| As the lightest metal material of structure, magnesium alloys have broad application prospects. The study on wrought magnesium alloy sheet with high performance is prevalent in material research field. Due to the hcp crystal structure and anisotropy caused by basal texture, magnesium alloy sheet has poor plastic processing performance. Refining grains by sever plastic deformation is an effective method to improve the plastic deforming properties of polycrystalline metal materials. Constrained Groove Pressing (CGP) is a kind of preponderant processing technology for improving plastic deformation performance of large sheet. The current research of CGP is concentrated on the metals with preferably plastic formability in room temperature. There is few research on CGP of metals with poor plasticity in room temperature such as magnesium. So the systematic study of CGP magnesium alloy is significant on theory and practice.In this paper, AZ31 magnesium alloy is the researching object of CGP process. The CGP characteristics of AZ31 magnesium alloy sheet are studied through finite element modeling based on DEFORM. Detailed analysis of the flow laws and strain fields of the deformation process are implemented. And the effects of CGP passes, tilt angle and width of die tooth and other parameters on the magnesium alloy processed by CGP are researched as well. The analysis of CGP deformation load features and its guidance for mold design are well studied.With the theoretical analysis, the experimental mold for CGP of AZ31 magnesium alloy at high temperature is designed, and related experiments research is conducted. Through metallographic observation and XRD testing, the evolution of grain structure and crystal orientation in the CGP deformation process is deeply revealed. The heat tensile properties of CGP sheet is studied with heat tensile test. The influence rules of deformation temperature, strain rate and pressing measure in experimental process on the microstructure and mechanical properties of magnesium alloys is studied. After CGP process on magnesium alloy sheet, ultra-fine grain is successfully obtained.The annealing process of CGP magnesium alloy sheet is conducted a preliminary study, mainly in the influence of annealing temperature on the sheet with different CGP passes. The evolution of microstructure and crystal orientation and the internal mechanism in annealing process are discussed. The influence rule of annealing on the mechanical properties of CGP sheet deformation is studied, and detailed analysis of the internal relations between mechanical properties and microstructure evolution is implemented. The effects of process parameters and the morphology on deformation mechanism in the heat tensile process are revealed. |
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