The microstructure developed during severe plastic deformation results in improved mechanical properties because of the decrease in domain sizes and accumulation of defects, mainly dislocation arrays. The characteristic deformation stages observed in low stacking fault energy (SFE) face centered cubic (FCC) materials are highly influenced by the development of the primary and secondary twinning that compete with dislocation glide. In this paper, a low SFE F138 stainless steel is deformed by equal channel angular pressing (ECAP) up to 4 passes at room temperature (RT) and at 300°C to compare the grain refinement and twin boundary development with increasing deformation. Tensile tests were performed to determine the deformation stages reached by the material before and after ECAP deformation, and the resulting microstructure was observed by TEM. X-ray diffraction and EBSD, average technique the first and local the second one, were used to quantify the microstructural changes, allowing the determination of diffraction domain sizes, dislocation and stacking fault densities and misorientation indices, which lead to a complete analysis of the deformation introduced in the material, with comparative correlations between various microstructural parameters.

No abstract

The texture-induced anisotropic mechanical behavior of a highly textured AA 7020-T6 (maximum orientation density of 29.7 multiple random distribution), was characterized by the lattice strain evolution along rolling direction (RD), 45° to RD and 90° to RD, respectively, under uniaxial tension using high energy X-ray diffraction. The uniaxial tensile tests were done till ultimate tensile strength (UTS), which show different yield strengths (YS), UTS and elongations along the three directions on a macroscopic level. On micromechanical level, the lattice strain evolution explains the correlation between crystallite orientation and different mechanical behavior, leading to the macroscopic anisotropy. In the elastic region, the sample 45° to RD has the lowest lattice plane dependent Young's modulus compared to the other two directions. In the elastic plastic transition region, lattice strain differences among different {hkl} lattice planes are highest for sample 45° to RD and lowest for sample 0° to RD. Moreover, the 45° to RD sample has the lowest lattice dependent YS. In the plastic region, the work hardening behavior of different {hkl} lattice planes in all three directions can be divided into two groups, corresponding to two types of dislocation combinations. However, {200} planes of samples 45° and 90° to RD behave abnormally due to the stress along <110> of the {200} planes and the orientation density of {200} planes parallel and perpendicular to the loading direction (LD).

Two-Sites Self-Consistent (2-SSC) models have been used for simulation of texture development oftwo-phase materials (Bolmaro and Lebensohn, 1996;Bolmaro et al., 1997).When both phases are plastically deforming the co-deformation and sharing of spins have to be taken into account via interaction among phases. One-Site Self-Consistent (1-SSC) models are able to consider interaction among each grain and the rest ofsurrounding grains through a mean field calculated over the "matrix grains". The next level ofcomplexity, i.e., 2-SSC models, is appropriate to capture some interaction features between phases. In the current paper, starting from well-defined microstructures and textures of Cu-Fe powder composites, the textures obtained after wire-drawing are simulated taking into account codeformation and sharing of rotations. The results are shown agreeing with experimental ones provided that, depending on volume fraction and relative strength of both phases, different ad-hoc strain rate sensitivities are used.