Development of Processing Maps and Constitutive Relationship for Thermomechanical Processing of Aluminum Alloy AA2219

Abstract

Isothermal uniaxial compression tests were conducted on aluminum alloy AA2219 to study the evolution of microstructure over a wide range of temperatures (300-500 °C) and strain rates (0.001-100 s−1) with a view to study the flow behavior and concurrent microstructural evolution. True stress-true strain curves showed only a gradual flow softening at all temperatures except at 300 °C where strain hardening was followed by severe flow softening. Processing map delineating the stable ‘safe’ and unstable ‘unsafe’ regions during hot working is developed and validated by comparing the microstructures observed in the deformed compression specimens. Optimum processing parameters (temperature 450 °C and strain rate 0.001 s−1) for hot deformation of AA2219 were proposed based on contour maps of efficiency of power dissipation and strain rate sensitivity parameter. The activation energy value (Qavg) of AA2219 for hot working was computed to be 169 kJ/mol. Finally, a constitutive equation for hot working of AA2219 was established as: \(\dot{\varepsilon } = 4.99 \times 10^{9} \cdot \exp (0.06149\sigma ) \cdot \exp \left( { - 168.958/RT} \right)\).