Amorphization of Interstitial Elements Containing Iron Materials by Mechanical Alloying

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In mechanical alloying (MA) of Fe–C and Fe–N materials with additive elements A such as Nb, Ti, Cr, and Co in an Ar atmosphere using a ball mill, the amorphization of MA powders is most crucially dependent on the interaction parameter WAX (X=C or N) among the several properties of additives A, including their melting points and atomic sizes, and the milling energy supplied to MA materials. The parameter WAX represents the difference between the bonding energies of the atomic A–X pair (UAX) and the Fe–X pair (UFeX) in the Fe–A–X solution, i.e., WAX=UAX-UFeX. Additives such as Cr and Nb with negative WAX values markedly promote the amorphization of MA materials, in contrast to Co or Ni which have positive WAX values. When V–VI group elements with negative and moderate WAX values, such as Nb, Ta, and Cr, are employed as the ternary additives, the amorphization of Fe–C and Fe–N materials is readily attained.