Microstructure evolution and mechanical properties of back extruded 7075 aluminum alloy at elevated temperatures

The present work deals with the microstructural evolution and mechanical properties of 7075 aluminum alloy which has been backward extruded under different deformation conditions. The backward extrusion passes were carried out in the temperature range of 450-520 degrees C using different punch diameters (12 and 15 mm) and punch displacement velocities (5 and 25 mm/min). The results indicate that a combination of different recrystallization mechanisms (i.e., continuous, discontinuous and geometrical ones) may contribute to the formation of new recrystallized grains during applied backward extrusion process. A small specimen testing technique (shear punch testing method) was employed to evaluate the mechanical properties of backward extruded work-pieces at room temperature. The results showed that the corresponding mechanical properties have been improved through applied backward extrusion passes. It is also found that the shear strength and ductility values have been substantially influenced by the deformation temperature and punch velocity and punch diameter. (C) 2011 Elsevier B.V. All rights reserved.