A great interest in nanocrystalline materials (nmaterials) stems from anticipation that their properties will be different from, and hopefully superior to, those of conventional materials. In particular, it is already well known that n-metals exhibit greater microhardness values than their coarse-grained counterparts and that the ambient temperature ductility of n-metals is significantly reduced. On the other hand, n-ceramics exhibit both increased hardness and some ductility. On another note, intermetallic materials are of potential use for aerospace applications. However, conventionally processed intermetallics suffer from ambient temperature brittleness. One of the intermetallics, which is being considered as a potential low-density aerofoil material, is NiAl. NiAl is an intermetallic compound with the B2 ordered structure exhibiting high melting point, high strength-to-weight ratio, good thermal conductivity and excellent oxidation resistance. Like other intermetallics, though, it lacks ambient temperature ductility [1]. In light of the demonstrated ductility in the nanocrystalline range of otherwise brittle ceramics, the interest in NiAl intermetallics, and the necessity to address its low temperature brittleness (if this material is to demonstrate its structural potential), a research study was conducted on n-NiAl by a group led by one of the co-authors and its results were published (see e.g., [2]). The present contribution is aimed at rationalizing the mechanical behavior of the material based on the current understanding of diffusional and dislocation phenomena in nmaterials.
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