Incipient chemical instabilities of nanophase Fe-Cu alloys prepared by mechanical alloying
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the importance of the grain-boundary energy in the alI.
INTRODUCTION
M E C H A N I C A L alloying has been used to synthesize alloys that are far from thermodynamic equilibrium in their constituent phases,tl-sI grain sizes, [6'7] and chemical compositions.iS ~l Alloys prepared by mechanical alloying are, therefore, expected to be unstable against phase transformations, grain growth, and chemical ordering or segregation. In the present investigation, we studied the early stage instabilities of Fe-Cu alloys prepared by mechanically alloying. Previous studies of mechanically alloyed Fe-Cu showed it is possible to obtain crystallite sizes on the order of 10 nm and to extend dramatically the solid solubilities of both the face-centered cubic (fcc) and body-centered cubic (bcc) phases. The solubility of Cu in the bcc phase was found to be at least 20 pct, and the solubility of Fe in the fcc phase was found to be at least 60 pct, [12
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