On microstructure and texture heterogeneities in single crystals deformed by equal channel angular extrusion

On the processing of hetero-nanostructured metals for improved strength/ductility balance by ECAE and SPS techniques

“…Due to structural and textural heterogeneities developed with these processes as well as a high content of stored energy, annealing of nanostructured metals is difficult to control because of the occurrence of non-uniform coarsening and recrystallization. These deformation heterogeneities are for example particularly present at the scale of the billet of ECAE processed materials [14][15][16]. Therefore, as also exemplified recently by the sub-surface heterogeneous recrystallized structures observed after one-step annealing of ARD deformed samples, a two-step annealing procedure is often required to avoid discontinuous recrystallization [17].…”

Local texture and microstructure in cube-oriented nickel single crystal deformed by equal channel angular extrusion

“…The cross-section is characterized by a heterogeneous banded microstructure. As depicted in [26], excluding the two layers experiencing the direct effect of the friction on the lower and upper die walls (800 and 500 mm thick, respectively), the rest of the billet section can be divided into different zones characterized by different aspects of the deformation patterns.…”

“…When the deformation heterogeneities are addressed experimentally, single crystals are preferred to polycrystals, as they can provide a simplified and deeper insight into the complex phenomenon of plastic deformation. Only a few such studies have been carried out on copper [19][20][21], aluminum [22,23] and nickel [24][25][26], as well as Nb [27] single crystals. On the other hand, different types of microstructures and textures were observed in these ECAEdeformed single crystals, which were attributed to the formation of local deformation heterogeneities, such as deformation and/or shear bands.…”

“…However, significant variations in texture and microstructure were also observed in ECAE-deformed single crystals along the billet height [14,24]. In addition, the recent analysis of a cube-oriented nickel single crystal extruded through a squaresection die also revealed strong differences in deformation pattern along the transverse direction of the extruded material [26]. These changes in deformation mechanisms resulted in significant macroscopic deformation heterogeneities on the overall crosssection of the sample, even when a single crystal was used [26].…”

Creep properties of aluminium processed by ECAP

“…Thus, in single crystals subjected to SPD, all grain boundaries are formed during deformation. To date, very limited experiments paid attention to the effect of initial crystallographic orientation on the evolution and mechanical properties of ultrafine-grained structure [5][6][7][8][9], but the most of the works on single crystals were concerned with processing only after 1 ECAP pass. It was suggested that the evolution of microstructure relates to the concentration of activated slip systems with respect to the shear plane.…”