| With the advantages of high strength,good forming property,corrosion resistance and excellent welding performance,6N01 aluminium alloy(AA6N01)is widely applied in the production of high-speed trains.At present,with the rapid development of high-speed train technology at home,the requirements for the performance and quality of car body profiles have become increasingly stringent.The microstructure defects,such as uneven grain size,coarse-grained layer,overheating or over-burn are still the most important factors affecting the properties and finished rate of aluminum alloy profiles.Therefore,it is very urgent to study the mechanism of the microstructure evolution and to further establish an effective model for predicting the microstructure during hot deformation process of aluminum alloys,which could provide important theoretical support for improving the quality of AA6N01 profiles.In this study,the AA6N01 is chosen to investigate the evolution of microstructure during hot compression and hot extrusion process with the help of metallography(OM),electron backscatter diffraction(EBSD),scanning electron microscope(SEM)and other characterization technologies.The main works of this paper are as follows:(1)The mechanics and thermo-physical parameters of AA6N01 are examined experimentally.The strain and stress date of AA6N01 under different strain rates and temperatures are obtained based on hot compression tests.A physically-based KME constitution equation is established through linear regression to describe the flow behavior of AA6N01 and its material parameters are obtained by inverse analysis method.(2)The specimens of hot compression tests under different experimental conditions are examined through OM and electron backscattered diffraction EBSD.The type of dynamic recrystallization(DRX)during hot compression tests is determined through EBSD analysis.The relationship between the static recrystallization and annealing time is investigated based on metallographic observation.(3)With the self-designed experimental device,a series of extrusion experiments are carried out to investigate the influence of extrusion parameters on microstructure,texture,abnormal grain growth and second-phase particles of AA6N01 during hot extrusion.(4)The microstructure evolution of AA6N01 during hot deformation is investigated through mathematical modeling.DRX kinetic model,DRX grain size model and deformed grain size model are successively built and integrated to describe grain size evolution during hot compression and extrusion process of AA6N01. |
