Study On Thermal Deformation Behavior Of AZ80 Magnesium Alloy Thin Wall Tube Under Compression And Torsion

Compression-torsional deformation of magnesium alloys can provide shear stress through rotation while axial pressure is applied to the sample,which can refine the grain-weakened texture.At present,most of the samples used in the study of compression and torsion are solid bars.Since the deformation speed and strain of the sample are closely related to the radius,the research results can only give the relationship between the average equivalent stress and the average equivalent strain,and cannot accurately measure the compression.The true stress-strain relationship for torsional deformation.In this paper,the Gleeble-3500 thermal simulation torsion unit is used to carry out different deformation temperatures(320°C,350°C,380°C,420°C)and deformation rates(0.1s-1,0.01s-1,0.001s-1,0.0005s-1)compression torsion deformation.The microstructure and mechanical properties of compression-torsion specimens under different deformation conditions were analyzed by OM,EBSD,and hardness tests.The research results show that:The compression-torsion deformation stress-strain curve of AZ80 magnesium alloy shows typical recrystallization characteristics,and its rheological behavior presents a competitive process of work hardening and rheological softening;the constitutive equation of the alloy with temperature compensation factor is established;the AZ80 magnesium alloy is constructed The compression-torsion deformation thermal processing diagram of the alloy obtained the optimal processing region(temperature 350 ℃ ～ 400 ℃,strain rate 0.001s-1 ～0.030s-1)and instability region(deformation temperature 320°C-350°C medium-high strain rate region and 400°C-420°C high strain rate region).The recrystallization mechanism of AZ80 magnesium alloy is continuous dynamic recrystallization and discontinuous dynamic recrystallization during compression-torsion deformation at low temperature and high strain rate.With the increase of temperature and the decrease of strain rate,recrystallization gradually develops from continuous dynamic recrystallization to discontinuous dynamic recrystallization,twins and twin dynamic recrystallization disappear,and the number of recrystallization increases.Compression-torsional deformation will weaken the initial texture of the sample to a certain extent.When the deformation temperature is low,the texture components will develop from a single basal texture to a non-basal texture,and the grain orientation will gradually revert to the basal texture as the temperature rises.The texture strength is affected by the proportion of recrystallized and deformed grains,and the texture strength is determined by both.The hardness of the sample after the compression-torsional deformation process has a certain increase compared with the original state.Increasing the deformation temperature and decreasing the strain rate will result in a decrease in the microhardness.When the deformation temperature is 320℃ and the strain rate is 0.1s-1,the hardness of the sample is the highest,which can reach 82.1HV.This study provides a theoretical basis for the development of hot forging and twisting.