DEFORMATION-ASSISTED DECOMPOSITION OF UNSTABLE Fe_50Cu_50 SOLID SOLUTION DURING LOW- ENERGY BALL MILLING

摘要

An unstable, f.c.c. Fe_50Cu_50 solid solution was prepared using high-energy ball milling of an el- emental powder mixture. It was used as a parent alloy for isothermal annealing or low-energy ball milling (LEBM), both at 373-523 K. Alloy evolution was analyzed by X-ray diffraction, M0ssbauer spectroscopy and differential scanning calorimetry. LEBM significantly enhanced the initial decomposition rate, but the decomposition process was complex and not monotonic. At and below 423 K, the initial decomposition was completely reversed at later times. The results are interpreted in terms of an effective-temperature model proposed by Martin for irradiated alloys. A dynamic phase diagram in the effective temperature is presented, and used to explain the presence of a two-phase region under all milling conditions. The non- monotonic behavior is suggested to be a result of coupling between phase evolution and mechanical prop- erties, leading to a time dependence of the effective temperature.