The surface properties of weathering steel(WS)is very important for its service performance and safety,and the localized corrosion induced by inclusions is closely related to the surface properties of WS and its appli...The surface properties of weathering steel(WS)is very important for its service performance and safety,and the localized corrosion induced by inclusions is closely related to the surface properties of WS and its application.In the current work,a common spherical(Al,Mg,Ca,Mn)-oxy-sulfide inclusion was selected to investigate the corrosion evolution of complex inclusion and its effect on localized corrosion on WS surface.The results indicate the inclusion in WS consists of(Ca,Mn)sulfides part and(Ca,Al,Mg)oxides part with complex core-shell structure.Locally preferential dissolution occurs in(Ca,Mn)sulfides part as well as metal matrix around the inclusions.Furthermore,both parts of the inclusions with poor conductivity and high-density dislocation at metal matrix around the inclusions was found,which suggests that traditional micro-galvanic corrosion cell may not be the cause of inclusion-induced localized corrosion on WS surface at initial stage of corrosion.The variation in maximum and average depth around the inclusion or selected region with immersion time indicates that localized corrosion induced by inclusions is overwhelmed by uniform corrosion of WS in the latter stage of immersion,then the rust formed on WS surface consists of two layers.展开更多
The microstructure and corrosion behavior of Al-Zn-Mg alloy(namely 7×××)after natural aging treatment(NAT)and artificial aging treatment(AAT)in aqueous NaCl solutions containing different aggressive ion...The microstructure and corrosion behavior of Al-Zn-Mg alloy(namely 7×××)after natural aging treatment(NAT)and artificial aging treatment(AAT)in aqueous NaCl solutions containing different aggressive ions have been investigated in current work.Results of microstructure characterization demonstrate that the aging treatment has a great influence on the grain size and precipitates.The grain size is relatively sizeable and no evident precipitates are observed in alloy after NAT comparable with that after AAT.The electrochemical corrosion behavior of alloy was studied by polarization curve and electrochemical impedance spectroscopy(EIS).The corrosion potential(E_(corr))of the aluminum alloy is more negative in 3.5 wt.%NaCl containing 0.052 wt.%NaHSO_(3)solution than that in 3.5 wt.%NaCl solutions with or without 0.907 wt.%NaHCO_(3).Charge transfer resistance(Rct)results reveal that alloy after AAT has an enhancement of corrosion resistance compare with that after NAT.With the immersion time increasing,mostly pitting spreads over the surface of the alloy only in NaCl solution,whereas exfoliation corrosion mainly occurs in NaCl solutions containing NaHSO_(3)or NaHCO_(3).展开更多
The corrosion behavior of zinc and its alloy under thin electrolyte layers （TEL） in 0.1M NaC1 solution was investigated by cathodic polarization curves and EIS. There was only one phase in pure zinc while zinc alloy...The corrosion behavior of zinc and its alloy under thin electrolyte layers （TEL） in 0.1M NaC1 solution was investigated by cathodic polarization curves and EIS. There was only one phase in pure zinc while zinc alloy consisted of eutectic phase and primary phase. Corrosion rate of zinc alloy was faster than that of pure zinc due to the effect of the micro-galvanic couples between the primary phase and the eutectic phase. The results indicated that corrosion rate of zinc alloy was greatly enhanced under TEL than that in bulk solution. Pure zinc exhibited minimum corrosion resistance as TEL decreased to 198 #m. Zinc and its alloy exhibited localized corrosion under TEL while it was more uniform in bulk solution. There were two capacitive loops in high frequency （HF） and middle frequency （MF） respectively, with finite length diffusion in low frequency （LF） presented in EIS. For pure zinc under TEL below 300 pm an additional inductive loop presented in MF-LF. The corrosion products and morphology were respectively examined by X-ray diffraction （XRD）, FTIR （Fourier Transform Infra Red） and SEM-EDS. FTIR micro spectroscopy results indicated that the component of the corrosion products was similar at different section of the specimen surface but different in content.展开更多
By using thermo-mechanical processing,99.996 wt.%pure Ni with different grain boundary characteristics were fabricated(Sample#1,700℃×10 h+cold rolling reduction 50%+650℃×2 h;Sample#2,700℃×10 h+cold r...By using thermo-mechanical processing,99.996 wt.%pure Ni with different grain boundary characteristics were fabricated(Sample#1,700℃×10 h+cold rolling reduction 50%+650℃×2 h;Sample#2,700℃×10 h+cold rolling reduction 50%+900℃×5 min).Hydrogen embrittlement sensitivity of the two samples was determined by using high-pressure hydrogen charging,low strain rate tensile test and SEM fractography.Compared with Sample#1,hydrogen embrittlement index of Sample#2 increased from 0.52 to 0.71.The effects of grain size,grain boundary type and grain boundary curviness on hydrogen embrittlement of pure Ni were discussed.The results indicate that:1)special grain boundaries including twin grain boundaries may have a marginal effect on tailoring hydrogen embrittlement resistance in pure Ni;2)increasing grain boundary curviness is an effective way to improve hydrogen embrittlement resistance of Ni.展开更多
Microstructure,thermal stability at room temperature and corrosion behavior of ultrasonic shot peened AA7034were investigated in this work.Microstructure modification induced by ultrasonic shot peening was obtained by...Microstructure,thermal stability at room temperature and corrosion behavior of ultrasonic shot peened AA7034were investigated in this work.Microstructure modification induced by ultrasonic shot peening was obtained by using OM,SEM,EBSD and XRD,and it was found that a~200μm thick gradient surface layer with nanoscale grains on the topmost layer was induced on the peened sample.XRD peaks of the pre-existing aginginduced precipitates,i.e.,η′andηphases,disappeared after peening and did not show up during 52 monthslong natural aging treatment,showing good thermal stability at room temperature.After peening,a significant improvement in intergranular corrosion resistance is evident.Electrochemical characterizations like open circuit potential and electrochemical impedance spectroscopy were conducted on various depths of the peened sample and the results indicated that uniform corrosion rate was largely accelerated by the presence of foreign Ferich contamination,implying that modifications should be made to reduce/avoid the foreign contamination.Additionally,mechanisms of corrosion improvement and good thermal stability of the nanocrystalline surface layer of AA7304 are also discussed.展开更多
基金financially supported by the National Key Research and Development Program of China(No.2017YFB0702302)the National Natural Science Foundation of China(No.51771174)the National Materials Corrosion and Protection Data Center。
文摘The surface properties of weathering steel(WS)is very important for its service performance and safety,and the localized corrosion induced by inclusions is closely related to the surface properties of WS and its application.In the current work,a common spherical(Al,Mg,Ca,Mn)-oxy-sulfide inclusion was selected to investigate the corrosion evolution of complex inclusion and its effect on localized corrosion on WS surface.The results indicate the inclusion in WS consists of(Ca,Mn)sulfides part and(Ca,Al,Mg)oxides part with complex core-shell structure.Locally preferential dissolution occurs in(Ca,Mn)sulfides part as well as metal matrix around the inclusions.Furthermore,both parts of the inclusions with poor conductivity and high-density dislocation at metal matrix around the inclusions was found,which suggests that traditional micro-galvanic corrosion cell may not be the cause of inclusion-induced localized corrosion on WS surface at initial stage of corrosion.The variation in maximum and average depth around the inclusion or selected region with immersion time indicates that localized corrosion induced by inclusions is overwhelmed by uniform corrosion of WS in the latter stage of immersion,then the rust formed on WS surface consists of two layers.
基金financially supported by the National Key R&D Program of China(No.2017YFB0702302)the National Natural Science Foundation of China(No.51771174)the National Materials Corrosion and Protection Data Center。
文摘The microstructure and corrosion behavior of Al-Zn-Mg alloy(namely 7×××)after natural aging treatment(NAT)and artificial aging treatment(AAT)in aqueous NaCl solutions containing different aggressive ions have been investigated in current work.Results of microstructure characterization demonstrate that the aging treatment has a great influence on the grain size and precipitates.The grain size is relatively sizeable and no evident precipitates are observed in alloy after NAT comparable with that after AAT.The electrochemical corrosion behavior of alloy was studied by polarization curve and electrochemical impedance spectroscopy(EIS).The corrosion potential(E_(corr))of the aluminum alloy is more negative in 3.5 wt.%NaCl containing 0.052 wt.%NaHSO_(3)solution than that in 3.5 wt.%NaCl solutions with or without 0.907 wt.%NaHCO_(3).Charge transfer resistance(Rct)results reveal that alloy after AAT has an enhancement of corrosion resistance compare with that after NAT.With the immersion time increasing,mostly pitting spreads over the surface of the alloy only in NaCl solution,whereas exfoliation corrosion mainly occurs in NaCl solutions containing NaHSO_(3)or NaHCO_(3).
基金supported by National Natural Science Foundation of China(Nos.50801056 and J0830413)the National R&D Infrastructure and Facility Development Program of China (No.2005DKA10400-Z20)the Zijin Project of Zhejiang University
文摘The corrosion behavior of zinc and its alloy under thin electrolyte layers （TEL） in 0.1M NaC1 solution was investigated by cathodic polarization curves and EIS. There was only one phase in pure zinc while zinc alloy consisted of eutectic phase and primary phase. Corrosion rate of zinc alloy was faster than that of pure zinc due to the effect of the micro-galvanic couples between the primary phase and the eutectic phase. The results indicated that corrosion rate of zinc alloy was greatly enhanced under TEL than that in bulk solution. Pure zinc exhibited minimum corrosion resistance as TEL decreased to 198 #m. Zinc and its alloy exhibited localized corrosion under TEL while it was more uniform in bulk solution. There were two capacitive loops in high frequency （HF） and middle frequency （MF） respectively, with finite length diffusion in low frequency （LF） presented in EIS. For pure zinc under TEL below 300 pm an additional inductive loop presented in MF-LF. The corrosion products and morphology were respectively examined by X-ray diffraction （XRD）, FTIR （Fourier Transform Infra Red） and SEM-EDS. FTIR micro spectroscopy results indicated that the component of the corrosion products was similar at different section of the specimen surface but different in content.
基金financially supported by the Youth Innovation Project Funded by the Education Department of Guangdong Province(No.2018KQNCX227)the National Natural Science Foundation of China(Nos.52101115,51901098 and 52071347)
文摘By using thermo-mechanical processing,99.996 wt.%pure Ni with different grain boundary characteristics were fabricated(Sample#1,700℃×10 h+cold rolling reduction 50%+650℃×2 h;Sample#2,700℃×10 h+cold rolling reduction 50%+900℃×5 min).Hydrogen embrittlement sensitivity of the two samples was determined by using high-pressure hydrogen charging,low strain rate tensile test and SEM fractography.Compared with Sample#1,hydrogen embrittlement index of Sample#2 increased from 0.52 to 0.71.The effects of grain size,grain boundary type and grain boundary curviness on hydrogen embrittlement of pure Ni were discussed.The results indicate that:1)special grain boundaries including twin grain boundaries may have a marginal effect on tailoring hydrogen embrittlement resistance in pure Ni;2)increasing grain boundary curviness is an effective way to improve hydrogen embrittlement resistance of Ni.
基金financially supported by the Open Research Fund of Songshan Lake Materials Laboratory(No.2021SLABFN13)the National Natural Science Foundation of China(Nos.52101115 and 52071347)the Guangdong Basic and Applied Basic Research Foundation(No.2023A1515010113)
文摘Microstructure,thermal stability at room temperature and corrosion behavior of ultrasonic shot peened AA7034were investigated in this work.Microstructure modification induced by ultrasonic shot peening was obtained by using OM,SEM,EBSD and XRD,and it was found that a~200μm thick gradient surface layer with nanoscale grains on the topmost layer was induced on the peened sample.XRD peaks of the pre-existing aginginduced precipitates,i.e.,η′andηphases,disappeared after peening and did not show up during 52 monthslong natural aging treatment,showing good thermal stability at room temperature.After peening,a significant improvement in intergranular corrosion resistance is evident.Electrochemical characterizations like open circuit potential and electrochemical impedance spectroscopy were conducted on various depths of the peened sample and the results indicated that uniform corrosion rate was largely accelerated by the presence of foreign Ferich contamination,implying that modifications should be made to reduce/avoid the foreign contamination.Additionally,mechanisms of corrosion improvement and good thermal stability of the nanocrystalline surface layer of AA7304 are also discussed.
