The Anelasticity And Microplasticity Of AZ31 Wrought Magnesium Alloy

Magnesium alloy has potential application value in the field of lightweight manufacturing of high-end equipment due to its low density and high specific strength.However,the deformation of wrought magnesium alloy shows the characteristics of anelasticity and micro plasticity before yield,which leads to the fact that the actual elastic modulus is lower than the theoretical elastic modulus,and affects the high cycle fatigue performance,dimensional stability,damping performance and formability of magnesium alloy,resulting in the inaccuracy of basic design parameters such as elastic modulus and damping coefficient in static and dynamic mechanical design,which further restricts the deformation of magnesium alloy Alloys are widely used.In this paper,the anelastic and micro plastic behaviors of AZ31 wrought magnesium alloy before macro yield were studied by cyclic loading and unloading experiments under tension and compression.The non-linear elastic micro mechanism of wrought magnesium alloy was revealed by means of material characterization and texture analysis.The effects of different types of initial textures on the non-linear elastic deformation of AZ31 rolled sheet and extruded bar were studied,and the effects of preset dislocations on the non-linear elastic deformation were studied by 6% pre tensile strain.Tensile and compression loading and unloading experiments were carried out along the direction of rolling direction(RD)at0 °,45 ° and 90 ° for rolled plate,and tensile loading and unloading experiments were carried out for extruded bar along the extrusion direction.By analyzing the pole diagram and orientation distribution function(ODF)diagram,the non-linear elastic micro mechanism of wrought magnesium alloy was clarified.The results show that as following:(1)The non-linear elastic behavior of AZ31 magnesium alloy before yielding has strong tension compression asymmetry and anisotropy.In the process of tension,micro plasticity is dominant,while in the process of compression,anelasticity is dominant.(2)Compared with the initial deformation,the micro plasticity disappears after pretension under the same stress,showing a weak anelasticity,but there is still anisotropic behavior.The elastic deformation ability of wrought magnesium alloy can be improved by pre deformation.(3)The movement of dislocations in the material leads to the change of texture during deformation before yielding.However,the dislocation does not cause a sharp decrease in the elastic modulus.The difference of Schmid factor caused by texture along different directions is the reason of non-linear elastic anisotropy.The asymmetry of tension and compression nonlinearities is due to the inhibition of twinning nucleus on the propagation of short-range dislocations.(4)A variable elastic modulus model including stress factor was constructed to accurately characterize the tension compression asymmetry of AZ31 wrought magnesium alloy.