مهدی شبان غازانی

Grain refinement improves the mechanical properties and formability of metals and alloys. So far, several different grain refinement methods have been proposed and studied. Severe plastic deformation is one of the most promising and efficient methods. Therefore, in the present study the possibility of imposing a two-step severe plastic deformation (Extrusion and Equal channel angular pressing) on AA7075 alloy using a special designed die is investigated. Using this method, a very coarse grained microstructure with grain size of 94µm is refined to grain size of 7.5µm. Also, microstructural developments during severe deformation with and without preheating are investigated. Plastic strain distribution and temperature variation inside deformed samples are predicted by the use of thermal coupled displacement 3D finite element method. Results of FEM simulations clearly showes that the plastic strain distribution and temperature is non-uniform in sample and this introduces inhomogeneity in the resultant microstructure of sample at different regions.