Hot deformation behaviour of 7075 alloy

The hot deformation behaviour of Stir cast 7075 alloy was studied using processing map technique. The map has been interpreted in terms of the microstructural processes occurring in situ with deformation, based on the values of a dimensionless parameter eta which is an efficiency index of energy dissipation through microstructural processes. An instability criterion has also been applied to demarcate the flow instability regions in the processing map using another parameter (xi). Both the parameters (eta and xi) were computed from the experimental data generated by compression tests conducted at various temperatures and strain rate combinations over the hot working range (300-500 degrees C and 0.001-1.0 s(-1)) of the present material. The processing map exhibits one distinct eta domains without any unstable flow conditions under the investigated temperature and strain rate conditions. The dynamic recrystallization zone and instable zones, i.e. adiabatic shear band formation, interface crack, and wedge cracking, were identified in the processing map. Microstructural examination was performed for validation. The processing maps can be used to select optimum strain rates and temperatures for effective hot deformation of 7075 alloy. (C) 2010 Elsevier B.V. All rights reserved.