Processing of iron aluminides

Abstract

A processing route comprising of air induction melting (AIM) with protective cover and electroslag remelting (ESR) for production of iron aluminide (Fe₃Al) alloys has been developed. The use of protective cover during AIM results in the minimization of hydrogen gas porosity and a significant reduction in the impurity levels (S, O and N). Attempts have been made to further improve the ductility and hot workability through ESR. The AIM melted with high carbon ingots exhibit excellent tensile properties compared to the low (<0.074 wt.%) carbon ingots where cracks persist even after ESR. Processing maps were developed for vacuum induction melted as-cast binary and ternary (Cr and Mn) Fe₃Al alloys. Processing maps of Fe₃Al and Fe₃Al–Cr exhibit a dynamic recrystallisation domain at temperatures >1123 K. Dynamic recrystallisation in iron aluminides is controlled by migration of interfaces. In the case of Fe₃Al–Mn, dynamic recrystallisation is suppressed due to greater resistance to the migration of interfaces. Instead, large grain superplasticity is observed.