Nano-zinc oxides(ZnO)demonstrate remarkable antibacterial properties.To further enhance the corrosion resistance and antibacterial efficiency of magnesium alloy micro-arc oxidation(MAO)coatings,this study investigates...Nano-zinc oxides(ZnO)demonstrate remarkable antibacterial properties.To further enhance the corrosion resistance and antibacterial efficiency of magnesium alloy micro-arc oxidation(MAO)coatings,this study investigates the preparation of ZnO-containing micro-arc oxidation coatings with dual functionality by incorporating nano-ZnO into MAO electrolyte.The influence of varying ZnO concentrations on the microstructure,corrosion resistance,and antibacterial properties of the coating was examined through microstructure analysis,immersion tests,electrochemical experiments,and antibacterial assays.The findings revealed that the addition of nano-ZnO significantly enhanced the corrosion resistance of the MAO-coated alloy.Specifically,when the ZnO concentration in the electrolyte was 5 g/L,the corrosion rate was more than ten times lower compared to the MAO coatings without ZnO.Moreover,the antibacterial efficacy of ZnO+MAO coating,prepared with a ZnO concentration of 5 g/L,surpassed 95%after 24 h of co-culturing with Staphylococcus aureus(S.aureus).The nano-ZnO+MAO-coated alloy exhibited exceptional degradation resistance,corrosion resistance,and antibacterial effectiveness.展开更多
An internal state variable(ISV)model was established according to the experimental results of hot plane strain compression(PSC)to predict the microstructure evolution during hot spinning of ZK61 alloy.The effects of t...An internal state variable(ISV)model was established according to the experimental results of hot plane strain compression(PSC)to predict the microstructure evolution during hot spinning of ZK61 alloy.The effects of the internal variables were considered in this ISV model,and the parameters were optimized by genetic algorithm.After validation,the ISV model was used to simulate the evolution of grain size(GS)and dynamic recrystallization(DRX)fraction during hot spinning via Abaqus and its subroutine Vumat.By comparing the simulated results with the experimental results,the application of the ISV model was proven to be reliable.Meanwhile,the strength of the thin-walled spun ZK61 tube increased from 303 to 334 MPa due to grain refinement by DRX and texture strengthening.Besides,some ultrafine grains(0.5μm)that played an important role in mechanical properties were formed due to the proliferation,movement,and entanglement of dislocations during the spinning process.展开更多
The excellent strength-ductility combination of hetero-grained Mg alloys has been reported to stem from pronounced hetero-deformation induced(HDI)stress.This stress alters the internal stress state of various slip sys...The excellent strength-ductility combination of hetero-grained Mg alloys has been reported to stem from pronounced hetero-deformation induced(HDI)stress.This stress alters the internal stress state of various slip systems and triggers significant activity of non-basal slips.However,the HDI stress state of different slip systems,and the mechanisms underlying the selective activation between basal and non-basal slips remain unclear to date.This study develops a novel HDI stress partitioning framework that in-situ calculates the crystallographic parameters and geometrical information of each datapoint within grains,aiming to reveal the correlation between HDI stress partitioning on individual slip systems and localized deformation model in the case of bimodal-grained ZK60 alloy.The framework demonstrates that HDI stress shows a strong dependence on the density of geometrically necessary dislocations(GNDs)and slip-system-level grain size,while exhibiting a relatively weaker correlation with equivalent-circle size of the hetero-grains.Given the close relation between the stress partitioning and the physical parameters,the framework can accurately predict the single and multiple slip activity fields obtained from highresolution digital image correlation(HR-DIC).This holds even for slip systems with low Schmid factors,which are theoretically difficult to activate.Using this framework,it is found that HDI stress plays a more prominent role in diminishing the effective resolved shear stress(RSS)of basaland prismatic(i.e.,component)dislocations,while having a negligible effect on pyramidal<c+a>slips.Benefiting from the increased ratio of RSS_(<c+a>)/RSS_(),pyramidal<c+a>dislocations are extensively activated,leading to excellent strength-ductility combination in the bimodal-grained ZK60 alloy.展开更多
The poor corrosion resistance of magnesium(Mg)and its alloys limits their application in various fields.Micro arc oxidation(MAO)coatings can improve the corrosion resistance,but the pore defects and low surface hardne...The poor corrosion resistance of magnesium(Mg)and its alloys limits their application in various fields.Micro arc oxidation(MAO)coatings can improve the corrosion resistance,but the pore defects and low surface hardness make them susceptible to wear and accelerated corrosion during usage.In this study,a ZrO_(2)nanoparticles doped-MAO coating is prepared on the ZK61 Mg alloy by utilizing an MgF_(2)passivation layer to prevent ablation.The ZrO_(2)nanoparticles re-melt and precipitate due to local discharging,which produces evenly dispersed nanocrystals in the MAO coating.As a result,the hardness of the MAO coating with the appropriate ZrO_(2)concentration increases by over 10 times,while the wear rate decreases and corrosion resistance increases.With increasing ZrO_(2)concentrations,the corrosion potentials increase from−1.528 V of the bare ZK61 Mg alloy to−1.184 V,the corrosion current density decreases from 1.065×10^(–4)A cm^(–2)to 3.960×10^(–8)A cm^(–2),and the charge transfer resistance increases from 3.41×10^(2)Ωcm^(2)to 6.782×10^(5)Ωcm^(2).Immersion tests conducted in a salt solution for 28 d reveal minimal corrosion in contrast to severe corrosion on the untreated ZK61 Mg alloy.ZrO_(2)nanoparticles improve the corrosion resistance of MAO coatings by sealing pores and secondary strengthening of the corrosion product layer.展开更多
基金supported by the National Natural Science Foundation of China(No.52001034)the China Postdoctoral Science Foundation(No.2023M731677)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX23_3032).
文摘Nano-zinc oxides(ZnO)demonstrate remarkable antibacterial properties.To further enhance the corrosion resistance and antibacterial efficiency of magnesium alloy micro-arc oxidation(MAO)coatings,this study investigates the preparation of ZnO-containing micro-arc oxidation coatings with dual functionality by incorporating nano-ZnO into MAO electrolyte.The influence of varying ZnO concentrations on the microstructure,corrosion resistance,and antibacterial properties of the coating was examined through microstructure analysis,immersion tests,electrochemical experiments,and antibacterial assays.The findings revealed that the addition of nano-ZnO significantly enhanced the corrosion resistance of the MAO-coated alloy.Specifically,when the ZnO concentration in the electrolyte was 5 g/L,the corrosion rate was more than ten times lower compared to the MAO coatings without ZnO.Moreover,the antibacterial efficacy of ZnO+MAO coating,prepared with a ZnO concentration of 5 g/L,surpassed 95%after 24 h of co-culturing with Staphylococcus aureus(S.aureus).The nano-ZnO+MAO-coated alloy exhibited exceptional degradation resistance,corrosion resistance,and antibacterial effectiveness.
基金supported by the National Natural Science Foundation of China(No.51905123)Major Scientific and Technological Innovation Program of Shandong Province,China(Nos.2020CXGC010303,2022ZLGX04)Key R&D Programme of Shandong Province,China(No.2022JMRH0308).
文摘An internal state variable(ISV)model was established according to the experimental results of hot plane strain compression(PSC)to predict the microstructure evolution during hot spinning of ZK61 alloy.The effects of the internal variables were considered in this ISV model,and the parameters were optimized by genetic algorithm.After validation,the ISV model was used to simulate the evolution of grain size(GS)and dynamic recrystallization(DRX)fraction during hot spinning via Abaqus and its subroutine Vumat.By comparing the simulated results with the experimental results,the application of the ISV model was proven to be reliable.Meanwhile,the strength of the thin-walled spun ZK61 tube increased from 303 to 334 MPa due to grain refinement by DRX and texture strengthening.Besides,some ultrafine grains(0.5μm)that played an important role in mechanical properties were formed due to the proliferation,movement,and entanglement of dislocations during the spinning process.
基金the National Natural Science Foundation of China(No.52305385,U23A20541,52471131,52201057)the University Natural Science Research Project of Anhui Province(No.2022AH050316).
文摘The excellent strength-ductility combination of hetero-grained Mg alloys has been reported to stem from pronounced hetero-deformation induced(HDI)stress.This stress alters the internal stress state of various slip systems and triggers significant activity of non-basal slips.However,the HDI stress state of different slip systems,and the mechanisms underlying the selective activation between basal and non-basal slips remain unclear to date.This study develops a novel HDI stress partitioning framework that in-situ calculates the crystallographic parameters and geometrical information of each datapoint within grains,aiming to reveal the correlation between HDI stress partitioning on individual slip systems and localized deformation model in the case of bimodal-grained ZK60 alloy.The framework demonstrates that HDI stress shows a strong dependence on the density of geometrically necessary dislocations(GNDs)and slip-system-level grain size,while exhibiting a relatively weaker correlation with equivalent-circle size of the hetero-grains.Given the close relation between the stress partitioning and the physical parameters,the framework can accurately predict the single and multiple slip activity fields obtained from highresolution digital image correlation(HR-DIC).This holds even for slip systems with low Schmid factors,which are theoretically difficult to activate.Using this framework,it is found that HDI stress plays a more prominent role in diminishing the effective resolved shear stress(RSS)of basaland prismatic(i.e.,component)dislocations,while having a negligible effect on pyramidal<c+a>slips.Benefiting from the increased ratio of RSS_(<c+a>)/RSS_(),pyramidal<c+a>dislocations are extensively activated,leading to excellent strength-ductility combination in the bimodal-grained ZK60 alloy.
基金supported by the Postdoctoral Fellowship Program of CPSF(No.GZC20231545)the China Postdoctoral Science Foundation(Nos.2024T170557 and 2023M742224)+6 种基金the Shanghai Post-doctoral Excellence Program(No.2023440)the National Natural Science Foundation of China(Nos.52127801,52401101,and 22205012)the Shenzhen Basic Research Project(Nos.JCYJ20210324120001003,JCYJ20200109144608205)the Guangdong Basic and Applied Basic Research Foundation(Nos.2020A1515011301 and 2021A1515012246)the IER Foundation(Nos.IERF202201 andIERF202202),the City University of Hong Kong Donation Research(No.DON-RMG 9229021)the Hong Kong PDFS-RGC Postdoctoral Fellowship Scheme(Nos.PDFS2122–1S08 and CityU 9061014)the Hong Kong HMRF(Health and Medical Research Fund)(Nos.2120972 and CityU 9211320).
文摘The poor corrosion resistance of magnesium(Mg)and its alloys limits their application in various fields.Micro arc oxidation(MAO)coatings can improve the corrosion resistance,but the pore defects and low surface hardness make them susceptible to wear and accelerated corrosion during usage.In this study,a ZrO_(2)nanoparticles doped-MAO coating is prepared on the ZK61 Mg alloy by utilizing an MgF_(2)passivation layer to prevent ablation.The ZrO_(2)nanoparticles re-melt and precipitate due to local discharging,which produces evenly dispersed nanocrystals in the MAO coating.As a result,the hardness of the MAO coating with the appropriate ZrO_(2)concentration increases by over 10 times,while the wear rate decreases and corrosion resistance increases.With increasing ZrO_(2)concentrations,the corrosion potentials increase from−1.528 V of the bare ZK61 Mg alloy to−1.184 V,the corrosion current density decreases from 1.065×10^(–4)A cm^(–2)to 3.960×10^(–8)A cm^(–2),and the charge transfer resistance increases from 3.41×10^(2)Ωcm^(2)to 6.782×10^(5)Ωcm^(2).Immersion tests conducted in a salt solution for 28 d reveal minimal corrosion in contrast to severe corrosion on the untreated ZK61 Mg alloy.ZrO_(2)nanoparticles improve the corrosion resistance of MAO coatings by sealing pores and secondary strengthening of the corrosion product layer.
