Effects Of Grain Size On The Shift Of Neutral Layer And Springback Of AZ31Magnesium Alloy Sheet

Due to the close-packedhexagonalstructure of magnesium alloy, the (0001) basalslip is the only slip plane at room temperature.So magnesium alloy sheet shows largetension-compression asymmetry. The neutral layer tends to shift to the outer filebecause of the different deformation mechanism in inner and outer region duringbending. The grain size has a great influence on the tension-compression asymmetry ofmagnesium alloy. However, the reports about the effects of grain size on the shift ofneutral layer and springback of AZ31magnesium alloy sheet were rarely showed. Sothe paper would be systematical to research the effects of grain size on the shift ofneutral layer of AZ31magnesium alloy. The microstructure evolution of magnesiumalloy sheets with different grain sizes during bending was investigated bymetallographic microscope and electron back scattering diffraction (EBSD).Usingmechanical testing to explore the relationship between the shift of neutral layer andspringback and mechanical property. The main research contents and results are asfollows:①After the V-bending test of AZ31magnesium alloy sheet with an angle of90°,the neutral layer shifted to the outer region. With increasing of grain size, thecoefficient of neutral layer value (k-value) increased, the k value was0.636，0.647，0.663，0.677, respectively(when the k value is greater than0.5, the neutral layer shifts toouter file).②After the V-bending test, the AZ31magnesium alloy sheets occurredspringback and the springback value is about25°. The springback angle decreaseswith the increasing grain size. The springback angles are25.50°，25.33°，25.17°，24.83°, respectively.③The tensile and compression tests of the four groups of magnesium alloy sheetwith different grain sizes are carried out at150℃.The results show that CYS/TYS valueare0.89，0.87，0.85，0.78, respectively, with increasing grain size and the enhancedtension-compression asymmetry.④The rolled magnesium alloy sheet has a strong (0001) basal texture. Thetension deformation in outer region results the texture strength become strongersignificantly during bending. The compression deformation in inner region forms{10-12} twins and makes the most of the grain orientation rotated about86°. At the moment, the texture intensity of inner region is weakened compared to the outer region.A clear twin dividing line in the middle region of V-bended specimen can be observed.Twins is more likely to appear in inner region during bending with increasing grain size.