Effects of stored strain energy on restoration mechanisms and texture components in an aluminum-magnesium alloy prepared by friction stir processing

Plates of AA5052 (Al-Mg) alloy in both annealed (solution-treated) and wrought (rolled) temper conditions were subjected to friction stir processing (FSP) at various w/v pitch ratios from 4 to 28 rev.min/mm. The role of stored strain energy on the evolution of restoration mechanisms and crystallographic texture components were assessed in terms of microstructural features evaluated using electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM) analysis. The results revealed that FSP significantly refined the grain structure and changed the crystallographic micro-texture components. The grain size of the annealed and wrought alloy was reduced from 49.4 and 9.7 μm initial values to 3.3 and 3.6 μm, respectively when w/v=4. Also, the formation of a {112}⟨110⟩ crystallographic shear texture with a strong B/B¯ component intensity were observed. The microstructural changes in the annealed alloy were related to the occurrence of discontinuous dynamic recrystallization (DDRX) mechanism, while operation of a static recrystallization (SRX) prior to a continuous (CDRX) mode in the wrought one, revealing the effect of stored strain energy. Evaluations of the mechanical properties also determined enhanced ultimate tensile strength, elongation, and indentation Vickers hardness while preserving the yield stress.