Equal channel angular pressing (ECAP) is a severe plastic deformation (SPD) technique that produces nanostructured materials. Based on a remarkable grain size reduction, this process has led to improve mechanical properties, such as yield strength, fatigue, UTS, etc. In this work the characterization of the microstructure of the aluminum 6061-T6 alloy; plastically deformed up to ¾ μ 6, by the ECAP process, following route Bc, is presented. For this purpose, the ECAP processed samples were characterized by means of X-ray diffraction (for texture and line profile analysis) and transmission electron microscopy. The initial crystallographic texture vanished after one ECAP pass and a new, well defined, shear texture C ª was generated. For the subsequent ECAP passes, more shear components: A Ã 1ª , B ª and B ª were also developed. From the orientation distribution function analysis, a shift (generally less than 15°) between some experimental maxima and the reported ideal shear texture positions was observed. From these results, it was found that the microstructure generated with this process was stabilized after the 5th ECAP pass. Finally, the micro-strain analyses, in addition to the texture and transmission electron microscopy, contributed to the understanding of the effect of the physical and mechanical processes that were activated during the SPD-ECAP technique.
There is a lack of information with regards to the friction effect in ECAPed aluminum alloys, even though it might substantially modify the deformation at the surface. In this work, the friction effect at the surface and the deformation heterogeneity in the ECAPed aluminum alloy 6061-T6 were characterized. X-Ray diffraction was used to determine residual stresses (RS) on the sample surface. The volumetric sections were characterized by Synchrotron diffraction at ESRF beamline ID15B (Grenoble, France). It was found that the microhardness mapping and residual stress results showed a good agreement with the finite element analysis for the first layer studied. Minor strain variation, Delta d/d as a function of (hkl) planes, for the different analyzed sections was found. The study also showed that there was an incomplete symmetry in the residual stress near the surface, even at up to a depth of 400 gm. The regions with higher deformation were found to be at the top and bottom parts of the sample, while the central region showed stress variations of up to 50 MPa. (C) 2016 Elsevier B.V. All rights reserved.Peer ReviewedPostprint (published version
A B S T R A C TThe mechanical behavior and microstructural evolution of an AA2017 aluminum alloy processed by ECAP with an equivalent simple shear deformation of ∼6 at 200°C were studied. Samples were characterized by means of scanning electron microscopy (SEM-EDS-EBSD), image-assisted by focus ion beam (FIB), Vickers microhardness and X-ray diffraction (XRD) techniques. During the deformation process, the Al 2 Cu precipitates did not get fragmented or re-absorbed in the Al matrix. After the first ECAP pass, at least 50% of grains displayed an ultrafine size. The EBSD analysis showed an increment of the misorientation angle immediately after the first ECAP pass. The macrotexture evolution was explained in terms of the formation of f1: A 1θ * , A θ , Ā θ , A 2θ * , f2: C θ , θ , B θ , Ā θ , A θ , A 1θ * and f3: C θ , B θ , θ , A θ , Ā θ , A 2θ * fibers. The macro-residual stress measurements of the highly deformed samples showed linear sin 2 ψ profiles. The micro and macro-residual stresses were compatible with dislocation rearrangement, in which the annihilation and formation were in quasi-equilibrium. It was found that the highest microhardness value (1176 MPa) and grain refinement (at least 20% of grains showed a size smaller than 100 μm 2 ) appeared after the first extrusion pass. The decrease in hardness, after the second pass and the residual stress stability, could be associated to a dynamic recovery phenomenon.
Forging is a widely used manufacturing process, and its design and modeling are important to reducing production costs, increasing die lifespan, and improving the mechanical properties of the final product. In this study, the forging process of a connecting rod was modeled using 3D coupled Eulerian Lagrangian (CEL) analysis by FEM. The methodology adopted achieved to determine a preform geometry that reduces final flash and forging load, while ensuring complete filling of the stamp. Starting from the final geometry, the final die was designed. After the first result for an approximately 27% of flash, the material distribution was adjusted decreasing it at the regions where the flash was too large. After an iterative method was applied to determine better preform, a proposal was found that reduced forging force by approximately 42% and the percentage of flash volume by 64% in comparison with the first one. A final flash of about 10% is considered a good objective to reach. Lower values may cause many iterations, not a significant difference in forging loads, the risk of an unfilled die, and complex preform geometries.
Among the severe plastic deformation techniques, the equal channel angular pressing (ECAP) has drastically improved the mechanical properties of the processed alloys. However, information regarding friction phenomenon, which modifies the deformation at the surface and the heterogeneity microstrain state produced by the process itself, is still scarce. In the present work, the deformation heterogeneity and the friction effect, at the surface in the bulk material of the 6061-T6 aluminum alloy processed by ECAP, is presented and discussed. The residual stress (RS) measurements were performed by means of X-Ray diffraction. By means of synchrotron diffraction, volumetric sections of the ECAPed samples were characterized. Finite element analysis showed a good agreement with the experimentally obtained residual stress and microhardness mapping results. The study also showed that the highest deformation zones were located at the outer parts of the deformed samples (top and bottom), while the inner zone showed strain oscillations of up to 49±2 MPa.
Forging is a widely used manufacturing processes and its design and modeling are important to reducing production costs, increasing die lifespan and improving the mechanical properties of the final product. In this study, the forging process of a connecting rod was modeled using 3D Coupled Eulerian Lagrangian (CEL) analysis by FEM. The methodology adopted achieved to determine a preform geometry that reduces final flash and forging load, while ensuring complete filling of the stamp. Starting from the final geometry, the final die was designed. After the first result for an approximately 27% of flash, it was adjusted the material distribution decreasing it at the regions where the flash was too large. After an iterative method was applied to determine better preform, a proposal was found that reduced forging force by approximately 42% and the percentage of flash volume by 64% in comparison with the first one. A final flash of about 10% is considered a good objective to reach. Lower values may cause many iterations, not a significant difference in forging loads, the risk of an unfilled die and complex preform geometries.
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