Effect Of Heat Treatment And Deformation Process On Microstructure And Properties Of Magnesium Allay Wheel

Because the magnesium alloy belongs to the hcp structure,the number of sliding systems available at room temperature is small,and the deformation texture is easy to produce,which is difficult to form at room temperature.These conditions have hindered the application of magnesium alloys.Most cast magnesium alloy wheels often have defects,and forged magnesium alloy wheels undergo plastic deformation,which can improve the uniformity of the structure and improve its comprehensive mechanical properties.Electron backscatter diffraction was used to observe and study the microstructure of AZ80 magnesium alloy under the conditions of as-cast,homogenized,and plastic deformation(different deformation temperature and multi-pass deformation),and analyzed the as-cast,homogenized,and plastic deformation microstructure evolution of AZ80 magnesium alloy.The purpose is to study the plastic deformation mechanism of magnesium alloy from the grain boundary coordination effect,and to explore its influence on the grain boundary coordination from the aspects of grain boundary migration and geometrically necessary dislocation density.The main results are as follows:(1)According to the order of as-cast state,homogenization treatment state and modified state,the average grain size of the sample gradually decreases,and the aspect ratio of the average grain shape increases first and then decreases.As the deformation temperature decreases,the average grain size gradually decreases,and the average grain shape aspect ratio decreases first and then increases.With the increase of the degree of deformation,the average grain size of the isothermal multi-pass deformation gradually decreases,and the aspect ratio of the average grain shape decreases first and then increases.(2)The coordination of grain boundaries is closely related to the grain boundary migration and geometrically necessary dislocations density.With the migration of grain boundaries,in the order of as-cast,homogenized heat treatment,and plastic deformation,the small-angle grain boundaries of the sample gradually increased,hindering the progress ofrecrystallization,and the substructure area gradually decreased,in the process of grain boundary migration,the substructure provides energy for the formation of twins.As the deformation temperature decreases,the low-angle grain boundaries increase,and the substructure region increases first and then decreases.With the increase of the degree of deformation,the low-angle grain boundary gradually decreases in the isothermal multi-pass deformation,and the substructure region shows a trend of increasing first and then decreasing.In the order of as-cast state,homogenized heat treatment state,and plastic deformation state,the geometrically necessary dislocations density of the sample showed a trend of decreasing first and then increasing.As the deformation temperature decreases,the geometrically necessary dislocations density increases gradually.With the increase of the degree of deformation,the geometrically necessary dislocations density showed a trend of decreasing first and then increasing,but the overall degree of change was not large.It shows that the geometrically necessary dislocation density is more sensitive to deformation temperature,but not sensitive to deformation degree.(3)Cylindrical texture mainly exists in the as-cast state.As the deformation temperature decreases,the texture types are cylindrical texture,basal texture,and basal texture.With the increase of the degree of deformation,isothermal multi-pass deformation is followed by the texture type of base surface texture,cylinder texture,and base surface texture.