Processing maps for hot working of a P/M iron aluminide alloy

The hot working behavior of a Fe-24 wt.% Al iron aluminide alloy processed by the powder metallurgy route has been studied in the temperature range 750-1150°C and strain rate range $0.001-100 \hspace{2mm}s^{-1}$ by establishing processing maps at different strains in the range 0.1-0.5. The features in the processing maps have changed with strain suggesting that the mechanisms of hot deformation are evolving with strain. Early in the deformation (strain of 0.1), the map exhibited a single domain with a peak efficiency of power dissipation of about 44% occurring at about 1100°C and a strain rate of about $0.03 \hspace{2mm} s^{-1}$. This domain represents dynamic recrystallization (DRX) of the initial material possibly causing a substantial grain refinement. With increasing strain, a bifurcation has occurred giving rise to two domains: (1) at strain rates lower than about $0.1 \hspace{2mm}s^{-1}$ and temperatures above 1000°C, superplastic deformation has occurred, and (2) at strain rates higher than about $10 \hspace{2mm}s^{-1} $ and temperatures above 1125°C, DRX has occurred. The material exhibited flow localization at lower temperatures and higher strain rates. On the basis of the processing maps, the optimum processing routes available for hot working of this material are outlined