The change in crystallographic orientation distribution during high temperature deformation for an Al-Mg-Mn alloy sheet consisting of the coarse-grained surface and the fine-grained center layers has been investigated in order to reveal the deformation mechanism. The grain size dependence of the deformation behavior is discussed in the identical deformation condition by using the specially-prepared sheet. The grain structures in the coarse-grained surface layer of the sample deformed at 713 K are elongated in the tensile direction corresponding to the macroscopic elongation to failure. The structures related to the maximum elongation in both of the surface and center layers have preferred orientations of the tensile deformation. Further, the intragranular misorientation, grain boundary misorientation and high strain rate deformation are analyzed in detail.

Changes in crystallographic orientation distribution during superplastic deformation in a fine-grained Al-Zn-Mg-Cu alloy and an Al-Mg-Mn alloy consisting of the coarse-grained surface and the fine-grained center layers have been reviewed in order to reveal contribution of dislocation slips to deformation. The strain rate and grain size dependences of the deformation behavior were examined by SEM/EBSD (scanning electron microscopy/ electron back scatter diffraction) analysis. Intragranular misorientation increases after deformation at high strain rates, presumably due to dislocation activity, while it was low in the specimen deformed at a low strain rate in the early stage of 35% strain. Progressive randomization of the initial texture was also found during deformation at the low strain rate. Further, grain structure and grain boundary character are analyzed in detail to discuss the deformation mechanism.

High temperature deformation and crystallographic orientation distribution of the Al-Mg-Mn sheet worked by the continuous cyclic bending (CCB) and the subsequent annealing have been investigated. The sheet consists of a coarse-grained surface and fine-grained center layers. The elongation to failure has a peak value at 713K at initial strain rates of 5.6×10 -4 s -1 and 5.6×10 -3 s -1 in both of as-received sample (0P) with fine grains and CCBent and annealed one (20P_A) with the coarse and the fine grains in spite of different microstructures. The m value decreases for 20P_A and increases for 0P with increasing temperature. However, the increase of the m value is not correspondent to the change in the elongation. The deformation mechanism is discussed with relation to activation energy. The SEM micrographs of the original surfaces of tensile specimens deformed to failure reveal that at the relatively high temperatures many cracks are formed inside the coarse grains. The change in crystallographic orientation distribution is investigated during tensile testing in consideration of the deformation mechanism.