There remains growing interest in magnesium(Mg)and its alloys,as they are the lightest structural metallic materials and potential metallic biomaterials.In spite of the greatest historical Mg usage at present,the wide...There remains growing interest in magnesium(Mg)and its alloys,as they are the lightest structural metallic materials and potential metallic biomaterials.In spite of the greatest historical Mg usage at present,the wider use of Mg alloys remains restricted by the poor corrosion resistance.A nano amorphous film,as the composition of Al2O3,had now been deposited on the AZ31 Mg alloy substrate by atomic layer deposition(ALD).Grazing incidence X-ray diffraction(GIXRD),X-ray reflectivity(XRR),X-ray photoelectron spectroscopy(XPS),atomic force microscope(AFM)and scanning electron microscopy(SEM)had been employed to identify the chemical compositions,microstructure and Al2O3/Mg interface of specimens firstly.Then corrosion behavior had been evaluated by neutral salt spray test and electrochemical measurement.The results showed that nano amorphous film made a homogeneous cover on Mg alloy.The film could improve the corrosion resistance of Mg alloy greatly,not only with a positive shift in Ecorr and a decrease in icorr,but also with a more uniform corroded mode.Furthermore,the roughness was found to be an important factor for corrosion resistant,in the way that rougher surface was corroded worse,and greater improvement would be in corrosion resistant after nano amorphous film deposition.展开更多
A simple one-step anticorrosion Portland cement(PC)-based coating with an autogenerated oxide film on the surface of Mg alloy was successfully prepared in this study.The anticorrosion of coated Mg alloys was assessed ...A simple one-step anticorrosion Portland cement(PC)-based coating with an autogenerated oxide film on the surface of Mg alloy was successfully prepared in this study.The anticorrosion of coated Mg alloys was assessed by several electrochemical methods including open circuit potential,electrochemical impedance spectroscopy,and cyclic potentiodynamic polarization.The morphology and composition of PC-based coatings were characterized via scanning electron microscopy and X-ray diffraction.The composition of the autogenerated oxide film was analyzed via X-ray photoelectron spectroscopy.Results show that the PC-based coatings can significantly enhance the corrosion resistance of AZ41 Mg alloy due to the synergetic effect of PC-based coating and autogenerated oxide film.Particularly,the quality of oxide film plays a dominant role in determining anticorrosion of Mg alloy.Furthermore,the addition of metakaolin and dolomite enhances the resistance of PC-based coating and meanwhile,MoO_(4)^(2–)ions from PC-based coating can adsorb in the oxide film,improving the quality of the oxide film.展开更多
Cerium-based sealing treatment was developed for Mg-Al hydrotalcite film on AZ91D Mg alloy,and the influence of cerium salt solution was investigated to modify the surface integrity and corrosion resistance.Scanning e...Cerium-based sealing treatment was developed for Mg-Al hydrotalcite film on AZ91D Mg alloy,and the influence of cerium salt solution was investigated to modify the surface integrity and corrosion resistance.Scanning electron microscope(SEM)and X-ray diffraction(XRD)measurements were carried out to analyze the surface morphology and phase composition.The corrosion resistance of Mg-Al hydrotalcite film after sealing treatment was evaluated by the polarization curve and electrochemical impedance spectroscopy(EIS)tests.The results showed that lower concentration of Ce-containing solution was beneficial to seal the micro-cracks on Mg-Al hydrotalcite film,and improve the surface integrity and corrosion resistance;higher concentration of Ce-containing solution could seal fewer micro-cracks,and the corrosion resistance was decreased owing to the disintegration of Mg-Al hydrotalcite film.展开更多
In this study,the effects of Al addition on the corrosion behavior of pure Mg with controlled impurity contents were systematically analyzed according to the processing history.The results revealed that the corrosion ...In this study,the effects of Al addition on the corrosion behavior of pure Mg with controlled impurity contents were systematically analyzed according to the processing history.The results revealed that the corrosion behavior of high-purity Mg-Al alloys is strongly related to changes in the microstructure,including theβphase and Al-Mn or Al-Fe phases,and the protectiveness of the surface film according to the Al content and processing history.In the as-cast alloys,the corrosion rate increased due to the increase ofβphase as the Al content increased,but in the as-extruded alloys,the corrosion rate,which was high due to intermetallic compounds caused by impurities in the low Al alloy,decreased as the Al content increased,and then increased again.This is due to the combined effect of the increase of theβphase and decrease of the impurity effect,and the increase of the dissolved Al content.The results suggest that it is necessary to analyze the effect of alloying elements on the corrosion behavior of pure Mg with information concerning the impurity content and processing history.展开更多
The present study investigates the mechanical and in-vitro corrosion behavior of Mg-4Zn-0.5Ca-0.8Mn alloy in optimum homogenized conditions.The optimization of the homogenization parameters has been carried out employ...The present study investigates the mechanical and in-vitro corrosion behavior of Mg-4Zn-0.5Ca-0.8Mn alloy in optimum homogenized conditions.The optimization of the homogenization parameters has been carried out employing thermodynamic calculations and kinetic modeling.The model utilizes the inter-diffusivity of the solute elements and predicts that∼6–24 h of homogenization at 633 K effectively redistributes the elements in the Mg matrix.Based on the insights obtained from the simulations,the as-cast Mg-4Zn-0.5Ca-0.8Mn alloy was subjected to homogenization heat treatment process for 6–24h.The microstructural study through optical microscopy and scanning electron microscopy(SEM)revealed that the interconnected network of second phase precipitates substantially dissolve within 24 h,implying adequate homogenization.Moreover,fine Mg-Zn based precipitates with varied morphology and phase fractions also evolved during homogenization treatment,as confirmed through SEM and transmission electron microscopy.In the 12 h homogenized specimen,the highest fraction of uniformly dispersed fine precipitates resulted in the highest strength(∼225 MPa).On the other hand,a substantial disruption in coarse precipitate network and lower aspect ratio of fine Mg-Zn precipitates led to the highest ductility(∼8%)in this specimen.In the 24 h homogenized specimen,the ductility reduced marginally owing to higher aspect ratio of fine precipitates.The immersion and electrochemical tests(viz.,potentiodynamic polarization and electrochemical impedance spectroscopy)carried out in Hank’s solution revealed that the 24 h homogenized specimen exhibits the best corrosion properties.The least fraction of Ca_(2)Mg_(6)Zn_(3)phase with maximum disruption in interconnectivity,in combination with a small fraction of fine equilibrium MgZn_(2)precipitates,resulted in suppression of localized corrosion in this specimen.This promotes the formation of the most stable and compact product layer over the specimen,resulting in the highest corrosion resista展开更多
High reactivity and ease of ignition are the major obstacles for the application of Mg alloys in aerospace.Thus,the ignition mechanisms of Mg alloys should be investigated systematically,which can guide the ignition-p...High reactivity and ease of ignition are the major obstacles for the application of Mg alloys in aerospace.Thus,the ignition mechanisms of Mg alloys should be investigated systematically,which can guide the ignition-proof alloy design.This article concludes the factors influencing the ignition resistance of Mg alloys from oxide film and substrate microstructure,and also the mechanisms of alloying elements improving the ignition resistance.The low strength is another reason restricting the development of Mg alloys.Therefore,at the last section,Mg alloys with the combination of high strength and good ignition-proof performance are summarized,including Mg-Al-Ca based alloys,SEN(Mg-Al-Zn-Ca-Y)alloys as well as Mg-Y and Mg-Gd based alloys.Besides,the shortages and the future focus of theses alloys are also reviewed.The aim of this article is to promote the understanding of oxidation and ignition mechanisms of Mg alloys and to provide reference for the development of Mg alloys with high strength and excellent ignition-proof performance at the same time.展开更多
基金This work was supported by National Key Research and Development Program(Nos.2016YFB0701201,2016YFB0701203)National Natural Science Foundation of China(Nos.51671101)+3 种基金Domain Foundation of Equipment Advance Research of 13th Five-year Plan(No.61409220118)Natural Science Foundation of JiangXi Province(Nos.20171BCD40003)Key Research and Development Program of JiangXi Province(No GJJ150010)Nanchang University Graduate Innovation Special Fund(No.CX2018038).
文摘There remains growing interest in magnesium(Mg)and its alloys,as they are the lightest structural metallic materials and potential metallic biomaterials.In spite of the greatest historical Mg usage at present,the wider use of Mg alloys remains restricted by the poor corrosion resistance.A nano amorphous film,as the composition of Al2O3,had now been deposited on the AZ31 Mg alloy substrate by atomic layer deposition(ALD).Grazing incidence X-ray diffraction(GIXRD),X-ray reflectivity(XRR),X-ray photoelectron spectroscopy(XPS),atomic force microscope(AFM)and scanning electron microscopy(SEM)had been employed to identify the chemical compositions,microstructure and Al2O3/Mg interface of specimens firstly.Then corrosion behavior had been evaluated by neutral salt spray test and electrochemical measurement.The results showed that nano amorphous film made a homogeneous cover on Mg alloy.The film could improve the corrosion resistance of Mg alloy greatly,not only with a positive shift in Ecorr and a decrease in icorr,but also with a more uniform corroded mode.Furthermore,the roughness was found to be an important factor for corrosion resistant,in the way that rougher surface was corroded worse,and greater improvement would be in corrosion resistant after nano amorphous film deposition.
基金financial support from the National Key Research and Development Program of China(No.2021YFB3701100)the Natural Science Foundation Commission of China(Grant No.U20A20234 and 51874062)+2 种基金the Chongqing Foundation and Advanced Research Project(Grant No.cstc2019jcyjzdxmX0010)the Fundamental Research Funds for the Central Universities(No.2022CDJKYJH004C)the Science and Technology Major Project of Shanxi Province(No.20191102008).
文摘A simple one-step anticorrosion Portland cement(PC)-based coating with an autogenerated oxide film on the surface of Mg alloy was successfully prepared in this study.The anticorrosion of coated Mg alloys was assessed by several electrochemical methods including open circuit potential,electrochemical impedance spectroscopy,and cyclic potentiodynamic polarization.The morphology and composition of PC-based coatings were characterized via scanning electron microscopy and X-ray diffraction.The composition of the autogenerated oxide film was analyzed via X-ray photoelectron spectroscopy.Results show that the PC-based coatings can significantly enhance the corrosion resistance of AZ41 Mg alloy due to the synergetic effect of PC-based coating and autogenerated oxide film.Particularly,the quality of oxide film plays a dominant role in determining anticorrosion of Mg alloy.Furthermore,the addition of metakaolin and dolomite enhances the resistance of PC-based coating and meanwhile,MoO_(4)^(2–)ions from PC-based coating can adsorb in the oxide film,improving the quality of the oxide film.
基金supported by the National Natural Science Foundation of China(No.51701093)the Natural Science Foundation of Jiangsu Province(No.BK20170764)+2 种基金the Six Talent Peaks(No.2015-XCL-025)the Qing Lan Project of Jiangsu Province,the Practice Innovation Program for graduate students of Jiangsu Province(No.SJZZ16_0292)the Research Fund of Nanjing Institute of Technology(No.JCYJ201603).
文摘Cerium-based sealing treatment was developed for Mg-Al hydrotalcite film on AZ91D Mg alloy,and the influence of cerium salt solution was investigated to modify the surface integrity and corrosion resistance.Scanning electron microscope(SEM)and X-ray diffraction(XRD)measurements were carried out to analyze the surface morphology and phase composition.The corrosion resistance of Mg-Al hydrotalcite film after sealing treatment was evaluated by the polarization curve and electrochemical impedance spectroscopy(EIS)tests.The results showed that lower concentration of Ce-containing solution was beneficial to seal the micro-cracks on Mg-Al hydrotalcite film,and improve the surface integrity and corrosion resistance;higher concentration of Ce-containing solution could seal fewer micro-cracks,and the corrosion resistance was decreased owing to the disintegration of Mg-Al hydrotalcite film.
基金the main research program of the Korea Institute of Materials Science(Grant No.PNK8150)for financially supporting this study
文摘In this study,the effects of Al addition on the corrosion behavior of pure Mg with controlled impurity contents were systematically analyzed according to the processing history.The results revealed that the corrosion behavior of high-purity Mg-Al alloys is strongly related to changes in the microstructure,including theβphase and Al-Mn or Al-Fe phases,and the protectiveness of the surface film according to the Al content and processing history.In the as-cast alloys,the corrosion rate increased due to the increase ofβphase as the Al content increased,but in the as-extruded alloys,the corrosion rate,which was high due to intermetallic compounds caused by impurities in the low Al alloy,decreased as the Al content increased,and then increased again.This is due to the combined effect of the increase of theβphase and decrease of the impurity effect,and the increase of the dissolved Al content.The results suggest that it is necessary to analyze the effect of alloying elements on the corrosion behavior of pure Mg with information concerning the impurity content and processing history.
文摘The present study investigates the mechanical and in-vitro corrosion behavior of Mg-4Zn-0.5Ca-0.8Mn alloy in optimum homogenized conditions.The optimization of the homogenization parameters has been carried out employing thermodynamic calculations and kinetic modeling.The model utilizes the inter-diffusivity of the solute elements and predicts that∼6–24 h of homogenization at 633 K effectively redistributes the elements in the Mg matrix.Based on the insights obtained from the simulations,the as-cast Mg-4Zn-0.5Ca-0.8Mn alloy was subjected to homogenization heat treatment process for 6–24h.The microstructural study through optical microscopy and scanning electron microscopy(SEM)revealed that the interconnected network of second phase precipitates substantially dissolve within 24 h,implying adequate homogenization.Moreover,fine Mg-Zn based precipitates with varied morphology and phase fractions also evolved during homogenization treatment,as confirmed through SEM and transmission electron microscopy.In the 12 h homogenized specimen,the highest fraction of uniformly dispersed fine precipitates resulted in the highest strength(∼225 MPa).On the other hand,a substantial disruption in coarse precipitate network and lower aspect ratio of fine Mg-Zn precipitates led to the highest ductility(∼8%)in this specimen.In the 24 h homogenized specimen,the ductility reduced marginally owing to higher aspect ratio of fine precipitates.The immersion and electrochemical tests(viz.,potentiodynamic polarization and electrochemical impedance spectroscopy)carried out in Hank’s solution revealed that the 24 h homogenized specimen exhibits the best corrosion properties.The least fraction of Ca_(2)Mg_(6)Zn_(3)phase with maximum disruption in interconnectivity,in combination with a small fraction of fine equilibrium MgZn_(2)precipitates,resulted in suppression of localized corrosion in this specimen.This promotes the formation of the most stable and compact product layer over the specimen,resulting in the highest corrosion resista
基金the financial supports from the National Key Research and Development Plan(Grant No.2021YFB3701100)the National Natural Science Foundation of China(Grant No.U2241231,No.52071206)。
文摘High reactivity and ease of ignition are the major obstacles for the application of Mg alloys in aerospace.Thus,the ignition mechanisms of Mg alloys should be investigated systematically,which can guide the ignition-proof alloy design.This article concludes the factors influencing the ignition resistance of Mg alloys from oxide film and substrate microstructure,and also the mechanisms of alloying elements improving the ignition resistance.The low strength is another reason restricting the development of Mg alloys.Therefore,at the last section,Mg alloys with the combination of high strength and good ignition-proof performance are summarized,including Mg-Al-Ca based alloys,SEN(Mg-Al-Zn-Ca-Y)alloys as well as Mg-Y and Mg-Gd based alloys.Besides,the shortages and the future focus of theses alloys are also reviewed.The aim of this article is to promote the understanding of oxidation and ignition mechanisms of Mg alloys and to provide reference for the development of Mg alloys with high strength and excellent ignition-proof performance at the same time.
