Influence of Fe and Cr on the disordering behavior of mechanically alloyed NiAl

Abstract

The role of Fe and Cr on the disordering behavior of mechanically alloyed nanocrystalline NiAl has been investigated. The results of milling with WC media show that NiAl is only partially ordered in the as-milled stoichiometric composition. Addition of 20 at.% of Fe or Cr results in a completely disordered NiAl structure. The change in the long range order parameter with increase in Fe or Cr is insignificant up to 8 at.%, and then it decreases rapidly to zero at concentrations higher than 16 at.%. The deformation induced defects introduced by high energy ball milling seem to contribute significantly to the disorder. Large amount of Fe contamination (~18 at.%)from stainless steel milling media has also caused complete disorder in NiAl. Contamination from steel milling media may, therefore, be useful to ductilize the otherwise brittle aluminides through the introduction of disorder.