| Magnesium alloy is the lowest density metal structural material at present,and its mechanical properties are comparable to those of commercial aluminum alloy.As an automobile parts material,it produces lower fuel consumption than traditional steel and aluminum parts,which makes the application and development potential of magnesium alloy in lightweight engineering attract extensive attention.Therefore,in automobile and other manufacturing fields,the demand for magnesium alloy sheet is increasing year by year,and it is the future trend to develop magnesium alloy sheet with higher formability.A large number of studies have confirmed that High Strain Rate Rolling（HSRR）,as a new type of large plastic deformation process in recent years,is suitable for preparing magnesium alloy sheets with excellent properties.In order to explore whether the properties of HSRR sheet can be further improved after heat treatment,the rolled sheet at370℃/6.93 s-1is used as the initial material,and the sheet after deformation of HSRR magnesium alloy is annealed,so as to clarify the influence law of heat treatment process parameters on the changes of its microstructure and mechanical properties and seek the optimal match between microstructure and properties.In this paper,the evolution of HSRR plate during heat treatment and the influence of heat treatment parameters on microstructure were studied by selecting four groups of annealing temperatures of 160℃,220℃,280℃and 340℃respectively,and then holding for 15 min,30 min,45 min and 60min.The results show that recrystallization preferentially nucleates in the shear zone,twin-like lamellar structure and other deformed areas in HSRR during annealing treatment,and the second phase also preferentially precipitates in the position with higher energy and larger deformation.According to the results of annealing treatment,the static recrystallization dynamic equation and microstructure evolution model are established.In addition,it is clarified that HSRR plate has a strong temperature effect during annealing,and the annealing temperature has a greater influence on its structure than the holding time.By testing the tensile properties of annealed sheet of HSRR deformed AM60B magnesium alloy at room temperature,the variation law of tensile properties with annealing parameters and the fracture mechanism of sheet with different microstructure were revealed.The results show that with the increase of annealing temperature,the elongation of the plate is improved,while with the extension of holding time,the tensile strength and yield strength of the plate fluctuate to some extent,showing that they first decrease and then slowly increase,and the performance of the plate is the best when it is annealed at 340℃-15 min.The tensile properties of HSRR magnesium alloy sheet annealed at 340℃-30 min were tested,and the true stress-strain curve was obtained.The tensile constitutive equation of HSRR magnesium alloy at high temperature was established,and the deformation activation energy Q was 138.38k J/mol,which revealed that the main coordinated deformation mechanism of annealed sheet was lattice diffusion under the deformation parameters studied in this paper. |
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