Microanalysis of crystallographic characteristics and structural transformations in SPDed Al-Mn-Si alloy by dual-straining

Dual-straining paths through constrained groove pressing (CGP) and post-rolling were applied on Al-Mn-Si sheet. CGPed specimens were subsequently cold-rolled by 0.47, 0.8 and 1.27 strains along direct and cross orientations. Microstructural studies depicted production of semi-elongated and lamellar structure by CGP and rolling, respectively. X-ray diffraction (XRD) patterns demonstrated the dominant effect of rolling on CGP in dual-strained specimens since (111) and (220) crystallographic planes were attenuated and (311) planes were intensified by complementary reductions. Changes for crystallite size, dislocation density and lattice strain were traced and results showed that dynamic recrystallization (DRX) started from lower strains due to dual-straining condition. While the minimum crystallite size of 360 nm obtained by 0.47 strain, single-rolling of annealed alloy up to 1.27 strain attained coarser crystallites in the range of starting material (723 nm). Rolling of CGPed sheet formed crystallites with average size of 619 and 593 nm in direct and cross orientations, respectively. As direct-rolling was more efficient on DRX occurrence and crystallites' growth, dislocation density and lattice strain were both declined by further straining and reached 0.57 x 10(13) m(-2) and 0.173 epsilon(L), respectively. Using diffraction principles, peak shiftings were analyzed and d-spacing was calculated systematically for (111) planes. Accordingly, single-rolling rather than CGP caused lattice swelling due to DRX; however, in dual-strained specimens lattice compactness was examined. Mechanical properties of fabricated specimens were acquired by tension and hardness tests. Maximum ultimate tensile strength (UTS) and yield strength (YS) of 196 and 141 MPa were examined for CGPed+1.27 direct-rolled specimen. Meanwhile, elongation to failure of 5.24% was tested for two-pass CGPed alloy and this was diminished to 2.63% in CGPed+1.27 cross-rolled sample. Mechanically absorbed energy during tensile testing was calculated while tougher specimen (CGPed+0.8 direct-rolled) absorbed 6.3 J m(-3). The minimum energy value of 2.75 J m(-3) was for CGPed+1.27 cross-rolled specimen. (C) 2016 Elsevier B.V. All rights reserved.