Hot Workability and Microstructure Control of Aluminum-2.5 Copper-1.5 Magnesium Alloy

Abstract

Aluminum-2.5 copper-1.5 magnesium alloy is an important aerospace alloy and is extensively used in the fabrication of aerospace and aircraft systems. Hot working parameters for the alloy have been generated through hot isothermal compression testing at different temperatures (673–748 K at an interval of 25 K) and at strain rates of 0.01 to 10 s−1. Hot workability of alloy has been established by using the instability criteria and validating the same with microstructural evolution. Further, the Holloman parameter was calculated, and the constitutive equation has been derived. Optimum parameters for the hot deformation were evolved avoiding the unstable metal flow regimes of 673–760 K at 0.1 to 1 s−1. Maximum power efficiency in the dynamic recrystallization domain of the alloy is found to be ∼0.6, indicating stable material flow during hot deformation. Strain rate sensitivity (m) value of 0.25–0.35 is observed in the stable regime at strain rates of 0.01–0.1 from 698 to 748 K indicating superplastic flow domain. Very fine recrystallized grains can be seen at higher temperatures greater than 723 K and lower strain rates of 0.1 and 0.01 s−1, which grow further with an increase in temperature, indicating onset of grain growth.