Research On Microstructure And Properties Of AM60B Magnesium Alloy Under Plane Compression

Magnesium alloys have been widely used in the fields of aerospace and automotive due to their low density,high shock absorption,and good recyclability.With the increasing demand for magnesium alloy sheets in various fields,it is urgent to develop new preparation technologies for magnesium alloy sheets with excellent performance.The dense hexagonal crystal structure of magnesium alloys leads to their poor plastic forming ability.The traditional plate rolling technology has the disadvantages of high energy consumption and time-consuming in the production of magnesium alloys.High strain rate rolling is an efficient and short process for preparing plates.Fine grained magnesium alloy plates with excellent mechanical properties can be prepared through high strain rate rolling.The initial structure has a significant impact on the processing formability of magnesium alloys.It is of great theoretical significance to study the appropriate heat treatment process and combine it with high strain rate rolling to prepare fine and uniform structures,and to reveal the evolution law of microstructure during the deformation process,providing theoretical and experimental basis for practical applications.In this paper,three different initial microstructures were obtained by homogenizing and solution aging heat treatment of as-cast AM60B magnesium alloy,namely,as-cast microstructure,homogenized microstructure,and solution aging microstructure.The thermal deformation behavior of AM60B alloy with different initial structures was investigated through plane strain compression experiments.Based on Arrhenius equation,a corresponding constitutive model of the material was constructed.The thermal deformation activation energies Q of AM60B alloy in the as-cast,homogenized,and solution aged states were calculated to be 218 k J/mol,115.51 k J/mol,and 173.91 k J/mol,respectively.Using DEFORM-3D finite element analysis software,the plane strain compression process was simulated,and the distribution laws of strain rate field and damage value were analyzed in detail.It was found that the morphological evolution of shear bands was affected by deformation and friction conditions.The simulation results show that the shear band region is prone to deformation defects.The distribution and morphology of shear bands were analyzed,and the formation mechanisms of"X"and"S"shear bands were expounded.By analyzing the deformation microstructure,the microscopic mechanism of shear band formation and dynamic recrystallization nucleation mechanism were revealed,and the effect of the second phase on dynamic recrystallization behavior in the alloy was clarified.The microstructure of the solution aged alloy confirmed that the dynamic recrystallization microstructure of the alloy after plane strain compression deformation evolved most fully.Through hardness testing and data comparison of as cast,homogenized,solution aged alloys,and deformed structures,it was found that there were significant hardness differences between the shear band region and the near shear band region of the as cast,homogenized,and solution aged alloy deformed structures,while the hardness differences between the solution aged alloys were small.Therefore,the solution aged AM60B alloy is more suitable for high strain rate rolling billets,with a dynamic recrystallization structure accounting for78.13%of the deformed microstructure at 310℃and 12.75 s^-1,and an average hardness value of 73 HV.