| AZ31 is a kind of magnesium alloy material with good comprehensive properties.Because of its own advantages,AZ31 has great development potential in lightweight products,energy saving and environmental protection.However,the poor plasticity at room temperature limits its application.In this thesis,the deformation behavior of AZ31 magnesium alloy sheet with different microstructure was studied under various deformation conditions.According to the difference of microstructure,the test materials can be divided into coarse-grained magnesium plate and fine-grained magnesium plate.The tensile test was carried out in the temperature range from room temperature to 300 ?,with the tensile speed of 0.1mm/s,0.5mm/s and 1.0mm/s.The microstructure and fracture morphology were observed by metallographic microscope and scanning electron microscope,and the changes of the macroscopic properties and microstructure of the two kinds of magnesium plates under different conditions were analyzed and compared.On this basis,the coarse-grained magnesium plate was used as the main test material to carry out the round test under different conditions.In the process of tube drawing test,DYNAFORM is used to simulate the drawing process and summarize the appropriate process parameters.Then the drawing performance of two kinds of magnesium plates is compared.The results show that,with the increase of temperature and the decrease of deformation speed,the ductility and the deformation resistance of the two kinds of magnesium plates increase,and they soften under the heating condition,in which the fine grain structure deforms more evenly and is more sensitive to deformation speed.In the temperature range from room temperature to 150 ?,twinning is the main deformation coordination mode for coarse-grained structure,while grain boundary sliding is the main deformation coordination mode for fine-grained structure.Dynamic recrystallization occurs in the magnesium plate with coarse-grained structure at 200 ?,and dynamic recrystallization nucleation has been observed in the magnesium plate with fine-grained structure at 150 ?,the dynamic recrystallization structure of two kinds of magnesium plates in the temperature range of 250 ? ~ 300 ? has replaced the original structure,and the recrystallization grain grows obviously with the increase of temperature and the decrease of speed.The fracture mode of the two kinds of magnesium plates is little different,which is mainly affected by temperature and less affected by deformation speed.The temperature range from room temperature to 200 ? is quasi cleavage fracture,and above 200 ? is dimple aggregation ductile fracture.A set of heating and temperature control system is designed for the drawing test of cylindrical cup.DYNAFORM is used to analyze the thickness change during the drawing process,optimize the blank holder clearance and lubrication condition parameters,and determine that the blank holder clearance of 0.7mm thick magnesium plate is 0.80 mm,and the lubrication condition is graphite lubrication.Through the test,it is found that the influence of temperature on the drawing forming is obvious.The LDR value is less than 1.44 at room temperature.The LDR value can reach 2.15 at 200 ?.At 200 ? and 1.0mm/s drawing speed,75 mm diameter round billet with coarse-grained structure can be successfully drawn to the maximum forming height,when the other conditions are the same,the fine-grained magnesium sheet can be successfully drawn at 175 ?,the formability of fine-grained structure is better than that of coarse-grained structure. |
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