Mechanical Behavior of Chromium and Titanium Alloyed Iron Aluminides with Mischmetal Addition

Abstract

Iron aluminides based on the stoichiometric compositions of Fe{sub 3}Al and FeAl are candidate high temperature materials due to their excellent oxidation and sulfidation resistance. However, they exhibit poor room temperature ductilities due to hydrogen embrittlement (HE). The addition of Cr is very effective in minimizing HE, the cause of which has been elucidated from an electrochemical viewpoint. It has been proposed that alloying Fe{sub 3}Al with passivity-inducing elements would reduce hydrogen liberation rates on the surfaces of iron aluminides thereby minimizing HE. Only the Cr- and Ti-alloyed intermetallics exhibited ductility. The other intermetallics were brittle due to the precipitation of additional brittle phases. In light of these results, three alloyed iron aluminides were prepared keeping the total alloying amount minimum (2%). It has been reported that small Ce additions enhance the ductility of iron aluminides. Therefore, a small amount of Mm (Indian Mischmetal) was also added to these intermetallics as it is known that one of the major components of Mm is Ce. The present communication reports the mechanical behavior of these alloyed iron aluminides.