In the present study,to understand the mechanism of Mn on inhibiting Fe-caused Mg corrosion,the corrosion behaviour of commercial pure Mg and Mg-6 Mn alloy in 0.6 M NaCl solution is investigated.It is found that in Mg...In the present study,to understand the mechanism of Mn on inhibiting Fe-caused Mg corrosion,the corrosion behaviour of commercial pure Mg and Mg-6 Mn alloy in 0.6 M NaCl solution is investigated.It is found that in Mg-6 Mn alloy,Fe impurity is incorporated into Mn to form Mn(Fe)phase with Fe as solid solute.The initial galvanic corrosion cannot be reduced through converting Fe-rich phase to Mn(Fe)phase,since Mn(Fe)phase also has relatively strong cathodic activity and has much larger volume fraction than Fe-rich phase.However,the cathodic activation behaviour of pure Mg is inhibited.The cathodic activity even decreases for Mg-Mn alloy with increased exposure time,due to the reduced cathodic HER at the Mn(Fe)particles.Mn can be oxidized at the OCP of Mg-6 Mn alloy,resulting in relatively dense Mn-rich corrosion film on particle surface,which separates the particle from the electrolyte and,consequently,inhibits HER.展开更多
The influence of Fe2O3 impurity on the crystalline structure of cordierite synthesized from waste aluminum slag is discussed. XRD and SEM techniques were employed to characterize the crystalline structure and micros...The influence of Fe2O3 impurity on the crystalline structure of cordierite synthesized from waste aluminum slag is discussed. XRD and SEM techniques were employed to characterize the crystalline structure and microstructure of each specimen. Philips X’pert plus software was used to determine the lattice parameters of each specimen. The results show that the Fe2O3 content of 0.8~1.6wt% is beneficial to the formation of cordierite, with the cordierite amount reaching 90wt%. So 0.8~1.6wt% is considered as the allowable Fe2O3 content in the specimens and 0.8wt% is determined to be the best after overall analysis. Plus software analysis shows that the cordierite in each specimen has the same symmetrical hexagonal structure as the single crystal, and the lattice parameters as well as the lattice dimensions change slightly.展开更多
Modifying effect and mechanism of trace rare earth on Fe(Si) rich impurity phases in commercial purity aluminum were studied with the aids of SEM, EDAX, TEM, etc. It is found that Ce rich mixed rare earth (RE) is an...Modifying effect and mechanism of trace rare earth on Fe(Si) rich impurity phases in commercial purity aluminum were studied with the aids of SEM, EDAX, TEM, etc. It is found that Ce rich mixed rare earth (RE) is an effective modifying agent, which makes the coarse Fe rich impurity phases transform into complex compounds of tiny, sphere/short stick form, thus improving mechanical properties of this material; its modifying mechanism is in that RE gathering in front of solid/liquid interface enters into the impurity phases, forming complex (AlFeSiRE) compounds; or is adsorbed in the impurity phases surface, impeding the growth of impurity phases; however, excessive RE will result in the increasing of RE compounds (secondary phases), and plasticity reduction of this material. Therefore, its addition amount should be less than 0 07% (mass fraction).展开更多
The microstructure,extrusion texture and corrosion behavior of extruded dilute Mg–Al–Ca–Mn alloy with diferent Al contents were investigated.The corrosion rate of the alloy was more sensitive to the Fe impurities.T...The microstructure,extrusion texture and corrosion behavior of extruded dilute Mg–Al–Ca–Mn alloy with diferent Al contents were investigated.The corrosion rate of the alloy was more sensitive to the Fe impurities.The 1.2 wt%Al showed the lowest corrosion rate,which was mainly attributed to the weakening of the cathode efect caused by the increase of the Al and the decrease of the Fe in the precipitated phase.Refned grains,stronger basal surface texture and higher corrosion potential deriving from the higher Al content of the matrix also further enhanced the corrosion resistance of the matrix.展开更多
Removal feasibility of Fe impurity form La metal by electron beam melting(EBM) was analyzed,the removal mechanism was discussed,and the verification experiments were carried out in this study.The research results indi...Removal feasibility of Fe impurity form La metal by electron beam melting(EBM) was analyzed,the removal mechanism was discussed,and the verification experiments were carried out in this study.The research results indicate that,the evaporation coefficient of Fe in La metal is 35-175 at 1800-3000 K,and Fe impurity can be removed by EBM;the removal efficiency of Fe impurity is improved with the increasing EBM power,the Fe concentration is significantly decreased from 1482 to 0.1 μg/g under 50 kW and 2400 s;the reaction of Fe removal by EBM follows the first-order rate law,and Fe impurity is removed by evaporation as a single atom;transport from the La melt to the liquid boundary layer of the Fe atom is rate-controlling step in the EBM when the EBM power is 30-50 kW.展开更多
The microstructure and anti-corrosion behavior of Mg–Mn alloys by magnesium scrap have been investigated in this study.The results show that the size of the Fe-rich particles in magnesium scrap decreases but the quan...The microstructure and anti-corrosion behavior of Mg–Mn alloys by magnesium scrap have been investigated in this study.The results show that the size of the Fe-rich particles in magnesium scrap decreases but the quantity increases with the Mn addition.Although the presence of Mn-containing Fe-rich particles with unique symbiotic structure can eff ectively weaken the micro-galvanic corrosion,the presence of more free Fe(Fe-rich particles)does not necessarily lead to severe corrosion of the alloy.The corrosion susceptibility of Mg–Mn–Fe alloy primarily depends on the solubility of iron in the Mg matrix,while it can be significantly reduced by suitable Mn addition.Besides,the tolerance limit of the Fe impurity can be expressed as Femax=0.0083 Mn(relative to the iron solubility).Only when the Fe/Mn ratio is below 0.0083 can the alloy have excellent corrosion resistance,with the corrosion rate changing in the scope of 0.38±0.09 to 0.54±0.15 mg/cm^(2) day and icorr from 3 to 9×10^(–4) A/cm^(2).展开更多
基金financial support by the National Nature Science Foundation of China(No.51601036 and U1737102)the Fundamental Research Funds for the Central Universities(N170204010 and N162410002-2-4)Young Elite Scientists Sponsorship Program by CAST(2017QNRC001)
文摘In the present study,to understand the mechanism of Mn on inhibiting Fe-caused Mg corrosion,the corrosion behaviour of commercial pure Mg and Mg-6 Mn alloy in 0.6 M NaCl solution is investigated.It is found that in Mg-6 Mn alloy,Fe impurity is incorporated into Mn to form Mn(Fe)phase with Fe as solid solute.The initial galvanic corrosion cannot be reduced through converting Fe-rich phase to Mn(Fe)phase,since Mn(Fe)phase also has relatively strong cathodic activity and has much larger volume fraction than Fe-rich phase.However,the cathodic activation behaviour of pure Mg is inhibited.The cathodic activity even decreases for Mg-Mn alloy with increased exposure time,due to the reduced cathodic HER at the Mn(Fe)particles.Mn can be oxidized at the OCP of Mg-6 Mn alloy,resulting in relatively dense Mn-rich corrosion film on particle surface,which separates the particle from the electrolyte and,consequently,inhibits HER.
基金This work was supported by the '863' Project (2003AA322020)
文摘The influence of Fe2O3 impurity on the crystalline structure of cordierite synthesized from waste aluminum slag is discussed. XRD and SEM techniques were employed to characterize the crystalline structure and microstructure of each specimen. Philips X’pert plus software was used to determine the lattice parameters of each specimen. The results show that the Fe2O3 content of 0.8~1.6wt% is beneficial to the formation of cordierite, with the cordierite amount reaching 90wt%. So 0.8~1.6wt% is considered as the allowable Fe2O3 content in the specimens and 0.8wt% is determined to be the best after overall analysis. Plus software analysis shows that the cordierite in each specimen has the same symmetrical hexagonal structure as the single crystal, and the lattice parameters as well as the lattice dimensions change slightly.
文摘Modifying effect and mechanism of trace rare earth on Fe(Si) rich impurity phases in commercial purity aluminum were studied with the aids of SEM, EDAX, TEM, etc. It is found that Ce rich mixed rare earth (RE) is an effective modifying agent, which makes the coarse Fe rich impurity phases transform into complex compounds of tiny, sphere/short stick form, thus improving mechanical properties of this material; its modifying mechanism is in that RE gathering in front of solid/liquid interface enters into the impurity phases, forming complex (AlFeSiRE) compounds; or is adsorbed in the impurity phases surface, impeding the growth of impurity phases; however, excessive RE will result in the increasing of RE compounds (secondary phases), and plasticity reduction of this material. Therefore, its addition amount should be less than 0 07% (mass fraction).
基金supported by the National Natural Science Foundation of China(No.51804130)the Key Research and Development Projects of Science and Technology Development Plan of Jilin Province(No.20180201054GX)the Graduate Innovation Fund of Jilin University(Nos.101832020CX241,101832020CX242).
文摘The microstructure,extrusion texture and corrosion behavior of extruded dilute Mg–Al–Ca–Mn alloy with diferent Al contents were investigated.The corrosion rate of the alloy was more sensitive to the Fe impurities.The 1.2 wt%Al showed the lowest corrosion rate,which was mainly attributed to the weakening of the cathode efect caused by the increase of the Al and the decrease of the Fe in the precipitated phase.Refned grains,stronger basal surface texture and higher corrosion potential deriving from the higher Al content of the matrix also further enhanced the corrosion resistance of the matrix.
基金Project supported by the National Key Research and Development Program of China(2017YFB0405901)the National Natural Science Foundation of China(51504036,51604033)。
文摘Removal feasibility of Fe impurity form La metal by electron beam melting(EBM) was analyzed,the removal mechanism was discussed,and the verification experiments were carried out in this study.The research results indicate that,the evaporation coefficient of Fe in La metal is 35-175 at 1800-3000 K,and Fe impurity can be removed by EBM;the removal efficiency of Fe impurity is improved with the increasing EBM power,the Fe concentration is significantly decreased from 1482 to 0.1 μg/g under 50 kW and 2400 s;the reaction of Fe removal by EBM follows the first-order rate law,and Fe impurity is removed by evaporation as a single atom;transport from the La melt to the liquid boundary layer of the Fe atom is rate-controlling step in the EBM when the EBM power is 30-50 kW.
基金financially supported by the National Key Research and Development Program of China(No.2016YFB0301100)the Fundamental Research Funds for the Central Universities(No.2018CDJDCD0001)the Key Nature Science Foundation of Chongqing(No cstc2017jcyjBX0040)。
文摘The microstructure and anti-corrosion behavior of Mg–Mn alloys by magnesium scrap have been investigated in this study.The results show that the size of the Fe-rich particles in magnesium scrap decreases but the quantity increases with the Mn addition.Although the presence of Mn-containing Fe-rich particles with unique symbiotic structure can eff ectively weaken the micro-galvanic corrosion,the presence of more free Fe(Fe-rich particles)does not necessarily lead to severe corrosion of the alloy.The corrosion susceptibility of Mg–Mn–Fe alloy primarily depends on the solubility of iron in the Mg matrix,while it can be significantly reduced by suitable Mn addition.Besides,the tolerance limit of the Fe impurity can be expressed as Femax=0.0083 Mn(relative to the iron solubility).Only when the Fe/Mn ratio is below 0.0083 can the alloy have excellent corrosion resistance,with the corrosion rate changing in the scope of 0.38±0.09 to 0.54±0.15 mg/cm^(2) day and icorr from 3 to 9×10^(–4) A/cm^(2).