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
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
In the present research work,AZ91 magnesium alloy and AA6082-T6 aluminium alloy were joined by friction stir welding process.The comparison of microstructure and mechanical properties between different joints by varyi...In the present research work,AZ91 magnesium alloy and AA6082-T6 aluminium alloy were joined by friction stir welding process.The comparison of microstructure and mechanical properties between different joints by varying the different materials on advance and retreating sides were mainly studied.Four different welds have been prepared to find the material mixing between the similar and dissimilar joints.The joint interfaces of the welds have been investigated by employing an optical microscope and scanning electron microscope.When Mg was placed on advancing side(AS),more aluminium content was soluble in nugget zone than the case where Mg was placed on the retreating side(RS).Thin intermetallic layer in the joint interface of Mg/Al and thick intermetallic layer with poor adhesion of the aluminium and magnesium have been observed in the dissimilar joints varying the sides.The highest UTS of 172.3 MPa was found for Mg-Al when Mg was placed on AS and lower UTS of 156.25 MPa was obtained when Mg was placed on RS.Hardness of 86 Hv and 89 Hv were observed in the Stir zone for the dissimilar AZ91 Mg alloy and AA6082-T6 Al alloy when AZ91Mg alloy was placed on the AS and on the RS respectively.Fractography was also carried out to find the mode of failure.展开更多
The superplastic deformation of aluminium alloy 7475 applied electric current pulse has been studied.The results presented that applying a high density current pulse raises both the elongation rate and the m value,and...The superplastic deformation of aluminium alloy 7475 applied electric current pulse has been studied.The results presented that applying a high density current pulse raises both the elongation rate and the m value,and makes supperior superplastic properties at high strain rate of 10^(-2)s^(-1),the optimum deformation temperature could move from 530℃to 480~510℃,TEM observation showed the superplastic deformation of the alloy is the results of grain boundary slips and dislocation slips in grains under function of the electron wind;the intergranular tear is a main behavior of fracture of the alloy.展开更多
Rapidly solidified 2024 aluminium alloy powders were mechanically milled, then consolidated to bulk form. The microstructural changes of the powders in mechanical milling (MM) and consolidation process were characteri...Rapidly solidified 2024 aluminium alloy powders were mechanically milled, then consolidated to bulk form. The microstructural changes of the powders in mechanical milling (MM) and consolidation process were characterized by X-ray diffraction analyses and transmission electron microscopy observations. The results showed that mechanical milling reduced the grain size to nanometer, dissolved the Al2Cu intermetallic compound into the aluminium matrix and produced an aluminium supersaturated solid solution. During consolidation process. the grain size increased to submicrometer, and the Al2Cu and Al2(Cu, Mg, Si, Fe, Mn) compounds precipitated owing to heating. Increasing consolidation temperature and time results in obvious grain growth and coarsening of second phase particles. The tensile yield strength of the consolidated alloy with submicrometer size grains increases with decreasing grain size, and it follows the famous HallPetch展开更多
7XXX series aluminium alloys generally present low weldability by fusion welding methods because of the sensitivity to weld solidification cracking, vaporization of strengthening alloys and other defects in the fusion...7XXX series aluminium alloys generally present low weldability by fusion welding methods because of the sensitivity to weld solidification cracking, vaporization of strengthening alloys and other defects in the fusion zone. Friction stir welding(FSW) can be deployed successfully with aluminium alloys. We presented the effect of post-weld heat treatment(PWHT) on the microstructure and mechanical properties of SSM7075 joints. Semi solid plates were butt-welded by FSW at a rotation speed of 1110 r/min, welding speeds of 70 and 110 mm/min. Solution treatment, artificial aging, and T6(solution treatment and artificial aging combined) were applied to the welded joints, each with three samples. It was found that the T6 joints at the speed of 70 mm/min yielded the highest tensile strength of 459.23 MPa. This condition best enhanced the mechanical properties of FSW SSM7075 aluminium alloy joints.展开更多
High strength-to-weight ratio of non-ferrous alloys, such as aluminium, magnesium and titanium alloys, are considered to be possible replacement of widely accepted steels in transportation and automobile sectors. Amon...High strength-to-weight ratio of non-ferrous alloys, such as aluminium, magnesium and titanium alloys, are considered to be possible replacement of widely accepted steels in transportation and automobile sectors. Among these alloys, magnesium is self explosive and titanium is costlier, and aluminium is most likely to replace steels. Application of aluminium or its alloys is also thought of as an appropriate replacement in defence field, especially to enhance the easiness in mobility of combat vehicles while maintaining the same standard as that of conventional armour grade steels. Hence most of the investigations have been confined to aluminium or its alloys as base material and open an era of developing the newer composite materials to address the major limitation, i.e. tribological properties. The surface composites can be fabricated by incorporating the ceramic carbides like silicon carbide, carbides of transition metals and oxides of aluminium using surface modification techniques, such as high energy laser melt treatment, high energy electron beam irradiation and thermal spray process which are based on fusion route. These techniques yield the fusion related problems, such as interfacial reaction, pin holes, shrinkage cavities or voids and other casting related defects, and pave the way to need of an efficient technique which must be based on solid state. Recently developed friction stir processing technique was used in the present investigation for surface modification of AA7075 aluminum alloy, which is an alternative to steels. In the present investigation, 160 μm sized boron carbide powder was procured and was reduced to 60 μm and 30 μm using high energy ball mill. Subsequently these powders were used to fabricate the surface composites using friction stir processing.Ballistic performance testing as per the military standard(JIS.0108.01) was carried out. In the present work, an analytical method of predicting the ballistic behavior of surface composites was developed. This method was based on energy balance, i.e., the initial energy of impact is same as that of energy absorbed by multi layers. An attempt also has been made to validate the analytical results with the experimental findings. Variation between the analytical and experimental results may be accounted due to the assumptions considering such as isotropic behavior of target and shearing area of contact as cylindrical instead of conical interface As the analytical model yields the ballistic performance in the closer proximity of experimentally obtained, it can be considered to be an approximation to evaluate the ballistic performance of targets.展开更多
Residual stress is one of the factors affecting the machining deformation of monolithic structure parts in the aviation industry. Thus,the studies on machining deformation rules induced by residual stresses largely de...Residual stress is one of the factors affecting the machining deformation of monolithic structure parts in the aviation industry. Thus,the studies on machining deformation rules induced by residual stresses largely depend on correctly and efficiently measuring the residual stresses of workpieces. A modified layer-removal method is proposed to measure residual stress by analysing the characteristics of a traditional layer-removal method. The coefficients of strain release are then deduced according to the simulation results using the finite element method( FEM). Moreover,the residual stress in a 7075T651 aluminium alloy plate is measured using the proposed method,and the results are then analyzed and compared with the data obtained by the traditional methods. The analysis indicates that the modified layer-removal method is effective and practical for measuring the residual stress distribution in pre-stretched aluminium alloy plates.展开更多
Commercial aluminium alloy sheets are presently sem ic ontinuously, direct chill casting billets that are hot and cold rolled to the fi nal gauge. Interest has been shown in continuous methods which eliminate the ho t...Commercial aluminium alloy sheets are presently sem ic ontinuously, direct chill casting billets that are hot and cold rolled to the fi nal gauge. Interest has been shown in continuous methods which eliminate the ho t rolling step through rapid solidification of the molten metal to the final sla b. Accordingly, sheets are produced by homogenization, cold rolling, intermedia te and final annealing of these roll-cast slabs. The problem of earing is of gr eat concern as it causes frequent interruption of production runs and leads to m aterial wastage. Therefore, it is quite desirable that earing can be predic ted and consequently necessary measures be taken to minimize or eliminate this u nwanted phenomenon. It is accepted generally that, the principal source of earing is the crystallogr aphic anisotropy arising from non-random distribution of crystal orientations i n the material. Accordingly, several attempts have been made to correlate the m echanical and crystallographic properties of the materials to the earing behavio ur for predictive purposes. Some of these are based on continuum concepts which concentrate on the macroscopic rather than the microscopic aspects of the mater ials. To accommodate the microstructural features of the material, some models have been developed. A more recent approach which provides a connection between texture and plastic anisotropy parameters of the material is the Continuum Mech anics of Textured Polycrystals (CMTP) method proposed by Lin et al. A simplifie d version of this method has been suggested by Chan with promising accuracy for aluminium and copper sheets. AA3105 and AA8011 aluminium alloy sheets were used in this investigation. The a s-cast slabs were cold rolled to the final thickness of 1.0 mm. Different anne aling temperatures in the range of 420 ℃ to 540 ℃ produced a range of R-value s. Circular blanks of 60 mm diameter were machined and deep drawn using a cylind rical flat-bottom punch of 33 mm diameter. The heights of the drawn cups were measured at 0, 45 and 90° to the rolling direction, with the aid of a microme ter accurate to 10 -2 mm. The earing percentage was then calculated usin g the following formula: % earing=h p-h v1/2(h p+h v)(1) where h p is the distance between the bottom of the cup and the peak of ear , and h v is the distance between the bottom of the cup and the valley of t he ear. For the measurement of plastic strain ratios (R-values), tensile specimens cut at 0, 45 and 90° to the rolling direction were photogridded with 1mm square s. These specimens were then stretched in the range of uniform deformation and the dimensional changes were measured with the aid of a travelling microscope. The strain ratios, whether R 0, R 45 or R 90 were determined from the following equation: R θ=dε wdε t=dε wdε l+dε w(2) where Θ refers to the specimen orientation and dε w and dεl refer to the transverse and longitudinal strains of the gauge section, respectively. The av erage strain ratio, R, and the parameter ΔR were then calculated from: R=14(R 0+2R 45+R 90)(3) ΔR=12(R 0-2R 45+R 90)(4) where R 0, R 45 and R 90 values are determined using specimen s cut at 0, 45 and 90° to the rolling direction, respectively. Finally, a continuum mechanics approach using different yield criteria is employ ed for the prediction of earing behaviour under different conditions of the mate rials. Instead of using texture data, the yield stress values are obtained by d ifferent anisotropic yield criteria such as; Hosford, Hill, and Zhou. The predicted earing profiles are compared to the experimental data and the suit ability of different yield criteria is discussed.展开更多
In this study, it is aimed to investigate effect of the grain refinement on the mechanical properties of the AA 6082. The micro structure which plays crucial role in determining the mechanical properties of the alloys...In this study, it is aimed to investigate effect of the grain refinement on the mechanical properties of the AA 6082. The micro structure which plays crucial role in determining the mechanical properties of the alloys is varied according to grain size, chemical composition and cooling rate. The prescription was prepared by determining the chemical composition range according to the standard (TSE-EN-573). The casting experiments were performed on the 6082 aluminium alloy which belongs to Al-Mg-Si system with different percentages of grain refinement (AlTi<sub>5</sub>B<sub>1</sub>) and chemical composition. Heat treatment that is homogenization and artificial aging was applied after casting and extrusion process, respectively. The microstructure analysis and mechanical tests were done on the produced samples in order to understand the structural and mechanical strength of the material. The experimental results showed that using the grain refinements is contributed to increasing the mechanical properties. It was observed that the mechanical strength values increased by 17% after the reduction of the grain size by 69% with the 0.11% addition of the AlTi<sub>5</sub>B<sub>1</sub> master alloy.展开更多
Broad use of lightweight aluminium alloy parts in automobile manufacturing,aerospace,electronic communication,and rail transit is mainly formed through deep drawing process.Deep drawing friction is a key boundary cond...Broad use of lightweight aluminium alloy parts in automobile manufacturing,aerospace,electronic communication,and rail transit is mainly formed through deep drawing process.Deep drawing friction is a key boundary condition for controlling the forming quality of aluminium alloy parts.However,due to the oxidation and adhesion tendency of aluminium alloys,the tribological situations of aluminium alloy deep drawing(AADD)system is more complicated than those of traditional deep drawing of steel sheets.Therefore,the study of AADD friction is essential for manufacturing high-performance aluminium alloy parts.Herein,aiming to provide a valuable reference for researchers in related fields,a comprehensive review of AADD friction is provided,including friction mechanism,influencing factors,friction measurement,friction model,friction simulation,and lubrication-free friction control.Finally,a brief conclusion and several current challenges were discussed.展开更多
In the aerospace industry,integrated aluminium alloy plates and stiffened panels with high accuracy and performance attract significant interest.To manufacture these panels as integrity with high accuracy,multiple pro...In the aerospace industry,integrated aluminium alloy plates and stiffened panels with high accuracy and performance attract significant interest.To manufacture these panels as integrity with high accuracy,multiple processes need to be utilised,such as machining,welding and forming.During the whole manufacturing chain,residual stresses can be generated and redistributed in the components among different processes.The residual stress would significantly affect the shapes and properties of the final products.Currently,these great effects are not well considered in the design and manufacturing processes.This paper aims to draw a general understanding of the residual stress generated in the pre-manufacturing processes and its effects on subsequent manufacturing processes.The mechanisms and distributions of residual stresses generated in typical premanufacturing processes of structural panels,including machining,welding and additive manufacturing(AM),are firstly summarised.The detailed effects of generated residual stresses on distortion and application properties in subsequent manufacturing processes are then concluded.In addition,current methods developed for the investigation of residual stress effect in multi-processes manufacturing are critically reviewed,including experimental,analytical,finite element(FE)and machine learning methods.Furthermore,the future development trend of methods for residual stress consideration and control in the design of manufacturing processes is summarised,providing comprehensive guidance to achieve the high accurate manufacturing of aluminium alloy structural components.展开更多
The quenching-induced residual stress in ultrahigh strength Al-Zn-Mg-Cu alloys has a great influence on their precipitation behaviour in subsequent heat treatment and the properties of the final products.In the presen...The quenching-induced residual stress in ultrahigh strength Al-Zn-Mg-Cu alloys has a great influence on their precipitation behaviour in subsequent heat treatment and the properties of the final products.In the present work,the cladding quenching method was employed for 7085 Al alloy slabs to tailor different quenching residual stresses.Then the effects of quenching residual stress on the precipitation behaviour of the 7085 Al alloy were investigated through finite element analysis,residual stress and hardness distri-bution measurements and microstructural examinations.The results indicate that the reduction in resid-ual stress increases with increasing cladding layer thickness.For a cladding layer thickness in the range of 1-1.4 mm,the residual stress is almost eliminated.The hardness at the surface of the aged sample with a large compressive residual stress is decreased,while the hardness at the centre of the sample with a large tensile residual stress is increased.The hardness is approximately identical between the aged sam-ples with little or no residual stress.The elastic lattice distortion caused by residual stress is found to promote the nucleation of precipitates during the artificial ageing process.The in-depth mechanisms for the effect of quenching residual stress on the precipitation of 7085 Al alloy are also discussed.展开更多
The main objective of this research was to examine the suitability of aluminium alloy to design a piston of an internal combustion engine for improvement in weight and cost reduction. The piston was modelled using Aut...The main objective of this research was to examine the suitability of aluminium alloy to design a piston of an internal combustion engine for improvement in weight and cost reduction. The piston was modelled using Autodesk Inventor 2017 software. The modelled piston was then imported into Ansys for further analysis. Static structural and thermal analysis were carried out on the pistons of the four different materials namely: Al 413 alloy, Al 384 alloy, Al 390 alloy and Al332 alloy to determine the total deformation, equivalent Von Mises stress, maximum shear stress, and the safety factor. The results of the study revealed that, aluminium 332 alloy piston deformed less compared to the deformations of aluminium 390 alloy piston, aluminium 384 alloy piston and aluminium 413 alloy piston. The induced Von Mises stresses in the pistons of the four different materials were found to be far lower than the yield strengths of all the materials. Hence, all the selected materials including the implementing material have equal properties to withstand the maximum gas load. All the selected materials were observed to have high thermal conductivity enough to be able to withstand the operating temperature in the engine cylinders.展开更多
The paper presents the results of a thermo-mechanical analysis of the rolling two stepped shafts.One of the shafts has a toothed step with skew teeth,while the other has a worm winding in the shape of a trapezoidal sc...The paper presents the results of a thermo-mechanical analysis of the rolling two stepped shafts.One of the shafts has a toothed step with skew teeth,while the other has a worm winding in the shape of a trapezoidal screw.The shape of the rolling tools resembles that of the tools used in the Roto-Flo rolling method;yet unlike in Roto-Flo,the shafts are hot-rolled and no centres are used to stabilize the position of the workpiece during the forming process.For the calculations made with use of the DEFORM-3D process simulation system it has been assumed that the rolled shafts are made from 2618 aluminium alloy.As a result of the calculations made,it has been found that the toothed stepped shafts can be formed in one pass by means of the cross rolling process.Additionally,the temperature and strain distribution in the rolled product have been determined as well as some data concerning the forces which are necessary for the rolling process have been obtained.展开更多
The brazing of diamond is a promising way to fabricate grinding wheels for efficient machining and precision grinding.This work investigated the feasibility of bonding diamond grits onto Aluminium Alloy 7075(AA7075)su...The brazing of diamond is a promising way to fabricate grinding wheels for efficient machining and precision grinding.This work investigated the feasibility of bonding diamond grits onto Aluminium Alloy 7075(AA7075)substrate with a Ag–Cu–Ti filler alloy via laser fusion brazing.The interfacial microstructures and the strength of the brazed diamond joints were studied.The cross-section of the brazed diamond joint consists of a molten filler alloy layer,a molten pool,a heat effect zone,a columnar crystal zone and an equiaxed crystal zone.Within the interface of the filler alloy/substrate metal,microstructures observed possibly were Ag(s.s),Al(s.s),Tix Al,Al2 Cu and Mg intermetallic compounds.A layer of Ti C with a thickness of about 30–50 nm was found at the bonding interface of the diamond/filler alloy.The averaged peak shear force of the brazed joints was found to be approximately 39.8 N.The abrasion grinding test indicated that the diamond/AA7075 brazed joint was adequate for grinding.However,the pulled-off of grit was found to be the primary failure of this type of brazed joint.This work broadened the brazing diamond technique and the range of applications of brazed diamond wheels for efficient grinding.展开更多
7 xxx welding wire was self-made by spray forming ingots drawn to series welding wires products,and then TIG butt welding test is used for 5 mm thick 7075 high-strength aluminium alloy.After welding,the stress relief+...7 xxx welding wire was self-made by spray forming ingots drawn to series welding wires products,and then TIG butt welding test is used for 5 mm thick 7075 high-strength aluminium alloy.After welding,the stress relief+solid-solution aging heat treatment(T6)were performed to joints,and the mechanical properties and microstructure of the joints before and after heat treatment were comparative analyzed.The results show that the properties of the heat-affected zone(HAZ)of the joint before heat treatment decreas,and the joint is softened.The welded joints tensile strength is 271.8 MPa,the elongation is 5.6%,and the average hardness of the weld is 118.4 HV.The second phase particles such asη(Mg Zn2),S(Al2 Cu Mg),Al13 Fe4 are distributed in a network layer,with no apparent element segregation.After heat treatment,the structure of each area of the joint is coarsened,and a small amount of Fe-containing impurity phases are distributed.Theηand S phases are dissolved in the matrix.The hardness of each area of the joint is increased to 155 HV,and the softening zone is disappeared,this leads the joint elongation close to 16.9%.The tensile strength is increased to 511.8 MPa,reaching 94%of the base metal tensile strength.展开更多
This paper studies the effect of Ce on the thermal stability of the Ω phase in an Al-Cu-Mg-Ag alloy by TEM and tensile testing. It has been shown that Ce substantially increases the nucleation density of the Ω phase...This paper studies the effect of Ce on the thermal stability of the Ω phase in an Al-Cu-Mg-Ag alloy by TEM and tensile testing. It has been shown that Ce substantially increases the nucleation density of the Ω phase by acting as the heterogeneous nucleation center. Most impor-tantly,Ce improves the thermal stability of the Ω phase by decreasing the diffusion velocity of Cu atoms and increasing the energy barrier of the thickening ledge nucleation,thus improving the strength of the Al-Cu-Mg-Ag alloy at both room-and elevated-temperatures.展开更多
In view of their excellent mechanical properties, workability and heat treatment characteristics, MDN 138 & MDN 250 have been widely used in missile, rocket and aerospace industries. With light weight and high per...In view of their excellent mechanical properties, workability and heat treatment characteristics, MDN 138 & MDN 250 have been widely used in missile, rocket and aerospace industries. With light weight and high performance characteristics HE 20 aluminium alloy acts as an important material in defence and aerospace applications. The galvanic corrosion behaviour of the metal combinations HE 20 / MDN 138 and HE 20 / MDN 250, with 1:1 area ratio, has been studied in natural seawater using the open well facility of CECRI's Offshore Platform at Tuticorin for a year. The open circuit potentials of MDN 138, MDN 250 and HE 20 of the individual metal, the mixed potential and galvanic current of the couples HE 20 / MDN 138 and HE 20 / MDN 250 were periodically monitored throughout the study period. The calcareous deposits on MDN 138 and MDN 250 were analysed using XRD. The results of the study reveal that that HE 20 has offered required amount of protection to MDN 138 & MDN 250.展开更多
Electromagnetic forming is a high-speed forming technology by which hollow profiles can be compressed or expanded. It is done with a pulsed magnetic field to apply Lorentz’ forces at electrically conductive material....Electromagnetic forming is a high-speed forming technology by which hollow profiles can be compressed or expanded. It is done with a pulsed magnetic field to apply Lorentz’ forces at electrically conductive material. Electromagnetic hollow tube expansion is limited by the fragmentation tendency. This work attempts to use a combination of analytical and computational approach to compute the net tangential stress during tube expansion. A simplified analytical framework to estimate the temporal evolution of plastic stresses present in aluminium alloy AA5052 at low and high applied magnetic pressures is developed based upon dynamic imaging. The time resolved images captured using current synchronised high speed camera record the overall dimensional changes of the tube that is validated by multi-physics simulation of expansion process. Imaging of hollow tube expansions at two selected peak currents has been carried out at various current levels in the range 76 - 160 kA. The direct visualisation of the increase in the tube diameter at two current levels provided a comparison of the developing net tangential stresses in the hollow tube during the undamaged and fragmented expansion. Imaging of tube expansion also facilitates the estimation of the strain rate experienced by the tube and was in the range of ~1700 s<sup>-1</sup> to ~1200 s<sup>-1</sup>. The propensity of fragmentation was found to be due to the level and duration of generated tangential stresses above the yield stress during expansion of the aluminium tubes. Presented study provides a mean of exploiting the enhanced formability of aluminium alloys using electromagnetic forming.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.
基金Mr.Sameer MD,Research Scholar(Enrolment No.:16407002)under the guidance of Dr.Anil Kumar Birru,As-sistant professor in Department of Mechanical Engineering,NIT Manipur,would also like to acknowledge the cooper-ation of NIT Warangal to carry SEM analysis and Fr.Rev Augustine Reddy Director,CJITS for his support in carrying this research work.
文摘In the present research work,AZ91 magnesium alloy and AA6082-T6 aluminium alloy were joined by friction stir welding process.The comparison of microstructure and mechanical properties between different joints by varying the different materials on advance and retreating sides were mainly studied.Four different welds have been prepared to find the material mixing between the similar and dissimilar joints.The joint interfaces of the welds have been investigated by employing an optical microscope and scanning electron microscope.When Mg was placed on advancing side(AS),more aluminium content was soluble in nugget zone than the case where Mg was placed on the retreating side(RS).Thin intermetallic layer in the joint interface of Mg/Al and thick intermetallic layer with poor adhesion of the aluminium and magnesium have been observed in the dissimilar joints varying the sides.The highest UTS of 172.3 MPa was found for Mg-Al when Mg was placed on AS and lower UTS of 156.25 MPa was obtained when Mg was placed on RS.Hardness of 86 Hv and 89 Hv were observed in the Stir zone for the dissimilar AZ91 Mg alloy and AA6082-T6 Al alloy when AZ91Mg alloy was placed on the AS and on the RS respectively.Fractography was also carried out to find the mode of failure.
基金Supported by the National Natural Science Foundation of China(No 59201010)Hubei Province Natural Science Foundsation。
文摘The superplastic deformation of aluminium alloy 7475 applied electric current pulse has been studied.The results presented that applying a high density current pulse raises both the elongation rate and the m value,and makes supperior superplastic properties at high strain rate of 10^(-2)s^(-1),the optimum deformation temperature could move from 530℃to 480~510℃,TEM observation showed the superplastic deformation of the alloy is the results of grain boundary slips and dislocation slips in grains under function of the electron wind;the intergranular tear is a main behavior of fracture of the alloy.
文摘Rapidly solidified 2024 aluminium alloy powders were mechanically milled, then consolidated to bulk form. The microstructural changes of the powders in mechanical milling (MM) and consolidation process were characterized by X-ray diffraction analyses and transmission electron microscopy observations. The results showed that mechanical milling reduced the grain size to nanometer, dissolved the Al2Cu intermetallic compound into the aluminium matrix and produced an aluminium supersaturated solid solution. During consolidation process. the grain size increased to submicrometer, and the Al2Cu and Al2(Cu, Mg, Si, Fe, Mn) compounds precipitated owing to heating. Increasing consolidation temperature and time results in obvious grain growth and coarsening of second phase particles. The tensile yield strength of the consolidated alloy with submicrometer size grains increases with decreasing grain size, and it follows the famous HallPetch
基金Partially Funded by National Research Universities(NRU)(ENG 5805855)Faculty of Engineering,Prince of Songkla University,Hatyai Songkhla,Thailand
文摘7XXX series aluminium alloys generally present low weldability by fusion welding methods because of the sensitivity to weld solidification cracking, vaporization of strengthening alloys and other defects in the fusion zone. Friction stir welding(FSW) can be deployed successfully with aluminium alloys. We presented the effect of post-weld heat treatment(PWHT) on the microstructure and mechanical properties of SSM7075 joints. Semi solid plates were butt-welded by FSW at a rotation speed of 1110 r/min, welding speeds of 70 and 110 mm/min. Solution treatment, artificial aging, and T6(solution treatment and artificial aging combined) were applied to the welded joints, each with three samples. It was found that the T6 joints at the speed of 70 mm/min yielded the highest tensile strength of 459.23 MPa. This condition best enhanced the mechanical properties of FSW SSM7075 aluminium alloy joints.
基金Financial assistance from Armament research board,New Delhi,India
文摘High strength-to-weight ratio of non-ferrous alloys, such as aluminium, magnesium and titanium alloys, are considered to be possible replacement of widely accepted steels in transportation and automobile sectors. Among these alloys, magnesium is self explosive and titanium is costlier, and aluminium is most likely to replace steels. Application of aluminium or its alloys is also thought of as an appropriate replacement in defence field, especially to enhance the easiness in mobility of combat vehicles while maintaining the same standard as that of conventional armour grade steels. Hence most of the investigations have been confined to aluminium or its alloys as base material and open an era of developing the newer composite materials to address the major limitation, i.e. tribological properties. The surface composites can be fabricated by incorporating the ceramic carbides like silicon carbide, carbides of transition metals and oxides of aluminium using surface modification techniques, such as high energy laser melt treatment, high energy electron beam irradiation and thermal spray process which are based on fusion route. These techniques yield the fusion related problems, such as interfacial reaction, pin holes, shrinkage cavities or voids and other casting related defects, and pave the way to need of an efficient technique which must be based on solid state. Recently developed friction stir processing technique was used in the present investigation for surface modification of AA7075 aluminum alloy, which is an alternative to steels. In the present investigation, 160 μm sized boron carbide powder was procured and was reduced to 60 μm and 30 μm using high energy ball mill. Subsequently these powders were used to fabricate the surface composites using friction stir processing.Ballistic performance testing as per the military standard(JIS.0108.01) was carried out. In the present work, an analytical method of predicting the ballistic behavior of surface composites was developed. This method was based on energy balance, i.e., the initial energy of impact is same as that of energy absorbed by multi layers. An attempt also has been made to validate the analytical results with the experimental findings. Variation between the analytical and experimental results may be accounted due to the assumptions considering such as isotropic behavior of target and shearing area of contact as cylindrical instead of conical interface As the analytical model yields the ballistic performance in the closer proximity of experimentally obtained, it can be considered to be an approximation to evaluate the ballistic performance of targets.
基金Sponsored by the National Science and Technology Major Project(Grant No.2014ZX04001011)
文摘Residual stress is one of the factors affecting the machining deformation of monolithic structure parts in the aviation industry. Thus,the studies on machining deformation rules induced by residual stresses largely depend on correctly and efficiently measuring the residual stresses of workpieces. A modified layer-removal method is proposed to measure residual stress by analysing the characteristics of a traditional layer-removal method. The coefficients of strain release are then deduced according to the simulation results using the finite element method( FEM). Moreover,the residual stress in a 7075T651 aluminium alloy plate is measured using the proposed method,and the results are then analyzed and compared with the data obtained by the traditional methods. The analysis indicates that the modified layer-removal method is effective and practical for measuring the residual stress distribution in pre-stretched aluminium alloy plates.
文摘Commercial aluminium alloy sheets are presently sem ic ontinuously, direct chill casting billets that are hot and cold rolled to the fi nal gauge. Interest has been shown in continuous methods which eliminate the ho t rolling step through rapid solidification of the molten metal to the final sla b. Accordingly, sheets are produced by homogenization, cold rolling, intermedia te and final annealing of these roll-cast slabs. The problem of earing is of gr eat concern as it causes frequent interruption of production runs and leads to m aterial wastage. Therefore, it is quite desirable that earing can be predic ted and consequently necessary measures be taken to minimize or eliminate this u nwanted phenomenon. It is accepted generally that, the principal source of earing is the crystallogr aphic anisotropy arising from non-random distribution of crystal orientations i n the material. Accordingly, several attempts have been made to correlate the m echanical and crystallographic properties of the materials to the earing behavio ur for predictive purposes. Some of these are based on continuum concepts which concentrate on the macroscopic rather than the microscopic aspects of the mater ials. To accommodate the microstructural features of the material, some models have been developed. A more recent approach which provides a connection between texture and plastic anisotropy parameters of the material is the Continuum Mech anics of Textured Polycrystals (CMTP) method proposed by Lin et al. A simplifie d version of this method has been suggested by Chan with promising accuracy for aluminium and copper sheets. AA3105 and AA8011 aluminium alloy sheets were used in this investigation. The a s-cast slabs were cold rolled to the final thickness of 1.0 mm. Different anne aling temperatures in the range of 420 ℃ to 540 ℃ produced a range of R-value s. Circular blanks of 60 mm diameter were machined and deep drawn using a cylind rical flat-bottom punch of 33 mm diameter. The heights of the drawn cups were measured at 0, 45 and 90° to the rolling direction, with the aid of a microme ter accurate to 10 -2 mm. The earing percentage was then calculated usin g the following formula: % earing=h p-h v1/2(h p+h v)(1) where h p is the distance between the bottom of the cup and the peak of ear , and h v is the distance between the bottom of the cup and the valley of t he ear. For the measurement of plastic strain ratios (R-values), tensile specimens cut at 0, 45 and 90° to the rolling direction were photogridded with 1mm square s. These specimens were then stretched in the range of uniform deformation and the dimensional changes were measured with the aid of a travelling microscope. The strain ratios, whether R 0, R 45 or R 90 were determined from the following equation: R θ=dε wdε t=dε wdε l+dε w(2) where Θ refers to the specimen orientation and dε w and dεl refer to the transverse and longitudinal strains of the gauge section, respectively. The av erage strain ratio, R, and the parameter ΔR were then calculated from: R=14(R 0+2R 45+R 90)(3) ΔR=12(R 0-2R 45+R 90)(4) where R 0, R 45 and R 90 values are determined using specimen s cut at 0, 45 and 90° to the rolling direction, respectively. Finally, a continuum mechanics approach using different yield criteria is employ ed for the prediction of earing behaviour under different conditions of the mate rials. Instead of using texture data, the yield stress values are obtained by d ifferent anisotropic yield criteria such as; Hosford, Hill, and Zhou. The predicted earing profiles are compared to the experimental data and the suit ability of different yield criteria is discussed.
文摘In this study, it is aimed to investigate effect of the grain refinement on the mechanical properties of the AA 6082. The micro structure which plays crucial role in determining the mechanical properties of the alloys is varied according to grain size, chemical composition and cooling rate. The prescription was prepared by determining the chemical composition range according to the standard (TSE-EN-573). The casting experiments were performed on the 6082 aluminium alloy which belongs to Al-Mg-Si system with different percentages of grain refinement (AlTi<sub>5</sub>B<sub>1</sub>) and chemical composition. Heat treatment that is homogenization and artificial aging was applied after casting and extrusion process, respectively. The microstructure analysis and mechanical tests were done on the produced samples in order to understand the structural and mechanical strength of the material. The experimental results showed that using the grain refinements is contributed to increasing the mechanical properties. It was observed that the mechanical strength values increased by 17% after the reduction of the grain size by 69% with the 0.11% addition of the AlTi<sub>5</sub>B<sub>1</sub> master alloy.
基金the financial support by the National Natural Science Foundation of China(11502044,U1906233,and 52175289)the Fundamental Research Funds for the Central Universities(DUT17RC(3)104)the National Key R&D Program of China(2018YFA0703 and 2019YFA0708804).
文摘Broad use of lightweight aluminium alloy parts in automobile manufacturing,aerospace,electronic communication,and rail transit is mainly formed through deep drawing process.Deep drawing friction is a key boundary condition for controlling the forming quality of aluminium alloy parts.However,due to the oxidation and adhesion tendency of aluminium alloys,the tribological situations of aluminium alloy deep drawing(AADD)system is more complicated than those of traditional deep drawing of steel sheets.Therefore,the study of AADD friction is essential for manufacturing high-performance aluminium alloy parts.Herein,aiming to provide a valuable reference for researchers in related fields,a comprehensive review of AADD friction is provided,including friction mechanism,influencing factors,friction measurement,friction model,friction simulation,and lubrication-free friction control.Finally,a brief conclusion and several current challenges were discussed.
基金co-supported by the National Natural Science Foundation of China(No.52005020)Guangdong Basic and Applied Basic Research Foundation(No.2019A1515110851).
文摘In the aerospace industry,integrated aluminium alloy plates and stiffened panels with high accuracy and performance attract significant interest.To manufacture these panels as integrity with high accuracy,multiple processes need to be utilised,such as machining,welding and forming.During the whole manufacturing chain,residual stresses can be generated and redistributed in the components among different processes.The residual stress would significantly affect the shapes and properties of the final products.Currently,these great effects are not well considered in the design and manufacturing processes.This paper aims to draw a general understanding of the residual stress generated in the pre-manufacturing processes and its effects on subsequent manufacturing processes.The mechanisms and distributions of residual stresses generated in typical premanufacturing processes of structural panels,including machining,welding and additive manufacturing(AM),are firstly summarised.The detailed effects of generated residual stresses on distortion and application properties in subsequent manufacturing processes are then concluded.In addition,current methods developed for the investigation of residual stress effect in multi-processes manufacturing are critically reviewed,including experimental,analytical,finite element(FE)and machine learning methods.Furthermore,the future development trend of methods for residual stress consideration and control in the design of manufacturing processes is summarised,providing comprehensive guidance to achieve the high accurate manufacturing of aluminium alloy structural components.
基金supported by the Nation Natural Science Foun-dation of China(No.51874127)Postgraduate Scientific Re-search Innovation Project of Hunan Province(No.CX20210403).
文摘The quenching-induced residual stress in ultrahigh strength Al-Zn-Mg-Cu alloys has a great influence on their precipitation behaviour in subsequent heat treatment and the properties of the final products.In the present work,the cladding quenching method was employed for 7085 Al alloy slabs to tailor different quenching residual stresses.Then the effects of quenching residual stress on the precipitation behaviour of the 7085 Al alloy were investigated through finite element analysis,residual stress and hardness distri-bution measurements and microstructural examinations.The results indicate that the reduction in resid-ual stress increases with increasing cladding layer thickness.For a cladding layer thickness in the range of 1-1.4 mm,the residual stress is almost eliminated.The hardness at the surface of the aged sample with a large compressive residual stress is decreased,while the hardness at the centre of the sample with a large tensile residual stress is increased.The hardness is approximately identical between the aged sam-ples with little or no residual stress.The elastic lattice distortion caused by residual stress is found to promote the nucleation of precipitates during the artificial ageing process.The in-depth mechanisms for the effect of quenching residual stress on the precipitation of 7085 Al alloy are also discussed.
文摘The main objective of this research was to examine the suitability of aluminium alloy to design a piston of an internal combustion engine for improvement in weight and cost reduction. The piston was modelled using Autodesk Inventor 2017 software. The modelled piston was then imported into Ansys for further analysis. Static structural and thermal analysis were carried out on the pistons of the four different materials namely: Al 413 alloy, Al 384 alloy, Al 390 alloy and Al332 alloy to determine the total deformation, equivalent Von Mises stress, maximum shear stress, and the safety factor. The results of the study revealed that, aluminium 332 alloy piston deformed less compared to the deformations of aluminium 390 alloy piston, aluminium 384 alloy piston and aluminium 413 alloy piston. The induced Von Mises stresses in the pistons of the four different materials were found to be far lower than the yield strengths of all the materials. Hence, all the selected materials including the implementing material have equal properties to withstand the maximum gas load. All the selected materials were observed to have high thermal conductivity enough to be able to withstand the operating temperature in the engine cylinders.
基金the Structural Funds under the Innovative Economy Operational Programme (IE OP)financed from the European Regional Development Fund (No.POIG.0101.02-00-015/08)
文摘The paper presents the results of a thermo-mechanical analysis of the rolling two stepped shafts.One of the shafts has a toothed step with skew teeth,while the other has a worm winding in the shape of a trapezoidal screw.The shape of the rolling tools resembles that of the tools used in the Roto-Flo rolling method;yet unlike in Roto-Flo,the shafts are hot-rolled and no centres are used to stabilize the position of the workpiece during the forming process.For the calculations made with use of the DEFORM-3D process simulation system it has been assumed that the rolled shafts are made from 2618 aluminium alloy.As a result of the calculations made,it has been found that the toothed stepped shafts can be formed in one pass by means of the cross rolling process.Additionally,the temperature and strain distribution in the rolled product have been determined as well as some data concerning the forces which are necessary for the rolling process have been obtained.
基金National Natural Science Foundation of China(Nos.51975221,U1805251 and 51575198)。
文摘The brazing of diamond is a promising way to fabricate grinding wheels for efficient machining and precision grinding.This work investigated the feasibility of bonding diamond grits onto Aluminium Alloy 7075(AA7075)substrate with a Ag–Cu–Ti filler alloy via laser fusion brazing.The interfacial microstructures and the strength of the brazed diamond joints were studied.The cross-section of the brazed diamond joint consists of a molten filler alloy layer,a molten pool,a heat effect zone,a columnar crystal zone and an equiaxed crystal zone.Within the interface of the filler alloy/substrate metal,microstructures observed possibly were Ag(s.s),Al(s.s),Tix Al,Al2 Cu and Mg intermetallic compounds.A layer of Ti C with a thickness of about 30–50 nm was found at the bonding interface of the diamond/filler alloy.The averaged peak shear force of the brazed joints was found to be approximately 39.8 N.The abrasion grinding test indicated that the diamond/AA7075 brazed joint was adequate for grinding.However,the pulled-off of grit was found to be the primary failure of this type of brazed joint.This work broadened the brazing diamond technique and the range of applications of brazed diamond wheels for efficient grinding.
文摘7 xxx welding wire was self-made by spray forming ingots drawn to series welding wires products,and then TIG butt welding test is used for 5 mm thick 7075 high-strength aluminium alloy.After welding,the stress relief+solid-solution aging heat treatment(T6)were performed to joints,and the mechanical properties and microstructure of the joints before and after heat treatment were comparative analyzed.The results show that the properties of the heat-affected zone(HAZ)of the joint before heat treatment decreas,and the joint is softened.The welded joints tensile strength is 271.8 MPa,the elongation is 5.6%,and the average hardness of the weld is 118.4 HV.The second phase particles such asη(Mg Zn2),S(Al2 Cu Mg),Al13 Fe4 are distributed in a network layer,with no apparent element segregation.After heat treatment,the structure of each area of the joint is coarsened,and a small amount of Fe-containing impurity phases are distributed.Theηand S phases are dissolved in the matrix.The hardness of each area of the joint is increased to 155 HV,and the softening zone is disappeared,this leads the joint elongation close to 16.9%.The tensile strength is increased to 511.8 MPa,reaching 94%of the base metal tensile strength.
基金the Natural Science Foundation of Hunan Province (No. 07JJ3117)the Chinese Postdoctoral Science Foundation (No. 20070410303)the High Technology Research and Development Program of Hunan Province, China (No. 06FJ2007).
文摘This paper studies the effect of Ce on the thermal stability of the Ω phase in an Al-Cu-Mg-Ag alloy by TEM and tensile testing. It has been shown that Ce substantially increases the nucleation density of the Ω phase by acting as the heterogeneous nucleation center. Most impor-tantly,Ce improves the thermal stability of the Ω phase by decreasing the diffusion velocity of Cu atoms and increasing the energy barrier of the thickening ledge nucleation,thus improving the strength of the Al-Cu-Mg-Ag alloy at both room-and elevated-temperatures.
基金the Project Director, DRDL, Hyderabad for the financial support (Project No. SSP0709)
文摘In view of their excellent mechanical properties, workability and heat treatment characteristics, MDN 138 & MDN 250 have been widely used in missile, rocket and aerospace industries. With light weight and high performance characteristics HE 20 aluminium alloy acts as an important material in defence and aerospace applications. The galvanic corrosion behaviour of the metal combinations HE 20 / MDN 138 and HE 20 / MDN 250, with 1:1 area ratio, has been studied in natural seawater using the open well facility of CECRI's Offshore Platform at Tuticorin for a year. The open circuit potentials of MDN 138, MDN 250 and HE 20 of the individual metal, the mixed potential and galvanic current of the couples HE 20 / MDN 138 and HE 20 / MDN 250 were periodically monitored throughout the study period. The calcareous deposits on MDN 138 and MDN 250 were analysed using XRD. The results of the study reveal that that HE 20 has offered required amount of protection to MDN 138 & MDN 250.
文摘Electromagnetic forming is a high-speed forming technology by which hollow profiles can be compressed or expanded. It is done with a pulsed magnetic field to apply Lorentz’ forces at electrically conductive material. Electromagnetic hollow tube expansion is limited by the fragmentation tendency. This work attempts to use a combination of analytical and computational approach to compute the net tangential stress during tube expansion. A simplified analytical framework to estimate the temporal evolution of plastic stresses present in aluminium alloy AA5052 at low and high applied magnetic pressures is developed based upon dynamic imaging. The time resolved images captured using current synchronised high speed camera record the overall dimensional changes of the tube that is validated by multi-physics simulation of expansion process. Imaging of hollow tube expansions at two selected peak currents has been carried out at various current levels in the range 76 - 160 kA. The direct visualisation of the increase in the tube diameter at two current levels provided a comparison of the developing net tangential stresses in the hollow tube during the undamaged and fragmented expansion. Imaging of tube expansion also facilitates the estimation of the strain rate experienced by the tube and was in the range of ~1700 s<sup>-1</sup> to ~1200 s<sup>-1</sup>. The propensity of fragmentation was found to be due to the level and duration of generated tangential stresses above the yield stress during expansion of the aluminium tubes. Presented study provides a mean of exploiting the enhanced formability of aluminium alloys using electromagnetic forming.
