducted on the formation of a Cu-rich phase at the scale/steel interface of Cu-containing steel by high-temperature oxidation with varying amounts of A1 and Ni. Both A1 and Ni were found to help decrease...A study was conducted on the formation of a Cu-rich phase at the scale/steel interface of Cu-containing steel by high-temperature oxidation with varying amounts of A1 and Ni. Both A1 and Ni were found to help decrease the amount of the Cu-rich phase at the interface. Analysis of the effects by these elements was conducted in terms of the melting point of the Cu-rich phase, the solid solubility of Cu in austenite, the rate of oxidation, and the amount of Cu-rich phase occlusions in scales. Because of selective oxidation,in which A1 and Ni are oxidized more and less preferentially than Fe, respectively, A1 was weakly concentrated at the interface whereas Ni was more heavily concentrated in it. Thus, A1 exerted no effect on the melting point of the Cu-rich phase, whereas Ni raised its melting point. A1, which was applied at contents of less than 2.0%, decreased the solubility of Cu in austenite but this effect weakened at the interface during oxidation. By contrast,Ni increased the solubility of Cu, and this effect was strengthened with oxidation. Both A1 and Ni promoted internal oxidation and the formation of occlusions.展开更多
High-dispersed nanoscale Cu precipitates often contribute to extremely high strength due to precipitation hardening,and whereas usually lead to degraded toughness for especially ferritic steels.Hence,it is important t...High-dispersed nanoscale Cu precipitates often contribute to extremely high strength due to precipitation hardening,and whereas usually lead to degraded toughness for especially ferritic steels.Hence,it is important to understand the formation behaviors of the Cu precipitates.High-resolution transmission electron microscopy(TEM)is utilized to investigate the structure of Cu precipitates thermally formed in a high-strength low-alloy(HSLA)steel.The Cu precipitates were generally formed from solid solution and at the crystallographic defects such as martensite lath boundaries and dislocations.The Cu precipitates in the same aging condition have various structure of BCC,9 R and FCC,and the structural evolution does not greatly correlate with the actual sizes.The presence of different structures in an individual Cu precipitate is observed,which reflects the structural transformation occurring locally to relax the strain energy.The multiply additions in the steel possibly make the Cu precipitation more complex compared to the binary or the ternary Fe-Cu alloys with Ni or Mn additions.This research gives constructive suggestions on alloying design of Cu-bearing alloy steels.展开更多
Antibacterial activity of AISI420 stainless steel (SS) implanted by copper was investigated. Ions extracted from a metal vapor vacuum arc (MEVVA) are sourced with 100keV energy and a dose range from 0.2×1017 to 2...Antibacterial activity of AISI420 stainless steel (SS) implanted by copper was investigated. Ions extracted from a metal vapor vacuum arc (MEVVA) are sourced with 100keV energy and a dose range from 0.2×1017 to 2.0×1017ions·cm-2. The saturation dose of Cu implantation in AISI420 SS and Cu surface concentration were calculated at the energy of 100keV. The effect of dose on the antibacterial activity was analyzed. Results of antibacterial test show that the saturation dose is the optimum implantation dose for best antibacterial activity, which is above 99% against both Escherichia coli and Staphylococcus aureus. Novel phases such as Fe4Cu3 and Cu9.9Fe0.1 were found in the implanted layer by glancing angle X-ray diffraction (GXRD). The antibacterial activity of AISI420 SS attributes to Cu-contained phase.展开更多
In this article,the influence of simulated thermal cycles for the heat-aff ected zone(HAZ)on the microstructural evolution and mechanical properties in a low-carbon high-strength Cu-bearing steel was investigated by m...In this article,the influence of simulated thermal cycles for the heat-aff ected zone(HAZ)on the microstructural evolution and mechanical properties in a low-carbon high-strength Cu-bearing steel was investigated by microstructural characterization and mechanical tests.The results showed that the microstructure of the coarse-grained heat-aff ected zone(CGHAZ)and the fine-grained heat-aff ected zone(FGHAZ)was mainly comprised of lath martensite,and a mixed microstructure consisting of intercritical ferrite,tempered martensite and retained austenite occurred in the intercritically heat-aff ected zone(ICHAZ)and the subcritically heat-aff ected zone(SCHAZ).Also,8–11%retained austenite and more or less Cu precipitates were observed in the simulated HAZs except for CGHAZ.Charpy impact test indicated that the optimum toughness was obtained in FGHAZ,which was not only associated with grain refinement,but also correlated with deformation-induced transformation of the retained austenite,variant confi guration as interleaved type and a relatively weak variant selection.The toughness of ICHAZ and SCHAZ exhibited a slight downtrend due to the presence of Cu precipitates.The CGHAZ has the lowest toughness in the simulated HAZs,which was attributed to grain coarsening and heavy variant selection.In addition,the contribution of Cu precipitates to yield strength in simulated HAZs was estimated based on Russell–Brown model.It demonstrated an inverse variation trend to toughness.展开更多
文摘A study was conducted on the formation of a Cu-rich phase at the scale/steel interface of Cu-containing steel by high-temperature oxidation with varying amounts of A1 and Ni. Both A1 and Ni were found to help decrease the amount of the Cu-rich phase at the interface. Analysis of the effects by these elements was conducted in terms of the melting point of the Cu-rich phase, the solid solubility of Cu in austenite, the rate of oxidation, and the amount of Cu-rich phase occlusions in scales. Because of selective oxidation,in which A1 and Ni are oxidized more and less preferentially than Fe, respectively, A1 was weakly concentrated at the interface whereas Ni was more heavily concentrated in it. Thus, A1 exerted no effect on the melting point of the Cu-rich phase, whereas Ni raised its melting point. A1, which was applied at contents of less than 2.0%, decreased the solubility of Cu in austenite but this effect weakened at the interface during oxidation. By contrast,Ni increased the solubility of Cu, and this effect was strengthened with oxidation. Both A1 and Ni promoted internal oxidation and the formation of occlusions.
基金Supported by Startup Fund for Youngman Research at SJTU(SFYR at SJTU)National Basic Research Program of China(Grant No.2011CB012904)China Postdoctoral Science Foundation(Grant No.2013M541517)
文摘High-dispersed nanoscale Cu precipitates often contribute to extremely high strength due to precipitation hardening,and whereas usually lead to degraded toughness for especially ferritic steels.Hence,it is important to understand the formation behaviors of the Cu precipitates.High-resolution transmission electron microscopy(TEM)is utilized to investigate the structure of Cu precipitates thermally formed in a high-strength low-alloy(HSLA)steel.The Cu precipitates were generally formed from solid solution and at the crystallographic defects such as martensite lath boundaries and dislocations.The Cu precipitates in the same aging condition have various structure of BCC,9 R and FCC,and the structural evolution does not greatly correlate with the actual sizes.The presence of different structures in an individual Cu precipitate is observed,which reflects the structural transformation occurring locally to relax the strain energy.The multiply additions in the steel possibly make the Cu precipitation more complex compared to the binary or the ternary Fe-Cu alloys with Ni or Mn additions.This research gives constructive suggestions on alloying design of Cu-bearing alloy steels.
基金This work was supported by the National Natural Science Foundation of China(No.50101009)
文摘Antibacterial activity of AISI420 stainless steel (SS) implanted by copper was investigated. Ions extracted from a metal vapor vacuum arc (MEVVA) are sourced with 100keV energy and a dose range from 0.2×1017 to 2.0×1017ions·cm-2. The saturation dose of Cu implantation in AISI420 SS and Cu surface concentration were calculated at the energy of 100keV. The effect of dose on the antibacterial activity was analyzed. Results of antibacterial test show that the saturation dose is the optimum implantation dose for best antibacterial activity, which is above 99% against both Escherichia coli and Staphylococcus aureus. Novel phases such as Fe4Cu3 and Cu9.9Fe0.1 were found in the implanted layer by glancing angle X-ray diffraction (GXRD). The antibacterial activity of AISI420 SS attributes to Cu-contained phase.
基金financially supported by the National Key Research and Development Program of China(13th Five-Year Plan)with the Contract No.2016YFB0300601the National High Technology Research and Development Program of China(No.2012AA03A508)。
文摘In this article,the influence of simulated thermal cycles for the heat-aff ected zone(HAZ)on the microstructural evolution and mechanical properties in a low-carbon high-strength Cu-bearing steel was investigated by microstructural characterization and mechanical tests.The results showed that the microstructure of the coarse-grained heat-aff ected zone(CGHAZ)and the fine-grained heat-aff ected zone(FGHAZ)was mainly comprised of lath martensite,and a mixed microstructure consisting of intercritical ferrite,tempered martensite and retained austenite occurred in the intercritically heat-aff ected zone(ICHAZ)and the subcritically heat-aff ected zone(SCHAZ).Also,8–11%retained austenite and more or less Cu precipitates were observed in the simulated HAZs except for CGHAZ.Charpy impact test indicated that the optimum toughness was obtained in FGHAZ,which was not only associated with grain refinement,but also correlated with deformation-induced transformation of the retained austenite,variant confi guration as interleaved type and a relatively weak variant selection.The toughness of ICHAZ and SCHAZ exhibited a slight downtrend due to the presence of Cu precipitates.The CGHAZ has the lowest toughness in the simulated HAZs,which was attributed to grain coarsening and heavy variant selection.In addition,the contribution of Cu precipitates to yield strength in simulated HAZs was estimated based on Russell–Brown model.It demonstrated an inverse variation trend to toughness.
