Friction stir welding was used to join two AA2060-T8 plates,and then the effect of precipitate evolution on microstructure and corrosion behavior of the joint was investigated.The evolution of precipitates on the top ...Friction stir welding was used to join two AA2060-T8 plates,and then the effect of precipitate evolution on microstructure and corrosion behavior of the joint was investigated.The evolution of precipitates on the top surface of the joint was characterized by scanning electron microscopy and transmission electron microscopy.The corrosion behaviors of different regions in the joint were investigated by an electrochemistry method and an alternating salt spray exposure.The corrosion was mainly dependent on the nature of precipitates in each region of the joint.The shoulder affected zone had the worst corrosion resistance as a result of the re-dissolved ofθ′(Al2Cu),T1(Al2CuLi)andδ′(Al3Li)phases,the formation of intergranular precipitates and precipitate-free zones.However,the thermomechanically affected zone had a slightly improved corrosion resistance because it had no intergranular precipitates.The heat affected zone and base metal had the best corrosion resistance.展开更多
Duplex stainless steels(DSSs)are suffering from various localized corrosion attacks such as pitting,selective dissolution,crevice corrosion during their service period.It is of great value to quantitatively analyze an...Duplex stainless steels(DSSs)are suffering from various localized corrosion attacks such as pitting,selective dissolution,crevice corrosion during their service period.It is of great value to quantitatively analyze and grasp the micro-electrochemical corrosion behavior and related mechanism for DSSs on the micrometer or even smaller scales.In this work,scanning Kelvin probe force microscopy(SKPFM)and energy dispersive spectroscopy(EDS)measurements were performed to reveal the difference between the austenite phase and ferrite phase in microregion of DSS 2205.Then traditional electrochemical impedance spectroscopy(EIS)and potentiodynamic polarization(PDP)tests were employed for micro-electrochemical characterization of DSS 2205 with different proportion phases inϕ40 andϕ10μm micro holes.Both of them can only be utilized for qualitative or semi-quantitative micro-electrochemical characterization of DSS 2205.Coulostatic perturbation method was employed for quantitative micro-electrochemical characterization of DSS 2205.What is more,the applicable conditions of coulostatic perturbation were analyzed in depth by establishing a detailed electrochemical interface circuit.A series of microregion coulostatic perturbations for DSS 2205 with different proportion phases inϕ10μm micro holes showed that as the austenite proportion increases,the corresponding polarization resistance of microregion increases linearly.展开更多
This work demonstrates the viability of the powder-mixed micro-electrochemical discharge machining(PMECDM) process to fabricate micro-holes on C103 niobium-based alloy for high temperature applications.Three processes...This work demonstrates the viability of the powder-mixed micro-electrochemical discharge machining(PMECDM) process to fabricate micro-holes on C103 niobium-based alloy for high temperature applications.Three processes are involved simultaneously i.e.spark erosion,chemical etching,and abrasive grinding for removal of material while the classical electrochemical discharge machining process involves double actions i.e.spark erosion,and chemical etching.The powder-mixed electrolyte process resulted in rapid material removal along with a better surface finish as compared to the classical microelectrochemical discharge machining(MECDM).Further,the results are optimized through a multiobjective optimization approach and study of the surface topography of the hole wall surface obtained at optimized parameters.In the selected range of experimental parameters,PMECDM shows a higher material removal rate(MRR) and lower surface roughness(R_(a))(MRR:2.8 mg/min and R_(a) of 0.61 μm) as compared to the MECDM process(MRR:2.01 mg/min and corresponding Raof 1.11 μm).A detailed analysis of the results is presented in this paper.展开更多
基金Beijing Natural Science Foundation (Grant No. 3194048)China Friction Stir Welding Center and to Beijing Key Laboratory of Pipeline Critical Technology and Equipment for Deepwater Oil & Gas Development (Grant No. BIPT2018006) for the financial support
文摘Friction stir welding was used to join two AA2060-T8 plates,and then the effect of precipitate evolution on microstructure and corrosion behavior of the joint was investigated.The evolution of precipitates on the top surface of the joint was characterized by scanning electron microscopy and transmission electron microscopy.The corrosion behaviors of different regions in the joint were investigated by an electrochemistry method and an alternating salt spray exposure.The corrosion was mainly dependent on the nature of precipitates in each region of the joint.The shoulder affected zone had the worst corrosion resistance as a result of the re-dissolved ofθ′(Al2Cu),T1(Al2CuLi)andδ′(Al3Li)phases,the formation of intergranular precipitates and precipitate-free zones.However,the thermomechanically affected zone had a slightly improved corrosion resistance because it had no intergranular precipitates.The heat affected zone and base metal had the best corrosion resistance.
基金financial support from the Ministry of Science and Technology, China for the national key research and development plan (No. 2017YFB0701904)China Nuclear Power Engineering Co., Ltd. (No. KY1672)the 111 Project (No. B12012)
文摘Duplex stainless steels(DSSs)are suffering from various localized corrosion attacks such as pitting,selective dissolution,crevice corrosion during their service period.It is of great value to quantitatively analyze and grasp the micro-electrochemical corrosion behavior and related mechanism for DSSs on the micrometer or even smaller scales.In this work,scanning Kelvin probe force microscopy(SKPFM)and energy dispersive spectroscopy(EDS)measurements were performed to reveal the difference between the austenite phase and ferrite phase in microregion of DSS 2205.Then traditional electrochemical impedance spectroscopy(EIS)and potentiodynamic polarization(PDP)tests were employed for micro-electrochemical characterization of DSS 2205 with different proportion phases inϕ40 andϕ10μm micro holes.Both of them can only be utilized for qualitative or semi-quantitative micro-electrochemical characterization of DSS 2205.Coulostatic perturbation method was employed for quantitative micro-electrochemical characterization of DSS 2205.What is more,the applicable conditions of coulostatic perturbation were analyzed in depth by establishing a detailed electrochemical interface circuit.A series of microregion coulostatic perturbations for DSS 2205 with different proportion phases inϕ10μm micro holes showed that as the austenite proportion increases,the corresponding polarization resistance of microregion increases linearly.
文摘This work demonstrates the viability of the powder-mixed micro-electrochemical discharge machining(PMECDM) process to fabricate micro-holes on C103 niobium-based alloy for high temperature applications.Three processes are involved simultaneously i.e.spark erosion,chemical etching,and abrasive grinding for removal of material while the classical electrochemical discharge machining process involves double actions i.e.spark erosion,and chemical etching.The powder-mixed electrolyte process resulted in rapid material removal along with a better surface finish as compared to the classical microelectrochemical discharge machining(MECDM).Further,the results are optimized through a multiobjective optimization approach and study of the surface topography of the hole wall surface obtained at optimized parameters.In the selected range of experimental parameters,PMECDM shows a higher material removal rate(MRR) and lower surface roughness(R_(a))(MRR:2.8 mg/min and R_(a) of 0.61 μm) as compared to the MECDM process(MRR:2.01 mg/min and corresponding Raof 1.11 μm).A detailed analysis of the results is presented in this paper.
