It is of great significance to study the corrosion process of aluminum(Al)alloys fasteners in order to mitigate corrosion for their widespread applications.In this paper,a method for enhancing the corrosion resistance...It is of great significance to study the corrosion process of aluminum(Al)alloys fasteners in order to mitigate corrosion for their widespread applications.In this paper,a method for enhancing the corrosion resistance of Al alloy fasteners is proposed.7075 Al alloy parts with a fine-grained microstructure were prepared by pre-heat treatment(PHT),combined subsequent equal channel angular pressing(ECAP)and cold upsetting(CU).The corrosion behavior of the specimens was investigated by intergranular corrosion and electrochemical test.Microstructure investigations were carried out by field emission scanning electron microscopy,energy dispersive spectrometer and transmission electron microscopy.The relationship between microstructural evolution and corrosion resistance changes was also explored.The results show that both PHT and ECAP-CU significantly improved the corrosion resistance of the samples and modified the corrosion process.The open circuit potential,corrosion current density and corrosion rate of the alloy on electrochemical test were(-0.812±8.854)×10^(-5) V(vs.SCE),(6.379±0.025)×10^(-6) A/cm^(2) and 0.066 mm/year,respectively,and the intergranular corrosion depth was(557±8)μm.The main factor controlling the corrosion behavior was the microstructure evolution.After PHT,the disappearance of the dendritic structure and the dissolution of the nonequilibrium second phase eliminated the potential difference between the phases,reducing the free energy in the as cast state.When ECAP-CU was used after PHT,the grain refinement was accompanied by a high density of grain boundaries and dislocations,which led to the formation of a denser passivation film on the alloy surface,improving the corrosion resistance in an aggressive environment.展开更多
In this study,the interaction between deformation and precipitates during multiple equal channel angular pressing(ECAP)deformations and inter-pass aging combination and its effect on the mechanical properties of 7050 ...In this study,the interaction between deformation and precipitates during multiple equal channel angular pressing(ECAP)deformations and inter-pass aging combination and its effect on the mechanical properties of 7050 aluminum alloy are studied.The result show that ECAP induces numerous substructures and dislocations,effectively promoting the precipitation of theηʹphase exhibiting a bimodal structure during inter-pass aging.Following inter-pass aging and subsequent ECAP,the decrease in grain size(4.8μm)is together with the increase in dislocation density(1.24×10^(15) m^(−2))due to the pinning effect of the precipitated phase.Simultaneously,the dislocation motion causes the second phase particles to become even finer and more diffuse.The synergistic effects of precipitation strengthening,fine grain strengthening,and dislocation strengthening collectively enhance the high strength of aluminum alloys,with ultimate tensile strength and yield strength reaching approximately 610 and 565 MPa,respectively.Meanwhile,ductility remains largely unchanged,primarily due to coordinated grain boundary sliding and the uniform and fine dispersion of second phase particles.展开更多
基金Project(52275350)supported by the National Natural Science Foundation of ChinaProject(0301006)supported by International Cooperative Scientific Research Platform of SUES,China。
文摘It is of great significance to study the corrosion process of aluminum(Al)alloys fasteners in order to mitigate corrosion for their widespread applications.In this paper,a method for enhancing the corrosion resistance of Al alloy fasteners is proposed.7075 Al alloy parts with a fine-grained microstructure were prepared by pre-heat treatment(PHT),combined subsequent equal channel angular pressing(ECAP)and cold upsetting(CU).The corrosion behavior of the specimens was investigated by intergranular corrosion and electrochemical test.Microstructure investigations were carried out by field emission scanning electron microscopy,energy dispersive spectrometer and transmission electron microscopy.The relationship between microstructural evolution and corrosion resistance changes was also explored.The results show that both PHT and ECAP-CU significantly improved the corrosion resistance of the samples and modified the corrosion process.The open circuit potential,corrosion current density and corrosion rate of the alloy on electrochemical test were(-0.812±8.854)×10^(-5) V(vs.SCE),(6.379±0.025)×10^(-6) A/cm^(2) and 0.066 mm/year,respectively,and the intergranular corrosion depth was(557±8)μm.The main factor controlling the corrosion behavior was the microstructure evolution.After PHT,the disappearance of the dendritic structure and the dissolution of the nonequilibrium second phase eliminated the potential difference between the phases,reducing the free energy in the as cast state.When ECAP-CU was used after PHT,the grain refinement was accompanied by a high density of grain boundaries and dislocations,which led to the formation of a denser passivation film on the alloy surface,improving the corrosion resistance in an aggressive environment.
基金Project(52275350)supported by the National Natural Science Foundation of ChinaProject(0301006)supported by the International Cooperative Scientific Research Platform of SUES,China。
文摘In this study,the interaction between deformation and precipitates during multiple equal channel angular pressing(ECAP)deformations and inter-pass aging combination and its effect on the mechanical properties of 7050 aluminum alloy are studied.The result show that ECAP induces numerous substructures and dislocations,effectively promoting the precipitation of theηʹphase exhibiting a bimodal structure during inter-pass aging.Following inter-pass aging and subsequent ECAP,the decrease in grain size(4.8μm)is together with the increase in dislocation density(1.24×10^(15) m^(−2))due to the pinning effect of the precipitated phase.Simultaneously,the dislocation motion causes the second phase particles to become even finer and more diffuse.The synergistic effects of precipitation strengthening,fine grain strengthening,and dislocation strengthening collectively enhance the high strength of aluminum alloys,with ultimate tensile strength and yield strength reaching approximately 610 and 565 MPa,respectively.Meanwhile,ductility remains largely unchanged,primarily due to coordinated grain boundary sliding and the uniform and fine dispersion of second phase particles.
基金Project(52275350)supported by the National Natural Science Foundation of ChinaProject(0301006)supported by International Cooperative Scientific Research Platform of SUES,China。
