The Effect Of Precipitations And Twin-detwining Behaviors On The Shift Of Neutral Layer Of AZ80 Magnesium Alloy Plate

Due to its special close-packed hexagonal structure structure,magnesium alloy has fewer slip systems that can be activated at room temperature.This makes the plastic deformation ability of magnesium alloy poor at room temperature and severely limits the development of magnesium alloys.Bending is one of the deformation methods commonly used in the production of magnesium alloys,and the springback of bending has an important effect on the forming process and product precision.In this paper,the microstructure of AZ80 magnesium alloy was analyzed by means of metalloscope(OM),scanning electron microscopy(SEM),electron backscattering diffraction(EBSD)and other characterization methods.The effects of second phase particles and twin-detwinning mechanism on the shift of the bending neutral layer and springback of AZ80 magnesium alloy sheet were studied.The following conclusions are drawn:(1)The rolled AZ80 magnesium alloy sheet was precompressed along the transverse direction with deformations of 1%,3% and 5% at room temperature,then aging treatment was carried out.The detwinning behavior of the pre-twinning magnesium alloy occurs when stretched in reverse along the transverse direction,and the yield strength of the samples decreases.However,the detwinning behavior of the pre-twinning aged magnesium alloy is inhibited by the precipitation,and the yield strength of the samples is higher than the single pretwinning magnesium alloy.(2)The rolled AZ80 magnesium alloy sheet was precompressed along the transverse direction with deformations of 1%,3% and 5% at room temperature,then aging treatment was carried out.The precompression aged specimens were subjected to 90° V-shaped bending deformation at 100?.The inner and outer sides of bending produce tension and compression asymmetry,and the strain neutral layer is offset to the outer side.With the increase of the degree of precompression,the springback increases gradually.However,after pre-twinning aging treatment,the detwinning is inhibited by the second phase particles,the tension-compression asymmetry is enhanced,the migration coefficient of the neutral layer K value increases,and the springback is less than that of the pre-twinning single specimens.(3)The rolled AZ80 magnesium alloy sheet was precompressed with deformation of 1%,3% and 5% in the transverse and rolling directions respectively at room temperature,and then aging treatment was carried out.The precompression aged specimens were stretched in reverse respectively along the transverse,rolling and 45° direction.When the specimens were stretched along the transverse and rolling directions,the detwinning behavior of magnesium alloy is produced and the yield strength is reduced.After pre-twinning aging treatment,the twinning behavior is inhibited by the second phase particles,and the yield strength of the specimens increases compared with the single pre-twinning specimens.However,when the specimens were stretched along the 45° direction,the detwinning behavior is weak.(4)The rolled AZ80 magnesium alloy sheet was precompressed with deformation of 1%,3% and 5% in the transverse and rolling directions respectively at room temperature,and then aging treatment was carried out.The precompression aged specimen was subjected to 90° Vshaped bending at 100?.Tensile deformation occurs on the outside of bending and compression deformation occurs on the inside.The tension and compression asymmetry of the inner and outer sides is produced,and the strain neutral layer is offset to the outer side.The springback increases with the increasing of the precompression degree.However,after pre-twinning aging treatment,the detwinning behavior is inhibited by the second phase particles.The tension and compression asymmetry of the inner and outer sides is enhanced,the migration coefficient of the neutral layer is increased,and the springback is smaller than that of the single pre-twinning sample.(5)The bending process was simulated by ABQAUS software,and the theoretical model between the strain neutral layer of bending and the bending springback was calculated mathematically.The simulation results were verified by the mathematical theoretical model.The simulation results show that the AZ80 magnesium alloy specimens' springback occurs after bending deformation,and the strain neutral layer of bending shifts outward.The results are consistent with the actual experimental results and the calculation results of mathematical theory model.