Plasma electrolytic oxidation (PEO) ceramic coatings were fabricated in a silicate-based electrolyte with the addition of potassium fluorozirconate (K2ZrF6) on 6063 aluminum alloy, and the effects of current density o...Plasma electrolytic oxidation (PEO) ceramic coatings were fabricated in a silicate-based electrolyte with the addition of potassium fluorozirconate (K2ZrF6) on 6063 aluminum alloy, and the effects of current density on microstructure and properties of the PEO coatings were studied. It was found that pore density of the coatings decreased with increasing the current density. The tribological and hardness tests suggested that the ceramic coating produced under the current density of 15 A/dm2showed the best mechanical property, which matched well with the phase analysis. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves proved that the coating obtained under 15 A/dm2 displayed the best anti-corrosion property, which was directly connected with morphologies of coatings.展开更多
The microstructure and mechanical properties of ceramic coatings formed on 6063 aluminium alloy obtained in silicate-,borate- and aluminate-based electrolyte without and with nanoadditive Al2O3 and TiO2 by micro-arc o...The microstructure and mechanical properties of ceramic coatings formed on 6063 aluminium alloy obtained in silicate-,borate- and aluminate-based electrolyte without and with nanoadditive Al2O3 and TiO2 by micro-arc oxidation（MAO） were studied by scanning electron microscopy（SEM）,energy-dispersive X-ray spectroscopy（EDS）,X-ray diffraction（XRD）,microhardness and friction-abrasion tests,respectively.SEM results show that coatings with nanoadditive have less porosities than those without nanoadditive.XRD results reveal that nanoadditive-containing coatings contain more oxides compared with nanoadditive-free coatings in all cases,which are consistent with the EDS analysis.Mechanical properties tests show that nanoadditive Al2O3-containing coatings have higher microhardness values compared with the other coatings obtained in silicate-,borate- and aluminate-based electrolyte.On the other hand,nanoadditive has a positive effect on improving the wearing-resistance of MAO coatings in all cases.Furthermore,the borate-MAO coatings present an inferior anti-wearing property compared with the silicate- and aluminate-MAO coatings for both the nanoadditive-free and nanoadditive-containing coatings.展开更多
In this work, a comparison study on corrosion behavior of extruded near eutectic Al-12.3%Si-0.26%Mg and 6063 alloys has been carried out by mass loss test in 4% H2SO4 aqueous solution in the open air and potentiodynam...In this work, a comparison study on corrosion behavior of extruded near eutectic Al-12.3%Si-0.26%Mg and 6063 alloys has been carried out by mass loss test in 4% H2SO4 aqueous solution in the open air and potentiodynamic polarization test in 3.5 wt.% NaCI aqueous solution. Results indicate that the corrosion resistance of the near eutectic AI-Si-Mg alloy is less than that of 6063 alloy. Macro/microscopy and scanning electron microscopy results clearly show the difference of the corrosion progress of these two alloys in 4% H2SO4 aqueous solution. The corrosion type of 6063 alloy is pitting corrosion. The Mg2Si and AIFeSi particles and surface defects act as nucleation sites for pitting, and the amount and distribution of them have a significant effect on the pitting behavior. For the near eutectic alloy, there are two types of corrosion cells. One is between the extruded primary α-AI and the eutectic, the other is between the eutectic AI and eutectic Si particles. Combination of these two types of corrosion cells leads to a lower corrosion resistance, a higher mass loss of the near eutectic alloy compared with 6063 alloy, and the formation of the paralleling corroded grooves.展开更多
During continuous extrusion,the welds were formed at the confluence of two billets.Influences of extrusion wheel rotational speed on micromorphology and properties of welds of 6063 Al alloy were investigated through m...During continuous extrusion,the welds were formed at the confluence of two billets.Influences of extrusion wheel rotational speed on micromorphology and properties of welds of 6063 Al alloy were investigated through microstructure observation,tensile test,and SEM analyses.Welding parameters were analyzed using finite element simulation.Results indicated that metal welding was remarkably affected by oxide on outer surface of the double billets during continuous extrusion.Degree of oxide breakage on the welding surface increased due to the evident increase in effective strain rate with increasing extrusion speed.The high temperature induced by increased extrusion speed accelerated the formation of metallurgical bonding.A portion of weld seam lines slowly disappeared,and the proportion of the welding interface that failed to reach metallurgical bonding was also gradually reduced.Tensile strength and elongation of the weld specimen increased with the increase of extrusion speed.展开更多
In order to develop the appropriate constitutive equation which can precisely model high temperature flow stress of 6063 Al alloy, a series of isothermal hot compression tests were performed at temperatures from 573 t...In order to develop the appropriate constitutive equation which can precisely model high temperature flow stress of 6063 Al alloy, a series of isothermal hot compression tests were performed at temperatures from 573 to 773 K and strain rates from 0.5 to 50 s?1 on a Gleeble?1500 thermo-simulation machine. Zener–Hollomon parameter in an exponent-type equation was used to describe the combined effects of temperature and strain rate on hot deformation behaviour of 6063 Al alloy, whereas the influence of strain was incorporated in the developed constitutive equation by considering material constants (α,n,Q andA) to be 4th order polynomial functions of strain. The results show that the developed constitutive equation can accurately predict high temperature flow stress of 6063 Al alloy, which demonstrates that it can be suitable for simulating hot deformation processes such as extrusion and forging, and for properly designing the deformation parameters in engineering practice.展开更多
Bending deformation behaviors of solution treated(ST),natural aged(NA)and T6tempered6063aluminum alloy sheetswere studied by three-point bending tests.The changes of bending force,interior angle,bending radius and she...Bending deformation behaviors of solution treated(ST),natural aged(NA)and T6tempered6063aluminum alloy sheetswere studied by three-point bending tests.The changes of bending force,interior angle,bending radius and sheet thickness in thefillet region were analyzed by experimental measurements and numerical simulations.The results showed that the bendingcharacteristics were strongly dependent on the heat treatment conditions.The T6alloy sheets were bent more sharply and localplastic deformation occurred severely in the fillet region.However,the ST and NA alloy sheets exhibited relatively uniform bendingdeformation and large bending radius.The bending force of T6alloy was the highest,followed by the NA alloy and that of the STalloy was minimum.After unloading,as compared with the ST and NA alloys,the springback of T6alloys was markedly larger.Theaging time showed a positive sensitivity on the springback and non-uniform bending deformability.The bending characteristics areattributed to the combined effects of yield strength,yield ratio and coefficient of neutral layer.展开更多
The quench sensitivity of 6063 alloy was investigated via constructing time-temperature-property（TTP） curves by interrupted quenching technique and transmission electron microscopy（TEM） analysis.The results show t...The quench sensitivity of 6063 alloy was investigated via constructing time-temperature-property（TTP） curves by interrupted quenching technique and transmission electron microscopy（TEM） analysis.The results show that the quench sensitivity of 6063 alloy is lower than that of 6061 or 6082 alloy,and the critical temperature ranges from 300 to 410℃ with the nose temperature of about 360℃.From TEM analysis,heterogeneous precipitate β-Mg2Si is prior to nucleate on the（AlxFeySiz） dispersoids in the critical temperature range,and grows up most rapidly at the nose temperature of 360℃.The heterogeneous precipitation leads to a low concentration of solute,which consequently reduces the amount of the strengthening phase β＇＇ after aging.In the large-scale industrial production of 6063 alloy,the cooling rate during quenching should be enhanced as high as possible in the quenching sensitive temperature range（410-300℃） to suppress the heterogeneous precipitation to get optimal mechanical properties,and it should be slowed down properly from the solution temperature to 410℃ and below 300℃ to reduce the residual stress.展开更多
The effect of dynamic recrystallization(DRX)on the microstructure and mechanical properties of 6063 aluminum alloy profile during porthole die extrusion was studied through experiment and simulation.The grain morpholo...The effect of dynamic recrystallization(DRX)on the microstructure and mechanical properties of 6063 aluminum alloy profile during porthole die extrusion was studied through experiment and simulation.The grain morphology was observed by means of electron backscatter diffraction(EBSD)technology.The results show that,at low ram speeds,increasing the ram speed caused an increase in DRX fraction due to the increase of temperature and strain rate.In contrast,at high ram speeds,further increasing ram speed had much less effect on the temperature,and the DRX faction decreased due to high stain rates.The microhardness and fraction of low angle boundaries in the welding zones were lower than those in the matrix zones.The grain size in the welding zone was smaller than that in the matrix zone due to lower DRX fraction.The decrease of grain size and increase of extrudate temperature were beneficial to the improvement of microhardness.展开更多
The influence of alumina volume percent and solution heat-treatment on the corrosion behaviour of Al (6063) composites and its monolithic alloy in salt water, basic and acidic environments is investigated. Al (6063) ...The influence of alumina volume percent and solution heat-treatment on the corrosion behaviour of Al (6063) composites and its monolithic alloy in salt water, basic and acidic environments is investigated. Al (6063) – Al2O3 particulate composites containing 6, 9, 15, and 18 volume percent alumina were produced by adopting two step stir casting. Mass loss and corrosion rate measurements were utilized as criteria for evaluating the corrosion behaviour of the composites. It is observed that Al (6063) – Al2O3 composites exhibited excellent corrosion resistance in NaCl medium than in the NaOH and H2SO4 media. The unreinforced alloy exhibited slightly superior corrosion resistance than the composites in NaCl and NaOH media but the composites had better corrosion resistance in H2SO4 medium. Furthermore, solution heat-treatment resulted in improved corrosion resistance for both the composites and the unreinforced alloy while the effect of volume percent alumina on corrosion resistance did not follow a consistent trend.展开更多
Severe surface roughening during plastic deforming of aluminum alloy parts can produce ＂orange peel＂ defects. To analyze ＂orange peel＂ of 6063 aluminum alloy tube quantificationally, the tensile tests of trapezoid...Severe surface roughening during plastic deforming of aluminum alloy parts can produce ＂orange peel＂ defects. To analyze ＂orange peel＂ of 6063 aluminum alloy tube quantificationally, the tensile tests of trapezoidal specimens were carried out. The tubes with different grain sizes were obtained by spinning and subsequent annealing heat treatment. The macroscopical behavior of surface roughening was characterized by surface roughness Ra using a laser scanning confocal microscope. The corresponding microscopic behavior was reflected by microstructures of specimens and in-situ observation using electron back-scattered diffraction（EBSD）. The obtained results show that the surface roughness increased firstly with increasing strain and then decreased slightly. There was a critical strain for aluminum alloy tube, below which ＂orange peel＂ defect would not occur. For the tube with a mean grain size of 80, 105, 130 and 175 μm, the critical strains were 10.17%, 5.74%, 3.15% and 1.62%, respectively. Meanwhile, the surface roughening behavior was produced by serious inhomogeneous deformation between grains as strain increased, and was aggravated as the grain size increased due to the larger local deformation in larger grains.展开更多
To study the damage and fracture mechanism of 6063 aluminum alloy under different stress states,three kinds of representative triaxial stress states have been adopted,namely smooth tensile,notch tensile,and pure shear...To study the damage and fracture mechanism of 6063 aluminum alloy under different stress states,three kinds of representative triaxial stress states have been adopted,namely smooth tensile,notch tensile,and pure shear.The results of the study indicate the following.During the notch tensile test,a relatively higher stress triaxiality appears in the root of the notch.With the applied loading increasing,the volume fraction of microvoids in the root of the notch increases continuously.When it reaches the critical volume fraction of microvoids,the specimen fractures.During the pure shear test,the stress triaxiality almost equals to zero,and there is almost no microvoids but a shear band at the center of the butterfly specimen.The shear band results from nonuniform deformation constantly under the shear stress.With stress concentration,cracks are produced within the shear band and are later coalesced.When the equivalent plastic strain reaches the critical value（equivalent plastic fracture strain）,the butterfly specimen fractures.During the smooth tensile test,the stress triaxiality in the gauge of the specimen remains constant at 0.33.Thus,the volume of microvoids of the smooth tensile test is less than that of the notch tensile test and the smooth specimen fractures due to shearing between microvoids.The G-T-N damage model and Johnson-Cook model are used to simulate the notch tensile and shear test,respectively.The simulated engineering stress-strain curves fit the measured engineering stress-strain curves very well.In addition,the empirical damage evolution equation for the notch specimen is obtained from the experimental data and FEM simulations.展开更多
The hot compression test of 6063 Al alloy was performed on a Gleeble-1500 thermo-simulation machine, and the forming of 6063 rod cxtrudate in low-temperature high-speed extrusion was simulated with extrusion ratio of ...The hot compression test of 6063 Al alloy was performed on a Gleeble-1500 thermo-simulation machine, and the forming of 6063 rod cxtrudate in low-temperature high-speed extrusion was simulated with extrusion ratio of 25 on the platform of DEFORM 2D successfully. From the compression experimental results, the flow stress model of this Al alloy is obtained which could be the constitutive equation in the simulation of low-temperature high-speed extrusion process. From the numerical simulation results, there is a higher strain concentration at the entrance of the die and the exit temperature reaches up to 522 ℃ in low-temperature high-speed extrusion, which approaches to the quenching temperature of the 6063 Al alloy. The results show that the low-temperature high-speed extrusion method as a promsing one can reduce energy consumption effectively.展开更多
The deformation behavior characteristics of 6063 aluminum alloy were studied experimentally by isothermal compression tests on a Gleeble- 1500 thermal-mechanical simulator. Cylindrical specimens of 14mm in height and ...The deformation behavior characteristics of 6063 aluminum alloy were studied experimentally by isothermal compression tests on a Gleeble- 1500 thermal-mechanical simulator. Cylindrical specimens of 14mm in height and 10mm in diameter were compressed dynamically at temperatures ranging from 473 to 723K and at higher strain rntes from 5 to 30s^-1. It is fouud that the flow curves not only depend on the strain rate and temperature but nlso on the dynamic recovery aud recrystallization behavior. The results show that the flow stress decreased with the increase of temperature, while increased with the increase of strain rate. The discontinuous dynamic recrystallization （DDRX） may take place at a high strain rate of 20s^-1 under the tested conditions. At 30s^-1 , the flow curve can exhibit,flow softening due to the effect of temperature rise that raised the temperature by aboat 32K in less than 0.05s.展开更多
A two-step ultrasonic-assisted brazing method and its associated apparatus were developed to make 6063 aluminum alloys joints with Al-Si-Mg filler metal. The burst phenomenon and the effect of ultrasonic direction and...A two-step ultrasonic-assisted brazing method and its associated apparatus were developed to make 6063 aluminum alloys joints with Al-Si-Mg filler metal. The burst phenomenon and the effect of ultrasonic direction and time, as well as the welding joint geometry on the burst phenomenon were investigated. The results show that the burst phenomenon occurs in the liquid filler metal under the effects of high current density, heat, and interaction force. The burst phenomenon is eliminated when the oxide film on the edge of the cross-section of the two parent metals is removed with more than or equal to 6 s ultrasonic time. A model of formation and elimination for burst was proposed, through which the blasting phenomenon can be controlled by changing the ultrasonic time and the geometrical shape of the welded joint.展开更多
Plasma electrolytic oxidation(PEO) coatings were fabricated on 6063 aluminum alloy in a cheap and convenient electrolyte. The effect of different current densities, i e, 5, 10, 15, and 20 A/dm2on the microstructure an...Plasma electrolytic oxidation(PEO) coatings were fabricated on 6063 aluminum alloy in a cheap and convenient electrolyte. The effect of different current densities, i e, 5, 10, 15, and 20 A/dm2on the microstructure and corrosion behavior of coatings was comprehensively studied by scanning electron microscopy(SEM), stereoscopic microscopy, potentiodynamic polarization and electrochemical impedance spectroscopy(EIS), respectively. It is found that the pore density decreases and the pore size increases with increasing current density. The XRD results show that the coatings are only composed of α-Al2O3and γ-Al2O3. Potentiodynamic polarization test proves that the coating formed under 10 A/dm2possesses the best anticorrosion property. The long time EIS test shows that the coating under 10 A/dm2is able to protect the aluminum alloy substrate after long time of immersion in 0.59 M NaCl solution, which confirms the salt solution immersion test results in 2 M NaCl solution.展开更多
The present article reports on characterization studies performed on amorphized nanostructured Al 6063 alloy powder synthesized by mechanical alloying (MA). The as-milled powder was characterized by X-ray diffraction ...The present article reports on characterization studies performed on amorphized nanostructured Al 6063 alloy powder synthesized by mechanical alloying (MA). The as-milled powder was characterized by X-ray diffraction (XRD) for investigating the development of crystallite nature and determining the different phases of the materials present, scanning electron microscope (SEM) was used for in depth morphological study and High Resolution-transmission electron microscope (HR-TEM) was employed to ensure the development of a nano-structured nature of the Al 6063 matrix. In the present work alloyed powder was milled for 20 h and 40 h at 300 rpm;and 20 h at 700 rpm in a hardened stainless steel medium. Using Williamson-Hall equation;crystallite size, lattice strain and lattice parameter of Al 6063 nanostructure alloy powder was estimated with broadening of XRD peaks. XRD results showed that the crystallite size of Al 6063 alloy powder reached 32 and 53 nm after 20 h at 700 rpm and 40 h at 300 rpm respectively.展开更多
基金Project(51371039)supported by the National Natural Science Foundation of China
文摘Plasma electrolytic oxidation (PEO) ceramic coatings were fabricated in a silicate-based electrolyte with the addition of potassium fluorozirconate (K2ZrF6) on 6063 aluminum alloy, and the effects of current density on microstructure and properties of the PEO coatings were studied. It was found that pore density of the coatings decreased with increasing the current density. The tribological and hardness tests suggested that the ceramic coating produced under the current density of 15 A/dm2showed the best mechanical property, which matched well with the phase analysis. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves proved that the coating obtained under 15 A/dm2 displayed the best anti-corrosion property, which was directly connected with morphologies of coatings.
基金Project(51371039)supported by the National Natural Science Foundation of China
文摘The microstructure and mechanical properties of ceramic coatings formed on 6063 aluminium alloy obtained in silicate-,borate- and aluminate-based electrolyte without and with nanoadditive Al2O3 and TiO2 by micro-arc oxidation（MAO） were studied by scanning electron microscopy（SEM）,energy-dispersive X-ray spectroscopy（EDS）,X-ray diffraction（XRD）,microhardness and friction-abrasion tests,respectively.SEM results show that coatings with nanoadditive have less porosities than those without nanoadditive.XRD results reveal that nanoadditive-containing coatings contain more oxides compared with nanoadditive-free coatings in all cases,which are consistent with the EDS analysis.Mechanical properties tests show that nanoadditive Al2O3-containing coatings have higher microhardness values compared with the other coatings obtained in silicate-,borate- and aluminate-based electrolyte.On the other hand,nanoadditive has a positive effect on improving the wearing-resistance of MAO coatings in all cases.Furthermore,the borate-MAO coatings present an inferior anti-wearing property compared with the silicate- and aluminate-MAO coatings for both the nanoadditive-free and nanoadditive-containing coatings.
基金supported by Jiangsu Graduated-student Innovation Program of China(No.CXZZ-0146)the Scientific Research Foundation of Graduate School of Southeast University
文摘In this work, a comparison study on corrosion behavior of extruded near eutectic Al-12.3%Si-0.26%Mg and 6063 alloys has been carried out by mass loss test in 4% H2SO4 aqueous solution in the open air and potentiodynamic polarization test in 3.5 wt.% NaCI aqueous solution. Results indicate that the corrosion resistance of the near eutectic AI-Si-Mg alloy is less than that of 6063 alloy. Macro/microscopy and scanning electron microscopy results clearly show the difference of the corrosion progress of these two alloys in 4% H2SO4 aqueous solution. The corrosion type of 6063 alloy is pitting corrosion. The Mg2Si and AIFeSi particles and surface defects act as nucleation sites for pitting, and the amount and distribution of them have a significant effect on the pitting behavior. For the near eutectic alloy, there are two types of corrosion cells. One is between the extruded primary α-AI and the eutectic, the other is between the eutectic AI and eutectic Si particles. Combination of these two types of corrosion cells leads to a lower corrosion resistance, a higher mass loss of the near eutectic alloy compared with 6063 alloy, and the formation of the paralleling corroded grooves.
基金financial supports from the National Natural Science Foundation of China(Nos.51705062,51675074)the Department of Education Fund Item of Liaoning Province,China(No.JDL 2019021)。
文摘During continuous extrusion,the welds were formed at the confluence of two billets.Influences of extrusion wheel rotational speed on micromorphology and properties of welds of 6063 Al alloy were investigated through microstructure observation,tensile test,and SEM analyses.Welding parameters were analyzed using finite element simulation.Results indicated that metal welding was remarkably affected by oxide on outer surface of the double billets during continuous extrusion.Degree of oxide breakage on the welding surface increased due to the evident increase in effective strain rate with increasing extrusion speed.The high temperature induced by increased extrusion speed accelerated the formation of metallurgical bonding.A portion of weld seam lines slowly disappeared,and the proportion of the welding interface that failed to reach metallurgical bonding was also gradually reduced.Tensile strength and elongation of the weld specimen increased with the increase of extrusion speed.
基金Project(2012B090600051)supported by Al and Mg Light Alloys Platform on the Unity of Industry,Education and Research Innovation of Guangdong Province,ChinaProject(2012B001)supported by the Ph D Start-up Fund of Guangzhou Research Institute of Non-ferrous Metals,China
文摘In order to develop the appropriate constitutive equation which can precisely model high temperature flow stress of 6063 Al alloy, a series of isothermal hot compression tests were performed at temperatures from 573 to 773 K and strain rates from 0.5 to 50 s?1 on a Gleeble?1500 thermo-simulation machine. Zener–Hollomon parameter in an exponent-type equation was used to describe the combined effects of temperature and strain rate on hot deformation behaviour of 6063 Al alloy, whereas the influence of strain was incorporated in the developed constitutive equation by considering material constants (α,n,Q andA) to be 4th order polynomial functions of strain. The results show that the developed constitutive equation can accurately predict high temperature flow stress of 6063 Al alloy, which demonstrates that it can be suitable for simulating hot deformation processes such as extrusion and forging, and for properly designing the deformation parameters in engineering practice.
基金Projects(U1664252,51605234)supported by the National Natural Science Foundation of ChinaProject(2016YFB0101700)supported by the National Key Research and Development Program of ChinaProject(31665004)supported by the Open Fund of State Key Laboratory of Advanced Design and Manufacture for Vehicle Body
文摘Bending deformation behaviors of solution treated(ST),natural aged(NA)and T6tempered6063aluminum alloy sheetswere studied by three-point bending tests.The changes of bending force,interior angle,bending radius and sheet thickness in thefillet region were analyzed by experimental measurements and numerical simulations.The results showed that the bendingcharacteristics were strongly dependent on the heat treatment conditions.The T6alloy sheets were bent more sharply and localplastic deformation occurred severely in the fillet region.However,the ST and NA alloy sheets exhibited relatively uniform bendingdeformation and large bending radius.The bending force of T6alloy was the highest,followed by the NA alloy and that of the STalloy was minimum.After unloading,as compared with the ST and NA alloys,the springback of T6alloys was markedly larger.Theaging time showed a positive sensitivity on the springback and non-uniform bending deformability.The bending characteristics areattributed to the combined effects of yield strength,yield ratio and coefficient of neutral layer.
文摘The quench sensitivity of 6063 alloy was investigated via constructing time-temperature-property（TTP） curves by interrupted quenching technique and transmission electron microscopy（TEM） analysis.The results show that the quench sensitivity of 6063 alloy is lower than that of 6061 or 6082 alloy,and the critical temperature ranges from 300 to 410℃ with the nose temperature of about 360℃.From TEM analysis,heterogeneous precipitate β-Mg2Si is prior to nucleate on the（AlxFeySiz） dispersoids in the critical temperature range,and grows up most rapidly at the nose temperature of 360℃.The heterogeneous precipitation leads to a low concentration of solute,which consequently reduces the amount of the strengthening phase β＇＇ after aging.In the large-scale industrial production of 6063 alloy,the cooling rate during quenching should be enhanced as high as possible in the quenching sensitive temperature range（410-300℃） to suppress the heterogeneous precipitation to get optimal mechanical properties,and it should be slowed down properly from the solution temperature to 410℃ and below 300℃ to reduce the residual stress.
基金Project(U1664252)supported by the National Natural Science Foundation of China
文摘The effect of dynamic recrystallization(DRX)on the microstructure and mechanical properties of 6063 aluminum alloy profile during porthole die extrusion was studied through experiment and simulation.The grain morphology was observed by means of electron backscatter diffraction(EBSD)technology.The results show that,at low ram speeds,increasing the ram speed caused an increase in DRX fraction due to the increase of temperature and strain rate.In contrast,at high ram speeds,further increasing ram speed had much less effect on the temperature,and the DRX faction decreased due to high stain rates.The microhardness and fraction of low angle boundaries in the welding zones were lower than those in the matrix zones.The grain size in the welding zone was smaller than that in the matrix zone due to lower DRX fraction.The decrease of grain size and increase of extrudate temperature were beneficial to the improvement of microhardness.
文摘The influence of alumina volume percent and solution heat-treatment on the corrosion behaviour of Al (6063) composites and its monolithic alloy in salt water, basic and acidic environments is investigated. Al (6063) – Al2O3 particulate composites containing 6, 9, 15, and 18 volume percent alumina were produced by adopting two step stir casting. Mass loss and corrosion rate measurements were utilized as criteria for evaluating the corrosion behaviour of the composites. It is observed that Al (6063) – Al2O3 composites exhibited excellent corrosion resistance in NaCl medium than in the NaOH and H2SO4 media. The unreinforced alloy exhibited slightly superior corrosion resistance than the composites in NaCl and NaOH media but the composites had better corrosion resistance in H2SO4 medium. Furthermore, solution heat-treatment resulted in improved corrosion resistance for both the composites and the unreinforced alloy while the effect of volume percent alumina on corrosion resistance did not follow a consistent trend.
基金Project(IRT1229)supported by Program for Chang-jiang Scholars and Innovative Research Team in University,China
文摘Severe surface roughening during plastic deforming of aluminum alloy parts can produce ＂orange peel＂ defects. To analyze ＂orange peel＂ of 6063 aluminum alloy tube quantificationally, the tensile tests of trapezoidal specimens were carried out. The tubes with different grain sizes were obtained by spinning and subsequent annealing heat treatment. The macroscopical behavior of surface roughening was characterized by surface roughness Ra using a laser scanning confocal microscope. The corresponding microscopic behavior was reflected by microstructures of specimens and in-situ observation using electron back-scattered diffraction（EBSD）. The obtained results show that the surface roughness increased firstly with increasing strain and then decreased slightly. There was a critical strain for aluminum alloy tube, below which ＂orange peel＂ defect would not occur. For the tube with a mean grain size of 80, 105, 130 and 175 μm, the critical strains were 10.17%, 5.74%, 3.15% and 1.62%, respectively. Meanwhile, the surface roughening behavior was produced by serious inhomogeneous deformation between grains as strain increased, and was aggravated as the grain size increased due to the larger local deformation in larger grains.
文摘To study the damage and fracture mechanism of 6063 aluminum alloy under different stress states,three kinds of representative triaxial stress states have been adopted,namely smooth tensile,notch tensile,and pure shear.The results of the study indicate the following.During the notch tensile test,a relatively higher stress triaxiality appears in the root of the notch.With the applied loading increasing,the volume fraction of microvoids in the root of the notch increases continuously.When it reaches the critical volume fraction of microvoids,the specimen fractures.During the pure shear test,the stress triaxiality almost equals to zero,and there is almost no microvoids but a shear band at the center of the butterfly specimen.The shear band results from nonuniform deformation constantly under the shear stress.With stress concentration,cracks are produced within the shear band and are later coalesced.When the equivalent plastic strain reaches the critical value（equivalent plastic fracture strain）,the butterfly specimen fractures.During the smooth tensile test,the stress triaxiality in the gauge of the specimen remains constant at 0.33.Thus,the volume of microvoids of the smooth tensile test is less than that of the notch tensile test and the smooth specimen fractures due to shearing between microvoids.The G-T-N damage model and Johnson-Cook model are used to simulate the notch tensile and shear test,respectively.The simulated engineering stress-strain curves fit the measured engineering stress-strain curves very well.In addition,the empirical damage evolution equation for the notch specimen is obtained from the experimental data and FEM simulations.
基金Project(2008A09030004) supported by the Major Science and Technology Project of Guangdong Province,ChinaProject(30815009) supported by the Foundation of State Key Laboratory of Advanced Design and Manufacture for Vehicle Body
文摘The hot compression test of 6063 Al alloy was performed on a Gleeble-1500 thermo-simulation machine, and the forming of 6063 rod cxtrudate in low-temperature high-speed extrusion was simulated with extrusion ratio of 25 on the platform of DEFORM 2D successfully. From the compression experimental results, the flow stress model of this Al alloy is obtained which could be the constitutive equation in the simulation of low-temperature high-speed extrusion process. From the numerical simulation results, there is a higher strain concentration at the entrance of the die and the exit temperature reaches up to 522 ℃ in low-temperature high-speed extrusion, which approaches to the quenching temperature of the 6063 Al alloy. The results show that the low-temperature high-speed extrusion method as a promsing one can reduce energy consumption effectively.
文摘The deformation behavior characteristics of 6063 aluminum alloy were studied experimentally by isothermal compression tests on a Gleeble- 1500 thermal-mechanical simulator. Cylindrical specimens of 14mm in height and 10mm in diameter were compressed dynamically at temperatures ranging from 473 to 723K and at higher strain rntes from 5 to 30s^-1. It is fouud that the flow curves not only depend on the strain rate and temperature but nlso on the dynamic recovery aud recrystallization behavior. The results show that the flow stress decreased with the increase of temperature, while increased with the increase of strain rate. The discontinuous dynamic recrystallization （DDRX） may take place at a high strain rate of 20s^-1 under the tested conditions. At 30s^-1 , the flow curve can exhibit,flow softening due to the effect of temperature rise that raised the temperature by aboat 32K in less than 0.05s.
文摘A two-step ultrasonic-assisted brazing method and its associated apparatus were developed to make 6063 aluminum alloys joints with Al-Si-Mg filler metal. The burst phenomenon and the effect of ultrasonic direction and time, as well as the welding joint geometry on the burst phenomenon were investigated. The results show that the burst phenomenon occurs in the liquid filler metal under the effects of high current density, heat, and interaction force. The burst phenomenon is eliminated when the oxide film on the edge of the cross-section of the two parent metals is removed with more than or equal to 6 s ultrasonic time. A model of formation and elimination for burst was proposed, through which the blasting phenomenon can be controlled by changing the ultrasonic time and the geometrical shape of the welded joint.
基金Funded by the National Natural Science Foundation of China(Nos.51371039 and 51871031)
文摘Plasma electrolytic oxidation(PEO) coatings were fabricated on 6063 aluminum alloy in a cheap and convenient electrolyte. The effect of different current densities, i e, 5, 10, 15, and 20 A/dm2on the microstructure and corrosion behavior of coatings was comprehensively studied by scanning electron microscopy(SEM), stereoscopic microscopy, potentiodynamic polarization and electrochemical impedance spectroscopy(EIS), respectively. It is found that the pore density decreases and the pore size increases with increasing current density. The XRD results show that the coatings are only composed of α-Al2O3and γ-Al2O3. Potentiodynamic polarization test proves that the coating formed under 10 A/dm2possesses the best anticorrosion property. The long time EIS test shows that the coating under 10 A/dm2is able to protect the aluminum alloy substrate after long time of immersion in 0.59 M NaCl solution, which confirms the salt solution immersion test results in 2 M NaCl solution.
文摘The present article reports on characterization studies performed on amorphized nanostructured Al 6063 alloy powder synthesized by mechanical alloying (MA). The as-milled powder was characterized by X-ray diffraction (XRD) for investigating the development of crystallite nature and determining the different phases of the materials present, scanning electron microscope (SEM) was used for in depth morphological study and High Resolution-transmission electron microscope (HR-TEM) was employed to ensure the development of a nano-structured nature of the Al 6063 matrix. In the present work alloyed powder was milled for 20 h and 40 h at 300 rpm;and 20 h at 700 rpm in a hardened stainless steel medium. Using Williamson-Hall equation;crystallite size, lattice strain and lattice parameter of Al 6063 nanostructure alloy powder was estimated with broadening of XRD peaks. XRD results showed that the crystallite size of Al 6063 alloy powder reached 32 and 53 nm after 20 h at 700 rpm and 40 h at 300 rpm respectively.
