Research On The Superplasticity And Electrical Conductivity Of Aluminum Alloy

Aluminum and aluminum alloy material have a series of excellent properties.They are widely used in aerospace,transportation,construction and decoration,containers,machine and electrical appliances,electronic communications,petrochemical industry,energy and other industries.And they have become the important basis material for the development of national economy.Along with the rapid development of science and technology,the requirements of superplasticity,conductivity,etc.of aluminum alloy have put forward higher requirements on material performance.Usually,people improve the performance of aluminum alloy through alloying,plastic deformation and so onAluminum alloys were produced by castex and ECAP-Conform technology in this thesis.On the one hand,the analysis focused on the characteristics of high-temperature superplastic deformation of Al-1.88Mg-0.18Sc-0.084Er alloy through the hot compression deformation under different deformation conditions.The evolutions of grain structures and cavities,fracture modes,microstructures such as precipitated phases,dislocations,and subgrains were studied by means of OM,SEM,XRD,TEM,and EBSD.Based on the true stress-true strain curves and DRX microstructures,constitutive equation and processing maps of hot deformation and DRX model were obtained and the constitutive model describing the superplastic deformation mechanism was established to elucidate the superplastic deformation mechanism of the present alloy.And then,the high-temperature superplasticity of the present alloy was studied again by tensile testing at elevated temperature.On the other hand,the micro structure,electrical conductivity and mechanical properties of alloy at room temperature was researched through the solid solution treatment,drawing and aging process to preparation of high conductivity and high strength aluminum alloy wire.The main researches and conclusions are summarized as following:(1)Aluminum alloy wire was produced by castex and ECAP-Conform technology.The alloy has a fine grain size and the structure is homogeneous.And then the superplasticity of the alloy was studied by hot compression experiments.The experimental results indicate that the flow stress and peak stress corresponding to strain decrease with increasing deformation temperature and decreasing strain rate during the hot compression tests.At the same time,dynamic recrystallization behavior proceeds more and more fully.The best hot deformation temperature of 793K and strain rate of 10-3s-1?10-2s-1 for the alloy was obtained by calculation and analysis of the m and deformation condition.Constitutive equation of the alloy was established by calculation.At the same time,processing maps of the alloy were drawn based on the Dynamic Material Modeling(DDM).There are two instability regimes and one peak value domain where the efficiency of power dissipation reaches a local maximum.These processing maps can accurately forecast the feasibility of hot deformation for the alloy by comparing with the actual microstructure.(2)Obvious dynamic recrystallization behavior was observed in hot deformation for the Al-1.88Mg-0.18Sc-0.084Er alloy according to microstructure and true stress-true strain curves.Dynamic recrystallization model were obtained to describe the influences of deformations on dynamic recrystallization.The constitutive model describing the superplastic deformation mechanism was built by calculating the values of stress exponent,grain size exponent,deformation activation energy to investigate the superplastic deformation mechanism of the alloy.The superplastic performance of the alloy was further observed by the high temperature tensile test and the maximum elongation to failure of 202%was demonstrated at 723K and the initial strain rate of 1×10-4s-1.(3)The effects of rare earth elements(La,Ce,Y,Sc,Er)and processing methods(castex,ECAP-Conform,solid solution,drawing,artificial aging)on microstructure and properties of Al-Mg-Si alloy were discovered.Eventually,it was found that Ce can increase electrical conductivity most and it is reached 53.5%?55.2%IACS.The tensile strength were similar and it was between 255 and 295MPa.