ISOCHRONAL ANNEALING BEHAVIOR OF MECHANICALLY MILLED NANOCRYSTALLINE COPPER-BASED IRON-ALLOYS

Powders of copper, with zero to 50 weight percent iron were mechanical ly milled for 20 hours in a SPEX 8000 high-energy ball mill. The mille d powders were cold pressed into compacts and were isochronally anneal ed in vacuum to 605 degrees C. Room temperature thermal diffusivity an d x-ray diffracting particle sizes were measured as a function of anne aling temperature. The as-pressed specimens had an average diffracting crystallite size of 12 nm and a thermal diffusivity of 0.112 cm(2)/s for copper, which decreased to 0.013 cm(2)/s with the addition of 50% iron. After the five annealing steps, the diffusivity of the copper in creased to 0.745 cm(2)/s while in the copper 50% iron increased to 0.1 46 cm(2)/s. (C) 1997 Acta Metallurgica Inc.