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

This paper reviews the deformation, fracture and alloy design of B2 iron al uminides based on FeAl. Moisture-induced environmental embrittlement is sho wn to be a leading cause of low tensile ductility and brittle cleavage frac ture of Fe-rich FeAl alloys at ambient temperatures. With increasing Al con centration, two other factors, namely intrinsic grain-boundary weakness and quenched-in vacancies become important in limiting the tensile ductility o f FeAl alloys. FeAl alloys show a yield-strength anomaly at intermediate te mperatures. Recent work indicates that the anomaly is a result of hardening by thermal vacancies at elevated temperatures. The understanding of the de formation and fracture behavior has led to the development of FeAl-base all oys and composites with improved metallurgical and mechanical properties fo r structural applications. These FeAl-based alloys can be prepared by melti ng and casting or by powder processing. The unique combination of the excel lent oxidation and carburization/sulfidation resistance coupled with relati vely low material density and good mechanical properties at room and elevat ed temperatures has sparked industrial interest in FeAl alloys and composit es for a number of applications. (C) 1998 Elsevier Science S.A. All rights reserved.