Iron Aluminides

Abstract

Iron aluminides have been of interest since the 1930s when the excellent corrosion resistance of compositions with more than about 18 at% Al was first noted (DeVan 1989; Ziegler 1932). These alloys offer relatively low material cost, conservation of strategic elements, and a lower density than stainless steels. Their tensile strength also compares favorably with many ferritic and austenitic steels. These property advantages have led to the consideration of iron-aluminum alloys for many applications including those listed in Table 9–1 (McKamey et al. 1991; Nachman and Buehler 1956; Sikka et al. 1993). However, limited ductility at ambient temperatures and a sharp drop in strength above 600° C have been major deterrents to their acceptance for many structural applications. More recent studies have demonstrated that improved engineering ductility (to 10–15% in Fe3Al) can be achieved in wrought Fe3Al-based iron aluminide alloys through control of composition and microstructure (Bordeau 1987; Culbertson and Kortovich 1986; Sikka 1991b; Sikka et al. 1993). Accompanying this improvement has been an increased understanding of the causes for ambient temperature embrittlement in this system (Liu et al. 1989, 1990; McKamey and Liu 1992). Because of these advances, iron-aluminide alloys (especially those of up to 50 at% Al) are again being considered for structural uses, especially for applications where their excellent corrosion resistance can be exploited.