A modified electrolyte （CH3COOH-HClO4-A-B） for electropolishing （EP） of NiTi was presented for improving the corrosion resistance and biocompatibility of the alloy. Using the proposed parameters, a homogeneous and...A modified electrolyte （CH3COOH-HClO4-A-B） for electropolishing （EP） of NiTi was presented for improving the corrosion resistance and biocompatibility of the alloy. Using the proposed parameters, a homogeneous and uniform surface was obtained. Atomic force microscopy （AFM） revealed that the surface roughness （Ra） for EP sample （23.21 nm） was close to mechanical polishing （MP） sample （19.36 nm）. Analysis by X-ray photoelectron spectroscopy （XPS） showed that Ti/Ni ratio increased from 3.1 for MP sample to 27.6 for EP sample. Measurements using potentiodynamic polarization in Hanks＇ solution showed that no pitting occurred for EP sample even though the applied potential increased up to 1500 mV （vs SCE）, while the MP sample was broken down at 650 mV. The present study indicates that electropolishing NiTi with this modified electrolyte contributes to the improved biocompatibility of NiTi.展开更多
Electron beam melting(EBM),as an excellent Additive Manufacturing(AM)technology,enables the printing of Ti-6Al-4V alloy for a wide range of applications such as aerospace and biomechanical industries.It improves funct...Electron beam melting(EBM),as an excellent Additive Manufacturing(AM)technology,enables the printing of Ti-6Al-4V alloy for a wide range of applications such as aerospace and biomechanical industries.It improves functionality and integrity of components and negates complexities in assembly processes.However,due to the poor surface and sub-surface integrity represented by the rough surface finish and low dimensional accuracy,achieving a favorable surface condition is quite challenging.Therefore,post processing becomes essential for these electron beam melted(EBM-ed)Ti-6Al-4V alloys.Being the most common technique to improve such parts,milling of Ti-6Al-4V alloy is very challenging and resulting tool wear issues,due to its unique material properties.Thus,this paper presents a comprehensive study on the surface integrity of EBM-ed Ti-6Al-4V parts processed by precision grinding and electropolishing,aiming to qualitatively and quantitatively clarify the interrelation between process parameters and processed surface quality.The surface and subsurface characteristics such as profile accuracy,surface roughness,microstructure,defective layer and residual stress before and after post processing were compared and evaluated.The results show that by precision grinding,the profile accuracy was improved from over 300μm PV to 7μm PV,while surface roughness(R_(a))was reduced from 30μm to about 2μm.The layer with partially melt particles was removed,but introduced a deformed subsurface layer with more residual stress.Then by applying electropolishing,the residual stress was released and the deformed layer was removed.In addition,Ra was further reduced to 0.65μm.The research can serve as a reference for the integration of post machining processes with AM.展开更多
The electrochemical behaviours of titanium alloy Ti-10V-2Fe-3Al after electropolishing in a self-developed electrolyte in comparison with conventional grinding were studied by electrochemical impedance spectroscopy （...The electrochemical behaviours of titanium alloy Ti-10V-2Fe-3Al after electropolishing in a self-developed electrolyte in comparison with conventional grinding were studied by electrochemical impedance spectroscopy （EIS）.Optical microscopy （OM）,scanning electron microscopy （SEM）,atomic force microscopy （AFM） and X-ray photoelectron spectroscopy （XPS） were used to evaluate the surface characteristics of the alloy.It was found from the EIS experiments that the polarization resistance （Rp） was increased,the double layer capacitance （Qc） was decreased and the electrochemical impedance of the alloy was enhanced by electropolishing.The electropolished surface was flat,smooth and bright and its roughness was 3.310 nm.To underline the advantage of electropolishing process against grinding to provide the anodic oxidation process with a higher quality substrate,the ground and electropolished titanium alloys were anodized in parallel under the same conditions.The corrosion behaviours of the two kinds of anodized titanium alloys were compared.It was revealed that electropolishing generated a high quality substrate and improved the corrosion resistance of anodic oxide film formed on titanium alloy Ti-10V-2Fe-3Al.Furthermore,the mechanism of electropolishing improving the corrosion resistance of the anodic oxide film was proposed.展开更多
3D metal printing process has attracted increasing attention in recent years due to advantages,such as flexibility and rapid prototyping.This study aims to investigate the orientation effect of electropolishing charac...3D metal printing process has attracted increasing attention in recent years due to advantages,such as flexibility and rapid prototyping.This study aims to investigate the orientation effect of electropolishing characteristics on different surfaces of 316L stainless steel fabricated by laser powder bed fusion(L-PBF),considering that the rough surface of 3D printed parts is a key factor limiting its applications in the industry.The electropolishing characteristics on the different surfaces corresponding to the building orientation in selective laser melting are studied.Experimental results show that electrolyte temperature has critical importance on the electropolishing,especially for the vertical direction to the layering plane.The finish of electropolished surfaces is affected by the defects generated during L-PBF process.Thus,the electropolished vertical surface has higher surface roughness Sa than the horizontal surface.The X-ray photoelectron spectroscopy spectra show that the electropolished horizontal surface has higher Cr/Fe element ratio than the vertical surface.The electropolished horizontal surface presents higher corrosion resistance than the vertical surface by measuring the anodic polarization curves and fitting the equivalent circuit of experimental electrochemical impedance spectroscopy.展开更多
Titanium(Ti) alloys are widely used in aerospace industry due to the low density and high corrosion resistance. However, machining and polishing remain great challenges because of the hardness and chemical stability. ...Titanium(Ti) alloys are widely used in aerospace industry due to the low density and high corrosion resistance. However, machining and polishing remain great challenges because of the hardness and chemical stability. With a home-made electrochemical machining workstation, cyclic voltammetry is performed at a wide potential range of [0 V, 20 V] to record the details of passivation and depassivation processes under a hydrodynamic mode. The results show that the thickness of viscous layer formed on the alloy surface plays a crucial effect on the electropolishing quality. The technical parameters, including the mechanical motion rate, polishing time and electrode gap, are optimized to achieve a surface roughness less than 1.9 nm, which shows a prospective application in the electrochemical machining of Ti and it alloys.展开更多
Two 650 MHz single-cell superconducting radio-frequency(SRF)cavities used for the Circular Electron Positron Collider(CEPC)were studied to achieve a high accelerating gradient(E_(acc))and high intrinsic quality factor...Two 650 MHz single-cell superconducting radio-frequency(SRF)cavities used for the Circular Electron Positron Collider(CEPC)were studied to achieve a high accelerating gradient(E_(acc))and high intrinsic quality factor(Q_(0)).The 650 MHz single-cell cavities were subjected to a combination of buffered chemical polishing(BCP)and electropolishing(EP),and their E_(acc) exceeded40 MV/m.Such a high E_(acc) may result from the cold EP with more uniform removal.BCP is easy,cheap,and rough,whereas EP is complicated,expensive,and precise Therefore,the combination of BCP and EP investigated in this study is suitable for surface treatments of mass SRF cavities.Medium temperature(mid-T)furnace baking was also conducted,which demonstrated an ultrahigh Q_(0) of 8×10^(10) at 22 MV/m for both cavities,and an extremely low BCS resistance(R_(BCS))of~1.0 nΩwas achieved a2.0 K.展开更多
Transmission electron microscopy （TEM） is usually used to identify the amorphicity. However, some artifacts may be introduced due to improper TEM foil preparation. In this paper, three Al-rich metallic glasses with ...Transmission electron microscopy （TEM） is usually used to identify the amorphicity. However, some artifacts may be introduced due to improper TEM foil preparation. In this paper, three Al-rich metallic glasses with and without a glass transition were selected for characterizing the effect of the electropolishing condition on the as-quenched structure during TEM specimen preparation. It is shown that the occurrence of the modulated bright-dark structure under TEM observation is closely sensitive to the electropolishing condition, which suggests us being careful about the possible artifacts induced by specimen preparation when examining amorphous alloys under TEM.展开更多
A porous anodic alumina (PAA) film has been investigated to realise highly-ordered nano-porous structures. A two-step anodization process is used to anodize aluminium into size-controllable aluminium oxide. In this pa...A porous anodic alumina (PAA) film has been investigated to realise highly-ordered nano-porous structures. A two-step anodization process is used to anodize aluminium into size-controllable aluminium oxide. In this paper, we investigate how anodization parameters affect nano-porous structures, such as voltage and time of pretreatment, anodization voltage and time, pore widening time. The results showed pretreatment is important to obtain a smooth surface for anodizing. The pore size is controllable between 30 and 80 nm, with a linear fit curve. The interpore size is constant at around 95 nm, and the pore densities are between 1010 and 1011 cm–2. The formation of straight vertical walls is crucial if the PAA film is to be subsequently used as the template for the growth of metal nanowire arrays.展开更多
文摘A modified electrolyte （CH3COOH-HClO4-A-B） for electropolishing （EP） of NiTi was presented for improving the corrosion resistance and biocompatibility of the alloy. Using the proposed parameters, a homogeneous and uniform surface was obtained. Atomic force microscopy （AFM） revealed that the surface roughness （Ra） for EP sample （23.21 nm） was close to mechanical polishing （MP） sample （19.36 nm）. Analysis by X-ray photoelectron spectroscopy （XPS） showed that Ti/Ni ratio increased from 3.1 for MP sample to 27.6 for EP sample. Measurements using potentiodynamic polarization in Hanks＇ solution showed that no pitting occurred for EP sample even though the applied potential increased up to 1500 mV （vs SCE）, while the MP sample was broken down at 650 mV. The present study indicates that electropolishing NiTi with this modified electrolyte contributes to the improved biocompatibility of NiTi.
基金financial support from LiaoNing Revitalization Talents Program(No.XLYC1807230)A*STAR Industrial Additive Manufacturing Program:Work Package 3(Electron Beam Melting,No.1325504103)Liaoning Natural Science Foundation Guidance Plan(No.20180550171)。
文摘Electron beam melting(EBM),as an excellent Additive Manufacturing(AM)technology,enables the printing of Ti-6Al-4V alloy for a wide range of applications such as aerospace and biomechanical industries.It improves functionality and integrity of components and negates complexities in assembly processes.However,due to the poor surface and sub-surface integrity represented by the rough surface finish and low dimensional accuracy,achieving a favorable surface condition is quite challenging.Therefore,post processing becomes essential for these electron beam melted(EBM-ed)Ti-6Al-4V alloys.Being the most common technique to improve such parts,milling of Ti-6Al-4V alloy is very challenging and resulting tool wear issues,due to its unique material properties.Thus,this paper presents a comprehensive study on the surface integrity of EBM-ed Ti-6Al-4V parts processed by precision grinding and electropolishing,aiming to qualitatively and quantitatively clarify the interrelation between process parameters and processed surface quality.The surface and subsurface characteristics such as profile accuracy,surface roughness,microstructure,defective layer and residual stress before and after post processing were compared and evaluated.The results show that by precision grinding,the profile accuracy was improved from over 300μm PV to 7μm PV,while surface roughness(R_(a))was reduced from 30μm to about 2μm.The layer with partially melt particles was removed,but introduced a deformed subsurface layer with more residual stress.Then by applying electropolishing,the residual stress was released and the deformed layer was removed.In addition,Ra was further reduced to 0.65μm.The research can serve as a reference for the integration of post machining processes with AM.
基金Funded by the National Natural Science Foundation of China(No.51001007)
文摘The electrochemical behaviours of titanium alloy Ti-10V-2Fe-3Al after electropolishing in a self-developed electrolyte in comparison with conventional grinding were studied by electrochemical impedance spectroscopy （EIS）.Optical microscopy （OM）,scanning electron microscopy （SEM）,atomic force microscopy （AFM） and X-ray photoelectron spectroscopy （XPS） were used to evaluate the surface characteristics of the alloy.It was found from the EIS experiments that the polarization resistance （Rp） was increased,the double layer capacitance （Qc） was decreased and the electrochemical impedance of the alloy was enhanced by electropolishing.The electropolished surface was flat,smooth and bright and its roughness was 3.310 nm.To underline the advantage of electropolishing process against grinding to provide the anodic oxidation process with a higher quality substrate,the ground and electropolished titanium alloys were anodized in parallel under the same conditions.The corrosion behaviours of the two kinds of anodized titanium alloys were compared.It was revealed that electropolishing generated a high quality substrate and improved the corrosion resistance of anodic oxide film formed on titanium alloy Ti-10V-2Fe-3Al.Furthermore,the mechanism of electropolishing improving the corrosion resistance of the anodic oxide film was proposed.
基金This publication has emanated from research supported in part by a grant from Science Foundation Ireland under Grant No.15/RP/B3208For the purpose of Open Access,the author has applied a CC BY public copyright license to any Author Accepted Manuscript version arising from this submissionThis project has also received funding from the Enterprise Ireland and the European Union's Horizon 2020 Research and Innovation Program under the Marie Sklodowska-Curie Grant agreement No.713654.
文摘3D metal printing process has attracted increasing attention in recent years due to advantages,such as flexibility and rapid prototyping.This study aims to investigate the orientation effect of electropolishing characteristics on different surfaces of 316L stainless steel fabricated by laser powder bed fusion(L-PBF),considering that the rough surface of 3D printed parts is a key factor limiting its applications in the industry.The electropolishing characteristics on the different surfaces corresponding to the building orientation in selective laser melting are studied.Experimental results show that electrolyte temperature has critical importance on the electropolishing,especially for the vertical direction to the layering plane.The finish of electropolished surfaces is affected by the defects generated during L-PBF process.Thus,the electropolished vertical surface has higher surface roughness Sa than the horizontal surface.The X-ray photoelectron spectroscopy spectra show that the electropolished horizontal surface has higher Cr/Fe element ratio than the vertical surface.The electropolished horizontal surface presents higher corrosion resistance than the vertical surface by measuring the anodic polarization curves and fitting the equivalent circuit of experimental electrochemical impedance spectroscopy.
基金supported by the National Natural Science Foundation of China (91323303, 21327002, 21573054, 21321062)
文摘Titanium(Ti) alloys are widely used in aerospace industry due to the low density and high corrosion resistance. However, machining and polishing remain great challenges because of the hardness and chemical stability. With a home-made electrochemical machining workstation, cyclic voltammetry is performed at a wide potential range of [0 V, 20 V] to record the details of passivation and depassivation processes under a hydrodynamic mode. The results show that the thickness of viscous layer formed on the alloy surface plays a crucial effect on the electropolishing quality. The technical parameters, including the mechanical motion rate, polishing time and electrode gap, are optimized to achieve a surface roughness less than 1.9 nm, which shows a prospective application in the electrochemical machining of Ti and it alloys.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB25000000)the National Natural Science Foundation of China(No.12075270)the Platform of Advanced Photon Source Technology R&D。
文摘Two 650 MHz single-cell superconducting radio-frequency(SRF)cavities used for the Circular Electron Positron Collider(CEPC)were studied to achieve a high accelerating gradient(E_(acc))and high intrinsic quality factor(Q_(0)).The 650 MHz single-cell cavities were subjected to a combination of buffered chemical polishing(BCP)and electropolishing(EP),and their E_(acc) exceeded40 MV/m.Such a high E_(acc) may result from the cold EP with more uniform removal.BCP is easy,cheap,and rough,whereas EP is complicated,expensive,and precise Therefore,the combination of BCP and EP investigated in this study is suitable for surface treatments of mass SRF cavities.Medium temperature(mid-T)furnace baking was also conducted,which demonstrated an ultrahigh Q_(0) of 8×10^(10) at 22 MV/m for both cavities,and an extremely low BCS resistance(R_(BCS))of~1.0 nΩwas achieved a2.0 K.
基金This work was financially supported by the National Natural Science Foundation of China （Nos. 50271070, 50323009, 50471076）.
文摘Transmission electron microscopy （TEM） is usually used to identify the amorphicity. However, some artifacts may be introduced due to improper TEM foil preparation. In this paper, three Al-rich metallic glasses with and without a glass transition were selected for characterizing the effect of the electropolishing condition on the as-quenched structure during TEM specimen preparation. It is shown that the occurrence of the modulated bright-dark structure under TEM observation is closely sensitive to the electropolishing condition, which suggests us being careful about the possible artifacts induced by specimen preparation when examining amorphous alloys under TEM.
文摘A porous anodic alumina (PAA) film has been investigated to realise highly-ordered nano-porous structures. A two-step anodization process is used to anodize aluminium into size-controllable aluminium oxide. In this paper, we investigate how anodization parameters affect nano-porous structures, such as voltage and time of pretreatment, anodization voltage and time, pore widening time. The results showed pretreatment is important to obtain a smooth surface for anodizing. The pore size is controllable between 30 and 80 nm, with a linear fit curve. The interpore size is constant at around 95 nm, and the pore densities are between 1010 and 1011 cm–2. The formation of straight vertical walls is crucial if the PAA film is to be subsequently used as the template for the growth of metal nanowire arrays.
