TEM and SEM analyses of the orientation relations of recrystallized grains in a stable Al–1 wt.%Mn single crystal

The recrystallization grain orientations developed during annealing of a deformed single crystal have been characterized by in-situ TEM and ex-situ SEM. Single crystal samples of Al–1 wt.%Mn alloy of brass(110) [1-1-2] orientation were deformed in a channel-die to develop 2 sets of intersecting microbands at strains of 0.51 and 0.92 and then lightly annealed. Local orientation measurements demonstrate a strong relation between the deformed orientations and the limited number of recrystallized grain orientation groups. The misorientation angles across the recrystallization front were grouped in the range 25–55° (with a maximum near 40–45°) around axes located near three normals of the 4 {111} planes; the [1-11] rotation axis parallel to the transverse direction was not found. Two groups of rotation axes were identified: (i) rotation axes very close to the < 111 > or < 112 > directions, and (ii) a scattered sequence between < 111 >–< 112 >, < 111 >–< 122 > or < 122 >–< 012 > directions. The orientations of new grains that nucleate during thin foil heating in TEM were compared with those formed during static recrystallization of bulk samples analysed by SEM/EBSD, both in the centre section of electropolished samples and in near-surface areas of abraded samples. In all experiments the new grain orientations belong to the same groups and the distribution of misorientation axes across the recrystallization front was similar.

The experimental investigations have focused on an analysis of transformations which occur in Al–1 wt.%Mn alloy single crystals of brass{110}< 112 > orientations, stable during plane strain compression (PSC), i.e. without macroscopic lattice rotations. The new grains orientations measured during recrystallization of thin foils in TEM are compared with the orientations of the grains that nucleate in the centre sections of bulk samples and those near the free surface of abraded samples. The results are discussed in terms of the misorientation angle and axis distributions. The basic research techniques employed TEM equipped with a semi-automatic facility for local orientation measurements and SEM equipped with EBSD facility.Fig. 1. The distribution of new grain orientations (a) and misorientation axes across the recrystallization front (b) obtained during heating in TEM compared with the results obtained in the middle section of the bulk sample after static annealing. Red points are the results obtained during in-situ heating in TEM, whereas the new grain orientations presented in continuous form on the {111} pole figure in (a) and the black points in (b) are the results obtained during annealing of bulk samples. Local orientation measurements in TEM vs. SEM/EBSD ones. Grey circles mark the deformed state orientations.(For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)Figure optionsDownload as PowerPoint slide