Recent advances in B2 iron aluminide alloys: deformation, fracture and alloy design

This paper reviews the deformation, fracture and alloy design of B2 iron aluminides based on FeAl. Moisture-induced environmental embrittlement is shown to be a leading cause of low tensile ductility and brittle cleavage fracture of Ferich FeAl alloys at ambient temperatures. With increasing Al concentration, two other factors, namely intrinsic grain-boundary weakness and quenched-in vacancies become important in limiting the tensile ductility of FeAl alloys. FeAl alloys show a yield-strength anomaly at intermediate temperatures. Recent work indicates that the anomaly is a result of hardening by thermal vacancies at elevated temperatures. The understanding of the deformation and fracture behavior has led to the development of FeAl-base alloys and composites with improved metallurgical and mechanical properties for structural applications. These FeAl-based alloys can be prepared by melting and casting or by powder processing. The unique combination of the excellent oxidation and carburization/sulfidation resistance coupled with relatively low material density and good mechanical properties at room and elevated temperatures has sparked industrial interest in FeAl alloys and composites for a number of applications.