Particle size evolution in Cu-15at% Al mechanically alloyed

Characterization of the particle size in a Cu-15at%Al powder mixture, processed in a low energy mill, was conducted. Milling times included 1.8, 7.2, 28.8, 54, 90, 180, 360, and 864 Ks. A commercial particle size analyzer, based on the sedimentation-photometry technique, was used to obtain particle size distributions according to frequency of number, volume, or area. Equivalent medium diameter for particles as a function of milling time is reported. These results me supported by observations in optical, scanning and transmission electron microscopes. A high number of submicrometric fragments were detected since the early milling times (1.8 Ks up to 180 Ks). This observation could have relevance for the study of the mechanisms of the mechanical alloying and of the nanometric grain size formation. A competition between fragmentation and coalescence events in the particle population has been observed to take place during the complete milling process. (C) 1999 Acta Metallurgica Inc.