Theoretical and experimental study on severe plastic deformation of Aluminum sheet
Abstract:
Nowadays, according to the need of different industries to the materials with high strength to weight ratio, methods of severe plastic deformation have attracted the attention of researchers. The pressing in constrained grooved molds is one of the most effective methods of severe plastic deformation to produce sheet metal with a very fine structure. In this research, constrained groove pressing (CGP) process on aluminum 6061 alloy sheet has been studied numerically and experimentally. For this purpose, the CGP process up to two complete passes was simulated on aluminum 6061 sheet, using ABACUS finite element software to assess the accumulated strain and forming force. The finite element model was validated with the published analytical relations and was used to investigate the effect of geometric parameters on the CGP process. Finally, using the response surface method some relations were developed that were able to estimate the strain and its scattering relative to the parameters, accurately. The CGP process was conducted up to two complete passes, experimentally. After the process, in order to study the mechanical properties of the worked sheets, tensile and micro-hardness tests were performed and the microstructure of these sheets was investigated using the optical microscopy. The results of micro-hardness showed that, the hardness average value after pass one is increased 41.7 and 48.9 percent in longitudinal and thickness directions, respectively. Similarly, after pass two the hardness average value is increased 52.7 and 58.9 in longitudinal and thickness directions, respectively. The results of tensile tests showed that the CGP process causes to 122 percent increase in yield strength after pass one and 150 percent after pass two. The optical microscopy showed the average grain size is decreased after both pass one and pass two. However, the grain size reduction after pass two is less than the grain size reduction after pass one. In addition, it was observed that the average grain size reduction in the thickness direction is less than the average grain size reduction in longitudinal direction.