Abstract

Iron aluminides based on Fe{sub 3}Al exhibit good oxidation as well as excellent resistance to abrasive wear and erosion. However, a major drawback for iron aluminides is their poor ductility and low fracture toughness at ambient temperature. Although considerable efforts have been devoted to understanding and improving their ductility through various techniques, the question concerning iron aluminides has always been why they are brittle at room temperature when they apparently have all the intrinsic characteristics required of good ductility. For example, the predominant slip system in Fe{sub 3}Al has been established to be [110] , which provides more than five independent slip systems required for extensive polycrystalline ductility. Recent studies have discovered that the limited ductility is largely the result of environmental embrittlement. Tensile elongation of specimens in air or water vapor is significantly less than those of specimens tested in vacuum or dry oxygen. The low ductility obtained in air tests was ascribed to environmental embrittlement involving hydrogen generated from the reaction of aluminum atoms in the alloy with water vapor. The results of the present work show that the surface coating on the specimens of Fe{sub 3}Al-based alloys can be an effective barrier to reaction with water vapormore » so that the room temperature ductility has been improved significantly.« less

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