PSI - Issue 43

Orsolya Molnárová et al. / Procedia Structural Integrity 43 (2023) 166–171 Author name / Structural Integrity Procedia 00 (2022) 000 – 000

169

4

The orientation relationships in locality 2 are complicated by the fact that during the 1 st ECAP-like deformation the material deforms with rotational symmetry to form a tube. Due to that rotational symmetry, we can only discuss preferred orientations in the direction of the deformation. The microstructure at locality 2 exhibits two preferred orientations in the direction of deformation, a stronger one is  156  and the slightly weaker is  235  (Fig. 4c). These orientations are mutually related by 45°  100  rotation. These orientations resulted from the flow of the material in the direction perpendicular to the original deformation direction. The existence of a belt of pronounced orientations might be joined with changing the direction of prolonged grains in the material.

Fig. 2. Locality 1; (a) IPF map with color triangle and character of the grain boundaries; (b) KAM map with misorientation scale; (c) IPF in direction of the CSET processing with intensity scale.

Fig. 3. Locality 1a; (a) IPF map with color triangle (b) IPF in direction of the CSET processing with intensity scale.

The microstructure of aluminum after 2 nd ECAP-like deformation (locality 3) exhibits prolonged grains in direction of the deformation (Fig. 5a). Their size and shape are very similar to those at locality 2 and fall into the category of submicrometer size. The fact that there is no further grain refinement after the ECAP-like deformation suggests that this size seems to be a limit for pure aluminum (cf. Mohammadi et al., 2021). Maximum density of dislocations was estimated to be of about 3  10 15 m – 2 in this region. The microstructure at locality 3 which is close to the inner wall of the tube is – in contrast to those in the center of the tube or close to the outer wall – recrystallized to a quite large extent (Fig. 6). This is a consequence of high deformation caused by the shear deformation induced by the rotating mandrel which provided the enhanced driving force for room temperature recrystallization. The preferred orientation at this locality is formed by a strong  355  and a weak  001  components (Fig. 5c). Due to a complex deformation and recrystallization processes, it is hard to describe any orientation relationship either with