Texture weakening of AZ31 magnesium alloy sheet obtained by a combination of bidirectional cyclic bending at low temperature and static recrystallization

In this work, the grain refinement and texture weakening in the sheets of AZ31 magnesium alloy were studied by means of bidirectional cyclic bending for 6 passes at 423 K and subsequent static recrystallization (SRX) on two annealing conditions. The deformed and annealed samples were examined by optical microscopy and electron backscatter diffraction analysis. The results showed that a gradient structure with fine grains in the regions near the surfaces and, in contrast, coarse grains in the middle of the sheet were induced. The texture of the annealed samples was dramatically weakened, and the intensity decreased gradually from the center of the sheet to two surfaces. The different SRX mechanisms significantly affected the different weakening for the basal texture. The cumulative strain energy achieved by twinning played a more important role in the formation of an asymmetric gradient texture intensity distribution after annealing at 523 K for 1000 s. On the contrary, thermal energy dominated a symmetric gradient under annealing at 573 K for 100 s because of the preferential growth of new grains produced by SRX. The ductility is enhanced outstandingly with no remarkable improvement for the strength.