Deformation-assisted decomposition of unstable Fe50Cu50 solid solution during low-energy ball milling

An unstable, fc.c. Fe50Cu50 solid solution was prepared using high-energy b all milling of an elemental powder mixture. It was used as a parent alloy f or isothermal annealing or low-energy ball milling (LEBM), both at 373-523 K. Alloy evolution was analyzed by X-ray diffraction, Mossbauer spectroscop y and differential scanning calorimetry. LEBM significantly enhanced the in itial decomposition rate, but the decomposition process was complex and not monotonic. At and below 423 K, the initial decomposition was completely re versed at later times. The results are interpreted in terms of an effective -temperature model proposed by Martin for irradiated alloys. A dynamic phas e diagram in the effective temperature is presented, and used to explain th e presence of a two-phase region under all milling conditions. The nonmonot onic behavior is suggested to be a result of coupling between phase evoluti on and mechanical properties, leading to a time dependence of the effective temperature. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Science Ltd. AN rights reserved.