The influence of sodium silicate on the corrosion behaviour of aluminium alloy 7075-T6 in 0.1 M sodium chloride solution was studied by open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) tec...The influence of sodium silicate on the corrosion behaviour of aluminium alloy 7075-T6 in 0.1 M sodium chloride solution was studied by open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) techniques. Scanning electron microscopy (SEM) was used to characterize the AA7075-T6 surface. Silicate can significantly reduce corrosion deterioration and the inhibition efficiency increases with the concentration of Na<sub>2</sub>SiO<sub>3</sub>. The corrosion inhibition mechanism involves the formation of a protective film over the alloy surface by adsorption of aluminosilicate anions from solution, as has also been suggested by others in literature.展开更多
Asymmetric rolling （ASR）, as one of severe plastic deformation （SPD） methods to make ultra-fine materials with enhanced performance is mainly used to prepare foil and thin strip. The asymmetrical rolling was achie...Asymmetric rolling （ASR）, as one of severe plastic deformation （SPD） methods to make ultra-fine materials with enhanced performance is mainly used to prepare foil and thin strip. The asymmetrical rolling was achieved by adjusting the diameters of the upper roll and the bottom roll and was used to prepare hot-rolled thick plate of 5182 aluminium alloy. The shear deformation and plate shape control were experimentally studied. The experimental results show that asymmetrical rolling has a significant effect on metal deformation stream and can somehow refine microstructure and improve the uniformity of microstructure and properties. The asymmetrical rolling process can also reduce the rolling force. However, bending of rolling plate often happens during asymmetrical rolling process. The factors affecting the bending were discussed.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
Thin copper sheets as marker material were embedded into weld path of 2024 aluminium alloy plates and their final position after friction stir welding was examined by metallographic techniques. Referring to the visual...Thin copper sheets as marker material were embedded into weld path of 2024 aluminium alloy plates and their final position after friction stir welding was examined by metallographic techniques. Referring to the visualized material flow patterns, a three-dimensional model was developed to conduct the numerical simulation of the temperature profile and plastic material flow in friction stir welding. The calculated velocity contour of plastic flow in close proximity of the tool is generally consistent with the visualized results. As the tool rotation speed increases at a constant tool travel speed, the material flow near the pin gets stronger. The predicted shape and size of the weld nugget zone match with the experimentally measured ones.展开更多
Fatigue characteristics of A7N01 aluminium alloy welded joint were investigated and a fatigue crack initiation life-based model was proposed. The difference of fatigue crack initiation life among base metal, weld meta...Fatigue characteristics of A7N01 aluminium alloy welded joint were investigated and a fatigue crack initiation life-based model was proposed. The difference of fatigue crack initiation life among base metal, weld metal and heat affected zone (HAZ) is slight. Furthermore, the ratio of fatigue crack initiation life (Ni) to fatigue life to failure(Nf) is a material dependent parameter, 26.32%, 40.21% and 60.67% for base metal, HAZ and weld metal, respectively. Total fatigue life predicted using the presented model is in good agreement with the experimental data and that using Basquin’s model. The observation results of fatigue fracture surfaces, using scanning electron microscope (SEM), demonstrate that fatigue crack initiates from smooth surface due to welding process for weld metal, blowhole in HAZ causes fatigue crack initiation, and the crushed second phase particles play an important part in fatigue crack initiation in base metal.展开更多
The effects of pre-stretching following solution treatment on the hardness and microstructures of aged 2524 aluminium alloy at 170 ℃ were studied.Ageing hardness values under different pre-stretching conditions were ...The effects of pre-stretching following solution treatment on the hardness and microstructures of aged 2524 aluminium alloy at 170 ℃ were studied.Ageing hardness values under different pre-stretching conditions were measured,and the corresponding microstructures were characterized by transmission electron microscopy（TEM）.The results show that compared with unstretched samples,the peak hardness is increased and the time to reach the peak hardness is reduced with the increase of pre-strain;the number density of S（Al2CuMg） phases is increased and the length is shortened in pre-stretched alloy.Additionally,the number density of GPB zones is decreased with the increase of pre-strain in peak-aged samples.When the pre-strain is up to 5%,S phases play the predominant contribution to the peak hardness.Fine and uniformly distributed S phases lead to a higher hardness than GPB zones together with S phases existing in conventionally aged 2524 alloy.展开更多
Low frequency electromagnetic casting （LFEC） process with the application of an induction coil outside the conventional direct chill （DC） casting mould was used to prepare the flat ingot of 2524 alloy and the effe...Low frequency electromagnetic casting （LFEC） process with the application of an induction coil outside the conventional direct chill （DC） casting mould was used to prepare the flat ingot of 2524 alloy and the effect of electromagnetic field on the microstructure and macrosegregation of this alloy was systematically studied. The results show that the fiat ingot prepared by the LFEC process has a finer and more uniform as-cast microstructure and the grain morphology is transformed from dendrite and rosette-like to equiaxed structure. The LFEC process also shows a significant effect on macrosegregation, and with the application of electromagnetic field during casting process, the segregation in the centre of the ingot is obviously reduced. The mechanism of these effects was also discussed.展开更多
AA2219 aluminium alloy joints were fabricated by variable polarity tungsten inert gas （VPTIG） welding process and the effects of post weld heat treatment （PWHT） on the tensile properties, microstructure and fatigu...AA2219 aluminium alloy joints were fabricated by variable polarity tungsten inert gas （VPTIG） welding process and the effects of post weld heat treatment （PWHT） on the tensile properties, microstructure and fatigue behaviour of the welded joints were investigated. The VPTIG welding process was adopted because it could meet the need of cathode cleaning and meanwhile it could reduce the deterioration of tungsten electrode furthest. The welded samples were divided into as-welded （AW） sample and PWHT sample. The PWHT method used on the samples was solution treatment （535 ℃, 30 rain）, water quenching and artificial aging （175 ℃, 12 h）. The experimental results show that, compared with the AW samples, the microstructure characteristics and mechanical properties of the AA2219 joints after PWHT were significantly improved. The improvement of yield strength, ultimate tensile strength, and fatigue strength are 42.6%, 43.1% and 18.4%, respectively.展开更多
The 7xxx series alloys are heat treatable wrought aluminium alloys based on the Al-Zn-Mg（-Cu） system. They are widely used in high-performance structural aerospace and transportation applications. Apart from composi...The 7xxx series alloys are heat treatable wrought aluminium alloys based on the Al-Zn-Mg（-Cu） system. They are widely used in high-performance structural aerospace and transportation applications. Apart from compositional, casting and thermo-mechanical processing effects, the balance of properties is also significantly influenced by the way in which the materials are heat-treated. This paper describes the effects of homogenisation, solution treatment, quenching and ageing treatments on the evolution of the microstructure and properties of some important medium to high-strength 7xxx alloys. With a focus on recent work at Monash University, where the whole processing route from homogenisation to final ageing has been studied for thick plate products, it is reported how microstructural features such as dispersoids, coarse constituent particles, fine-scale precipitates, grain structure and grain boundary characteristics can be controlled by heat treatment to achieve improved microstructure-property combinations. In particular, the paper presents methods for dissolving unwanted coarse constituent particles by controlled high- temperature treatments, quench sensitivity evaluations based on a systematic study of continuous cooling precipitation behaviour, and ageing investigations of one-, two- and three-step ageing treatments using experimental and modelling approaches, in each case, the effects on both the microstructure and the resulting properties are discussed.展开更多
To obtain flow behavior and workability of 7055 aluminium alloy during hot deformation,hot compression tests at different temperatures and strain rates are conducted.True stress?strain curves of 7055 aluminium alloy u...To obtain flow behavior and workability of 7055 aluminium alloy during hot deformation,hot compression tests at different temperatures and strain rates are conducted.True stress?strain curves of 7055 aluminium alloy under different conditions are obtained and the flow stress increases with ascending strain rate and descending temperature.For Arrhenius constitutive equation,each material parameter is set as a constant,which will bring forth large error for predicting flow behavior.In this work,material parameters are fitted as a function of temperature or strain rate based on experimental results and a modified constitutive equation is established for more accurate prediction of flow behavior of 7055 aluminium alloy.The effects of temperature and strain rate on power dissipation and instability are analyzed to establish a processing map of 7055 aluminium alloy.The dominant deformation mechanism for microstructure evolution at different deformation conditions can be determined and high efficiency of power dissipation may be achieved from power dissipation map.Meanwhile,proper processing parameters to avoid flow instability can be easily acquired in instability map.According to the processing map,optimized processing parameters of 7055 aluminium alloy are temperature of 673?723 K and strain rate of 0.01?0.4 s^?1,during which its efficiency of power dissipation is over 30%.Finite element method(FEM)is used to obtain optimized parameter in hot rolling process on the basis of processing map.展开更多
AA2219 aluminium alloy square butt joints without filler metal addition were fabricated using gas tungsten arc welding （GTAW）, electron beam welding （EBW） and friction stir welding （FSW） processes. The effects o...AA2219 aluminium alloy square butt joints without filler metal addition were fabricated using gas tungsten arc welding （GTAW）, electron beam welding （EBW） and friction stir welding （FSW） processes. The effects of three welding processes on the tensile, fatigue and corrosion behaviour were studied. Microstructure analysis was carried out using optical and electron microscopes. The results show that the FSW joints exhibit superior tensile and fatigue properties compared to EBW and GTAW joints. It is also found that the friction stir welds show lower corrosion resistance than EB and GTA welds. This is mainly due to the presence of finer grains and uniform distribution of strengthening precipitates in the weld metal of FSW joints.展开更多
The conversion coating was formed by dipping AA6061 in a fluorotitanate/zirconate acid and amino trimethylene phosphonic acid （ATMP） solution at room temperature. The formation process and the anti-corrosion perform...The conversion coating was formed by dipping AA6061 in a fluorotitanate/zirconate acid and amino trimethylene phosphonic acid （ATMP） solution at room temperature. The formation process and the anti-corrosion performance of the conversion coating were investigated using electrochemical test and salt spray test （SST）, respectively. The electrochemical test shows that the Zr/Ti and ATMP coating improves the corrosion resistance of AA6061 as good as the chromate （VI） coating. But the results of SST show that the corrosion resistance of Zr/Ti and ATMP coating is not as good as the chromate （VI） coating. The corrosion area is less than 2% after 72 h.展开更多
Friction welding （FW） is a process of solid state joining which is used extensively in recent years due to its advantages such as low heat input,production efficiency,ease of manufacture and environment friendliness...Friction welding （FW） is a process of solid state joining which is used extensively in recent years due to its advantages such as low heat input,production efficiency,ease of manufacture and environment friendliness.Friction welding can be used to join different types of ferrous metals and non-ferrous metals that cannot be welded by traditional fusion welding processes.The process parameters such as friction pressure,forging force,friction time and forging time play the major roles in determining the strength of the joints.In this investigation an attempt was made to develop an empirical relationship to predict the tensile strength of friction welded AA 6082 aluminium alloy and AISI 304 austenitic stainless steels joints,incorporating above said parameters.Response surface methodology （RSM） was applied to optimizing the friction welding process parameters to attain the maximum tensile strength of the joint.展开更多
Pulse laser welding of 0.6 mm-thick AA5052-H32 was performed to determine the optimum set of parameters including laser pulse current,pulse frequency and pulse duration that meets the AWS D17.1 specifications for aero...Pulse laser welding of 0.6 mm-thick AA5052-H32 was performed to determine the optimum set of parameters including laser pulse current,pulse frequency and pulse duration that meets the AWS D17.1 specifications for aerospace industry.The microstructure and mechanical properties of the weldments were also investigated.Relationships between the parameters and weld bead geometry were found.High quality weld joints without solidification crack that met AWS D17.1 requirements were obtained at(I)high pulse energy(25 J)and high average peak power(4.2 kW)and(II)low pulse energy(17.6 J)and low average peak power(2.8 kW).The weld joint formed at lower heat energy input exhibited finer dendritic grain structure.Mg vapourisation and hard phase compound(Al0.5Fe3Si0.5)formation decreased in the weld joint formed at lower heat energy input.Consequently,the tensile strength of the weldment formed at lower heat energy input(168 MPa)is by a factor of 1.15 higher but showed^29%decrease in hardness(111 HV0.1)at the joint when being compared with the weldment formed at higher heat energy input.Appropriate parameters selection is critical to obtaining 0.6 mm-thick AA5052-H32 pulse laser weld joints that meet AWS D17.1 requirements for aircraft structures.展开更多
A new method of quantitative pre-corrosion damage of aviation aluminium(Al-Cu-Mg)alloy was proposed,whichregarded corrosion pits as equivalent semi-elliptical surface cracks.An analytical model was formulated to descr...A new method of quantitative pre-corrosion damage of aviation aluminium(Al-Cu-Mg)alloy was proposed,whichregarded corrosion pits as equivalent semi-elliptical surface cracks.An analytical model was formulated to describe the entire regionof fatigue crack propagation(FCP).The relationship between the model parameters and the fatigue testing data obtained in thepre-corroded experiments,crack propagation experiments and S-N fatigue experiments was discussed.The equivalent crack sizesand the FCP equation were used to calculate the fatigue life through numerical integration based on MATLAB/GUI.The resultsconfirm that the sigmoidal curve fitted by the FCP model expresses the whole change from Region I to Region III.In addition,thepredicted curves indicate the actual trend of fatigue life and the conservative result of fatigue limit.Thus,the new analytical methodcan estimate the residual life of pre-corroded Al-Cu-Mg alloy,especially smooth specimens.展开更多
The effect of cerium salt as an inhibitor in anodising of the2024-T3aluminium alloy was studied.Scanning electronmicroscopy equipped with energy dispersive X-ray spectroscopy was used to study the surface composition ...The effect of cerium salt as an inhibitor in anodising of the2024-T3aluminium alloy was studied.Scanning electronmicroscopy equipped with energy dispersive X-ray spectroscopy was used to study the surface composition of the alloy before andafter surface preparation.A mixed electrolyte of10%sulphuric acid,5%boric acid and2%phosphoric acid containing0.1mol/Lcerium sulphate salt was used as the anodising electrolyte.Sealing treatment was also done in boiling water and molten stearic acid.Electrochemical impedance spectroscopy and salt spray techniques were performed in order to investigate the corrosion behaviourand durability of the oxide films,respectively.It was concluded that the presence of cerium ions in anodising electrolyte resulted inthe increase in homogeneity,the rate of oxide film growth and also the thickness of the oxide layer,owing to the high oxidisingpower of cerium ion.展开更多
Solidification experiments were carried out to investigate the kinetic behaviour of TiB2 particles in Al melt and their effect on the grain refinement of commercially-pure Al.A model was proposed to describe the kinet...Solidification experiments were carried out to investigate the kinetic behaviour of TiB2 particles in Al melt and their effect on the grain refinement of commercially-pure Al.A model was proposed to describe the kinetic behaviour of TiB2 particles during the whole process from the addition of TiB2 to the melt to the freezing of the melt.The results indicate that TiB2 particles are not stable in Al melt.They may dissolve and coarsen during the holding period and grow during the cooling period of the melt.The kinetic behaviour of TiB2 particles in the melt has a great influence on their number density and the grain refinement.Solute Ti addition can suppress the dissolution,Ostwald ripening and growth behaviours of TiB2 particles.展开更多
The hot deformation behavior of AA6063 aluminium alloy has been investigated by means of compression tests at temperatures between 400 and 520℃, and strain rates ranging from 2.5 to 10 s^-1. Owing to the barreling, t...The hot deformation behavior of AA6063 aluminium alloy has been investigated by means of compression tests at temperatures between 400 and 520℃, and strain rates ranging from 2.5 to 10 s^-1. Owing to the barreling, the theoretical model on the basis of Hills general method is used to calculate the flow stress of a cylindrical specimen under uniaxial simple compression so as to consider the friction effect at the die-specimen interface. A method of evaluating the friction coefficient by combining compression tests with the finite element method is presented. The real flow behavior of AA6063 aluminium alloy can be described with sinh-Arrhenius equation. The hot deformation activation energy Q derived from the corrected stress and strain data is 232. 350 kJ/mol.展开更多
Friction stir welding(FSW) is a promising welding process that can join age hardenable aluminium alloys with high joint efficiency. However,the thermal cycles experienced by the material to be joined during FSW result...Friction stir welding(FSW) is a promising welding process that can join age hardenable aluminium alloys with high joint efficiency. However,the thermal cycles experienced by the material to be joined during FSW resulted in the deterioration of mechanical properties due to the coarsening and dissolution of strengthening precipitates in the thermo-mechanical affected zone(TMAZ) and heat affected zone(HAZ). Under water friction stir welding(UWFSW) is a variant of FSW process which can maintain low heat input as well as constant heat input along the weld line. The heat conduction and dissipation during UWFSW controls the width of TMAZ and HAZ and also improves the joint properties. In this investigation, an attempt has been made to evaluate the mechanical properties and microstructural characteristics of AA2519-T87 aluminium alloy joints made by FSW and UWFSW processes. Finite element analysis has been used to estimate the temperature distribution and width of TMAZ region in both the joints and the results have been compared with experimental results and subsequently correlated with mechanical properties.? 2016 China Ordnance Society. Production and hosting by Elsevier B.V. All rights reserved.展开更多
Aluminium alloy（AA） 2024 is an important engineering material due to its widespread use in the aerospace industry. However, it is very prone to corrosion attack in chloride containing media. In the present investiga...Aluminium alloy（AA） 2024 is an important engineering material due to its widespread use in the aerospace industry. However, it is very prone to corrosion attack in chloride containing media. In the present investigation, AA2024 aluminium alloy rolled plates of 5 mm in thickness were friction stir welded. Corrosion performances of the specimens were evaluated by conducting salt fog tests in Na Cl solution at different p H values, chloride ion concentrations and spraying time. In addition, an empirical relationship was established to predict the corrosion rate of friction stir welds of AA2024 aluminium alloy. A central composite rotatable design including three factors and five levels was used to minimize the number of experiments. Response surface methodology（RSM） was used to develop the relationship. The corrosion rate decreased under neutral p H conditions. The corrosion rate increased in acidic and basic conditions. It was also found that the corrosion rate decreased with the increase of spraying time, but the corrosion tended to be uniform with the increment of time and with the increase in the chloride ion concentration, and the corrosion rate increased in the salt spray corrosion test.展开更多
文摘The influence of sodium silicate on the corrosion behaviour of aluminium alloy 7075-T6 in 0.1 M sodium chloride solution was studied by open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) techniques. Scanning electron microscopy (SEM) was used to characterize the AA7075-T6 surface. Silicate can significantly reduce corrosion deterioration and the inhibition efficiency increases with the concentration of Na<sub>2</sub>SiO<sub>3</sub>. The corrosion inhibition mechanism involves the formation of a protective film over the alloy surface by adsorption of aluminosilicate anions from solution, as has also been suggested by others in literature.
基金Projects(51104043,51374067)supported by the National Natural Science Foundation of ChinaProject(2012CB619506)supported by the National Basic Research Program of ChinaProject(N120409002)supported by the Fundamental Research Funds for the Central Universities,China
文摘Asymmetric rolling （ASR）, as one of severe plastic deformation （SPD） methods to make ultra-fine materials with enhanced performance is mainly used to prepare foil and thin strip. The asymmetrical rolling was achieved by adjusting the diameters of the upper roll and the bottom roll and was used to prepare hot-rolled thick plate of 5182 aluminium alloy. The shear deformation and plate shape control were experimentally studied. The experimental results show that asymmetrical rolling has a significant effect on metal deformation stream and can somehow refine microstructure and improve the uniformity of microstructure and properties. The asymmetrical rolling process can also reduce the rolling force. However, bending of rolling plate often happens during asymmetrical rolling process. The factors affecting the bending were discussed.
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Project (GZ583) supported by the Sino-German Center for Science Promotion
文摘Thin copper sheets as marker material were embedded into weld path of 2024 aluminium alloy plates and their final position after friction stir welding was examined by metallographic techniques. Referring to the visualized material flow patterns, a three-dimensional model was developed to conduct the numerical simulation of the temperature profile and plastic material flow in friction stir welding. The calculated velocity contour of plastic flow in close proximity of the tool is generally consistent with the visualized results. As the tool rotation speed increases at a constant tool travel speed, the material flow near the pin gets stronger. The predicted shape and size of the weld nugget zone match with the experimentally measured ones.
文摘Fatigue characteristics of A7N01 aluminium alloy welded joint were investigated and a fatigue crack initiation life-based model was proposed. The difference of fatigue crack initiation life among base metal, weld metal and heat affected zone (HAZ) is slight. Furthermore, the ratio of fatigue crack initiation life (Ni) to fatigue life to failure(Nf) is a material dependent parameter, 26.32%, 40.21% and 60.67% for base metal, HAZ and weld metal, respectively. Total fatigue life predicted using the presented model is in good agreement with the experimental data and that using Basquin’s model. The observation results of fatigue fracture surfaces, using scanning electron microscope (SEM), demonstrate that fatigue crack initiates from smooth surface due to welding process for weld metal, blowhole in HAZ causes fatigue crack initiation, and the crushed second phase particles play an important part in fatigue crack initiation in base metal.
基金Project(51001022) supported by the National Natural Science Foundation of ChinaProject supported by Innovative Research Team in University of Liaoning Province,China
文摘The effects of pre-stretching following solution treatment on the hardness and microstructures of aged 2524 aluminium alloy at 170 ℃ were studied.Ageing hardness values under different pre-stretching conditions were measured,and the corresponding microstructures were characterized by transmission electron microscopy（TEM）.The results show that compared with unstretched samples,the peak hardness is increased and the time to reach the peak hardness is reduced with the increase of pre-strain;the number density of S（Al2CuMg） phases is increased and the length is shortened in pre-stretched alloy.Additionally,the number density of GPB zones is decreased with the increase of pre-strain in peak-aged samples.When the pre-strain is up to 5%,S phases play the predominant contribution to the peak hardness.Fine and uniformly distributed S phases lead to a higher hardness than GPB zones together with S phases existing in conventionally aged 2524 alloy.
基金Projects(51104043,51374067)supported by the National Natural Science Foundation of ChinaProject(2012CB619506)supported by the National Basic Research Program of ChinaProject(N120409002)supported by the Fundamental Research Funds for the Central Universities,China
文摘Low frequency electromagnetic casting （LFEC） process with the application of an induction coil outside the conventional direct chill （DC） casting mould was used to prepare the flat ingot of 2524 alloy and the effect of electromagnetic field on the microstructure and macrosegregation of this alloy was systematically studied. The results show that the fiat ingot prepared by the LFEC process has a finer and more uniform as-cast microstructure and the grain morphology is transformed from dendrite and rosette-like to equiaxed structure. The LFEC process also shows a significant effect on macrosegregation, and with the application of electromagnetic field during casting process, the segregation in the centre of the ingot is obviously reduced. The mechanism of these effects was also discussed.
基金Project(51275343)supported by the National Natural Science Foundation of China
文摘AA2219 aluminium alloy joints were fabricated by variable polarity tungsten inert gas （VPTIG） welding process and the effects of post weld heat treatment （PWHT） on the tensile properties, microstructure and fatigue behaviour of the welded joints were investigated. The VPTIG welding process was adopted because it could meet the need of cathode cleaning and meanwhile it could reduce the deterioration of tungsten electrode furthest. The welded samples were divided into as-welded （AW） sample and PWHT sample. The PWHT method used on the samples was solution treatment （535 ℃, 30 rain）, water quenching and artificial aging （175 ℃, 12 h）. The experimental results show that, compared with the AW samples, the microstructure characteristics and mechanical properties of the AA2219 joints after PWHT were significantly improved. The improvement of yield strength, ultimate tensile strength, and fatigue strength are 42.6%, 43.1% and 18.4%, respectively.
基金The Aluminium Corporation of China Ltd.(Chalco)for supporting aspects of this work financiallyproviding AA7150 materials as part of the Australia-China International Centre for Light Alloy Research(ICLAR)+1 种基金Monash University for developing the retrogression and reageing Matlab model (as part of the PhD project of Dr Adrian GROSVENOR)The ARC Centre of Excellence for Design in Light Metals and its Directors (first Prof Barry MUDDLE and then Prof Xin-hua WU) for supporting
文摘The 7xxx series alloys are heat treatable wrought aluminium alloys based on the Al-Zn-Mg（-Cu） system. They are widely used in high-performance structural aerospace and transportation applications. Apart from compositional, casting and thermo-mechanical processing effects, the balance of properties is also significantly influenced by the way in which the materials are heat-treated. This paper describes the effects of homogenisation, solution treatment, quenching and ageing treatments on the evolution of the microstructure and properties of some important medium to high-strength 7xxx alloys. With a focus on recent work at Monash University, where the whole processing route from homogenisation to final ageing has been studied for thick plate products, it is reported how microstructural features such as dispersoids, coarse constituent particles, fine-scale precipitates, grain structure and grain boundary characteristics can be controlled by heat treatment to achieve improved microstructure-property combinations. In particular, the paper presents methods for dissolving unwanted coarse constituent particles by controlled high- temperature treatments, quench sensitivity evaluations based on a systematic study of continuous cooling precipitation behaviour, and ageing investigations of one-, two- and three-step ageing treatments using experimental and modelling approaches, in each case, the effects on both the microstructure and the resulting properties are discussed.
基金Project(51175257)supported by National Natural Science Foundation of ChinaProject(BK20170785)supported by the Natural Science Foundation of Jiangsu Province,China+1 种基金Project(BE2016179)supported by Science and Technology Planning Project of Jiangsu Province,ChinaProject(Kfkt2017-08)supported by Open Research Fund of State Key Laboratory for High Performance Complex Manufacturing,Central South University,China
文摘To obtain flow behavior and workability of 7055 aluminium alloy during hot deformation,hot compression tests at different temperatures and strain rates are conducted.True stress?strain curves of 7055 aluminium alloy under different conditions are obtained and the flow stress increases with ascending strain rate and descending temperature.For Arrhenius constitutive equation,each material parameter is set as a constant,which will bring forth large error for predicting flow behavior.In this work,material parameters are fitted as a function of temperature or strain rate based on experimental results and a modified constitutive equation is established for more accurate prediction of flow behavior of 7055 aluminium alloy.The effects of temperature and strain rate on power dissipation and instability are analyzed to establish a processing map of 7055 aluminium alloy.The dominant deformation mechanism for microstructure evolution at different deformation conditions can be determined and high efficiency of power dissipation may be achieved from power dissipation map.Meanwhile,proper processing parameters to avoid flow instability can be easily acquired in instability map.According to the processing map,optimized processing parameters of 7055 aluminium alloy are temperature of 673?723 K and strain rate of 0.01?0.4 s^?1,during which its efficiency of power dissipation is over 30%.Finite element method(FEM)is used to obtain optimized parameter in hot rolling process on the basis of processing map.
基金Project DRAO/08/1061356/M1 supported by Aeronautical Research & Development Board (ARDB),New Delhi,India
文摘AA2219 aluminium alloy square butt joints without filler metal addition were fabricated using gas tungsten arc welding （GTAW）, electron beam welding （EBW） and friction stir welding （FSW） processes. The effects of three welding processes on the tensile, fatigue and corrosion behaviour were studied. Microstructure analysis was carried out using optical and electron microscopes. The results show that the FSW joints exhibit superior tensile and fatigue properties compared to EBW and GTAW joints. It is also found that the friction stir welds show lower corrosion resistance than EB and GTA welds. This is mainly due to the presence of finer grains and uniform distribution of strengthening precipitates in the weld metal of FSW joints.
基金supported by the Science and Technology Plan Project of Liaoning Province,China(No.2006221011).
文摘The conversion coating was formed by dipping AA6061 in a fluorotitanate/zirconate acid and amino trimethylene phosphonic acid （ATMP） solution at room temperature. The formation process and the anti-corrosion performance of the conversion coating were investigated using electrochemical test and salt spray test （SST）, respectively. The electrochemical test shows that the Zr/Ti and ATMP coating improves the corrosion resistance of AA6061 as good as the chromate （VI） coating. But the results of SST show that the corrosion resistance of Zr/Ti and ATMP coating is not as good as the chromate （VI） coating. The corrosion area is less than 2% after 72 h.
文摘Friction welding （FW） is a process of solid state joining which is used extensively in recent years due to its advantages such as low heat input,production efficiency,ease of manufacture and environment friendliness.Friction welding can be used to join different types of ferrous metals and non-ferrous metals that cannot be welded by traditional fusion welding processes.The process parameters such as friction pressure,forging force,friction time and forging time play the major roles in determining the strength of the joints.In this investigation an attempt was made to develop an empirical relationship to predict the tensile strength of friction welded AA 6082 aluminium alloy and AISI 304 austenitic stainless steels joints,incorporating above said parameters.Response surface methodology （RSM） was applied to optimizing the friction welding process parameters to attain the maximum tensile strength of the joint.
基金the funding (UniversityIndustry Engagement Grant)support provided by the Universiti Sains Malaysia under the Teaching Fellowship Scheme
文摘Pulse laser welding of 0.6 mm-thick AA5052-H32 was performed to determine the optimum set of parameters including laser pulse current,pulse frequency and pulse duration that meets the AWS D17.1 specifications for aerospace industry.The microstructure and mechanical properties of the weldments were also investigated.Relationships between the parameters and weld bead geometry were found.High quality weld joints without solidification crack that met AWS D17.1 requirements were obtained at(I)high pulse energy(25 J)and high average peak power(4.2 kW)and(II)low pulse energy(17.6 J)and low average peak power(2.8 kW).The weld joint formed at lower heat energy input exhibited finer dendritic grain structure.Mg vapourisation and hard phase compound(Al0.5Fe3Si0.5)formation decreased in the weld joint formed at lower heat energy input.Consequently,the tensile strength of the weldment formed at lower heat energy input(168 MPa)is by a factor of 1.15 higher but showed^29%decrease in hardness(111 HV0.1)at the joint when being compared with the weldment formed at higher heat energy input.Appropriate parameters selection is critical to obtaining 0.6 mm-thick AA5052-H32 pulse laser weld joints that meet AWS D17.1 requirements for aircraft structures.
基金Project(SHSYS2015002) supported by the Key Laboratory of Fundamental Science for National Defence of Aeronautical Digital Manufacturing Process,China
文摘A new method of quantitative pre-corrosion damage of aviation aluminium(Al-Cu-Mg)alloy was proposed,whichregarded corrosion pits as equivalent semi-elliptical surface cracks.An analytical model was formulated to describe the entire regionof fatigue crack propagation(FCP).The relationship between the model parameters and the fatigue testing data obtained in thepre-corroded experiments,crack propagation experiments and S-N fatigue experiments was discussed.The equivalent crack sizesand the FCP equation were used to calculate the fatigue life through numerical integration based on MATLAB/GUI.The resultsconfirm that the sigmoidal curve fitted by the FCP model expresses the whole change from Region I to Region III.In addition,thepredicted curves indicate the actual trend of fatigue life and the conservative result of fatigue limit.Thus,the new analytical methodcan estimate the residual life of pre-corroded Al-Cu-Mg alloy,especially smooth specimens.
文摘The effect of cerium salt as an inhibitor in anodising of the2024-T3aluminium alloy was studied.Scanning electronmicroscopy equipped with energy dispersive X-ray spectroscopy was used to study the surface composition of the alloy before andafter surface preparation.A mixed electrolyte of10%sulphuric acid,5%boric acid and2%phosphoric acid containing0.1mol/Lcerium sulphate salt was used as the anodising electrolyte.Sealing treatment was also done in boiling water and molten stearic acid.Electrochemical impedance spectroscopy and salt spray techniques were performed in order to investigate the corrosion behaviourand durability of the oxide films,respectively.It was concluded that the presence of cerium ions in anodising electrolyte resulted inthe increase in homogeneity,the rate of oxide film growth and also the thickness of the oxide layer,owing to the high oxidisingpower of cerium ion.
基金Projects(51901231,51971227,51771210,51774264)supported by the National Natural Science Foundation of ChinaProject(2019-BS-253)supported by the Natural Science Foundation of Liaoning Province,China。
文摘Solidification experiments were carried out to investigate the kinetic behaviour of TiB2 particles in Al melt and their effect on the grain refinement of commercially-pure Al.A model was proposed to describe the kinetic behaviour of TiB2 particles during the whole process from the addition of TiB2 to the melt to the freezing of the melt.The results indicate that TiB2 particles are not stable in Al melt.They may dissolve and coarsen during the holding period and grow during the cooling period of the melt.The kinetic behaviour of TiB2 particles in the melt has a great influence on their number density and the grain refinement.Solute Ti addition can suppress the dissolution,Ostwald ripening and growth behaviours of TiB2 particles.
基金supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars of Shanxi Province of China (No.9835).
文摘The hot deformation behavior of AA6063 aluminium alloy has been investigated by means of compression tests at temperatures between 400 and 520℃, and strain rates ranging from 2.5 to 10 s^-1. Owing to the barreling, the theoretical model on the basis of Hills general method is used to calculate the flow stress of a cylindrical specimen under uniaxial simple compression so as to consider the friction effect at the die-specimen interface. A method of evaluating the friction coefficient by combining compression tests with the finite element method is presented. The real flow behavior of AA6063 aluminium alloy can be described with sinh-Arrhenius equation. The hot deformation activation energy Q derived from the corrected stress and strain data is 232. 350 kJ/mol.
基金the financial support of the Directorate of Extramural Research & Intellectual Property Rights (ER&IPR)Defense Research Development Organization (DRDO)New Delhi through a R&D project no. DRDO-ERIPER/ERIP/ER/0903821/M/01/1404 to carry out this investigation
文摘Friction stir welding(FSW) is a promising welding process that can join age hardenable aluminium alloys with high joint efficiency. However,the thermal cycles experienced by the material to be joined during FSW resulted in the deterioration of mechanical properties due to the coarsening and dissolution of strengthening precipitates in the thermo-mechanical affected zone(TMAZ) and heat affected zone(HAZ). Under water friction stir welding(UWFSW) is a variant of FSW process which can maintain low heat input as well as constant heat input along the weld line. The heat conduction and dissipation during UWFSW controls the width of TMAZ and HAZ and also improves the joint properties. In this investigation, an attempt has been made to evaluate the mechanical properties and microstructural characteristics of AA2519-T87 aluminium alloy joints made by FSW and UWFSW processes. Finite element analysis has been used to estimate the temperature distribution and width of TMAZ region in both the joints and the results have been compared with experimental results and subsequently correlated with mechanical properties.? 2016 China Ordnance Society. Production and hosting by Elsevier B.V. All rights reserved.
文摘Aluminium alloy（AA） 2024 is an important engineering material due to its widespread use in the aerospace industry. However, it is very prone to corrosion attack in chloride containing media. In the present investigation, AA2024 aluminium alloy rolled plates of 5 mm in thickness were friction stir welded. Corrosion performances of the specimens were evaluated by conducting salt fog tests in Na Cl solution at different p H values, chloride ion concentrations and spraying time. In addition, an empirical relationship was established to predict the corrosion rate of friction stir welds of AA2024 aluminium alloy. A central composite rotatable design including three factors and five levels was used to minimize the number of experiments. Response surface methodology（RSM） was used to develop the relationship. The corrosion rate decreased under neutral p H conditions. The corrosion rate increased in acidic and basic conditions. It was also found that the corrosion rate decreased with the increase of spraying time, but the corrosion tended to be uniform with the increment of time and with the increase in the chloride ion concentration, and the corrosion rate increased in the salt spray corrosion test.
