Joining of dissimilar metals will offer many advantages in transportation sectors such as fuel consumption,weightreduction and emission reduction.However,joining of aluminium(Al)alloys with magnesium(Mg)alloys by fusi...Joining of dissimilar metals will offer many advantages in transportation sectors such as fuel consumption,weightreduction and emission reduction.However,joining of aluminium(Al)alloys with magnesium(Mg)alloys by fusion welding processis very complicated.Friction stir welding(FSW)is a feasible method to join these two dissimilar alloys.Mixing these two metalstogether in stir zone(SZ)leads to poor corrosion resistance.In this investigation,an attempt has been made to understand thecorrosion resistance of SZ of FSWed dissimilar joints of AA6061Al alloy and AZ31B Mg alloy.Potentiodynamic polarization testwas conducted by varying chloride ion concentration,pH value of the NaCl solution and exposure time.The corroded surfaces wereanalyzed using optical microscopy,scanning electron microscopy and XRD techniques.Of these three factors investigated,exposuretime is found to be the most significant factor to influence the corrosion behaviour of SZ of friction stir welded dissimilar joints ofAl/Mg alloys.展开更多
Cast Al alloys are widely employed for engine components,structural parts,gear box,chassis,etc.and subjected to mechanical cyclic load during operation.The accurate fatigue life prediction of these alloys is essential...Cast Al alloys are widely employed for engine components,structural parts,gear box,chassis,etc.and subjected to mechanical cyclic load during operation.The accurate fatigue life prediction of these alloys is essential for normal operation as fatigue cracks initiated during operation induce the lubrication oil leak and serious safety hazard.Microstructural heterogeneity,including shrinkage/gaspores and secondary phase particles,is the most detrimental factor that affects fatigue life of cast Al alloys.The approximate fatigue life cycles could be estimated based on the size distribution and locations of shrinkage pores/defects.The relationship between crack population and stress was reported by statistical distributions and the cumulative probability for cast Al alloys fail at a certain stress could be predicted by combination of Paris law and pore size distribution.Pore depth was found to dominate the stress field around the pore on the surface and the maximum stress increases sharply when the pore intercepted with the surface at its top.The microstructure of cast Al alloys usually is composed of primary Al dendrites,eutectic silicon,Fe-rich particles and other intermetallic particles are dependent upon alloy composition and heat treatment.The coalescence of microcracks initiated from the fractured secondary phases was clearly found and can accelerate the initiation and propagation of the fatigue cracks.A link between defect features and the fatigue strength needs to be established through a good understanding of the fatigue damage mechanisms associated with the microstructural features under specific loading conditions.This paper reviews the influences of shrinkage/gaspores and secondary phase particles,formed during casting process,on the fatigue life of Al-Si-Mg cast Al alloys.展开更多
基金Council of Scientific and Industrial Research (CSIR), New Delhi, India, for the financial support to carry out this investigation through sponsored project No. 22(0615)/13/EMR-II dated 26.02.2013
文摘Joining of dissimilar metals will offer many advantages in transportation sectors such as fuel consumption,weightreduction and emission reduction.However,joining of aluminium(Al)alloys with magnesium(Mg)alloys by fusion welding processis very complicated.Friction stir welding(FSW)is a feasible method to join these two dissimilar alloys.Mixing these two metalstogether in stir zone(SZ)leads to poor corrosion resistance.In this investigation,an attempt has been made to understand thecorrosion resistance of SZ of FSWed dissimilar joints of AA6061Al alloy and AZ31B Mg alloy.Potentiodynamic polarization testwas conducted by varying chloride ion concentration,pH value of the NaCl solution and exposure time.The corroded surfaces wereanalyzed using optical microscopy,scanning electron microscopy and XRD techniques.Of these three factors investigated,exposuretime is found to be the most significant factor to influence the corrosion behaviour of SZ of friction stir welded dissimilar joints ofAl/Mg alloys.
基金Projects(11790282,U1534204,11572267,51804202,51705344)supported by the National Natural Science Foundation of ChinaProject(E2019210292)supported by the Natural Science Foundation of Hebei Province,China+6 种基金Project(A2019210204)supported by the National Natural Science Foundation for Distinguished Young Scholars,ChinaProject(KQTD20170810160424889)supported by the Shenzhen Peacock Team Program,ChinaProject(2019DB013)supported by the Key Research Project of Southern Xinjiang,ChinaProject(C201821)supported by the High Level Talent Support Project in Hebei,ChinaProject supported by the Youth Top-notch Talents Supporting Plan of Hebei Province,ChinaProject(MCMS-E-0519G04)supported by the State Key Laboratory of Mechanics and Control of Mechanical Structures,Nanjing University of Aeronautics and Astronautics,ChinaProject(201919)supported by the Open Fund of State Key Laboratory of Metastable Materials Science and Technology,Yanshan University,China。
文摘Cast Al alloys are widely employed for engine components,structural parts,gear box,chassis,etc.and subjected to mechanical cyclic load during operation.The accurate fatigue life prediction of these alloys is essential for normal operation as fatigue cracks initiated during operation induce the lubrication oil leak and serious safety hazard.Microstructural heterogeneity,including shrinkage/gaspores and secondary phase particles,is the most detrimental factor that affects fatigue life of cast Al alloys.The approximate fatigue life cycles could be estimated based on the size distribution and locations of shrinkage pores/defects.The relationship between crack population and stress was reported by statistical distributions and the cumulative probability for cast Al alloys fail at a certain stress could be predicted by combination of Paris law and pore size distribution.Pore depth was found to dominate the stress field around the pore on the surface and the maximum stress increases sharply when the pore intercepted with the surface at its top.The microstructure of cast Al alloys usually is composed of primary Al dendrites,eutectic silicon,Fe-rich particles and other intermetallic particles are dependent upon alloy composition and heat treatment.The coalescence of microcracks initiated from the fractured secondary phases was clearly found and can accelerate the initiation and propagation of the fatigue cracks.A link between defect features and the fatigue strength needs to be established through a good understanding of the fatigue damage mechanisms associated with the microstructural features under specific loading conditions.This paper reviews the influences of shrinkage/gaspores and secondary phase particles,formed during casting process,on the fatigue life of Al-Si-Mg cast Al alloys.
