Comments on “The absence of a stable hexagonal Laves phase modification (NbCr2) in the Nb–Cr system”

Recently, Aufrecht et al. (Scripta Mater. 62 (2010) 227) published a paper investigating the previously proposed polytypic phase transformation C14 NbCr2 to C15 NbCr2. In their analysis, they considered that the phase transformation does not occur for high-purity alloys, and the conditions and small amounts of atmospheric contaminations induce the formation of an η-carbide-type phase. However, I point out here that previous experimental results do not agree well with their analysis. Aufrecht et al. also do not adequately acknowledge earlier work on this topic, and their experiments are not strict enough.