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 η 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 (ξ). Both the parameters (η and ξ) 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 °C and 0.001–1.0 s−1) of the present material. The processing map exhibits one distinct η 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.

Research highlights▶ High strength to weight ratio aluminium (Al) and its alloys find their potential application in various automobile and aerospace components. ▶ The mechanical properties are closely related to the microstructure which is greatly influenced by thermo mechanical processing. So it is necessary to find the effects of thermo mechanical parameters, such as deformation temperature and strain rate, on the microstructure of the material. ▶ An understanding of constitutive behaviour of the material is essential for the optimization of the intrinsic workability and control of microstructural evolution during hot working. ▶ Trial and error techniques are both expensive and time consuming and may not lead to successful solution or optimization. Hence, these techniques are replaced with material modeling which are developed on science based principles. ▶ Process modeling is knowledge of the material flow behaviour for defining deformation. Processing maps delineate “safe” and “nonsafe” hot working conditions. These maps show in the processing space, and to establish the safe and unsafe domains.