A mechanistic study of Ag50Cu50 solid solution formation by mechanical alloying

This work investigates the phase-transformation kinetics of Ag50Cu50 powder mixtures subjected to mechanical processing by ball-milling. A gradual dissolution of Ag and Cu into each other and the subsequent formation of crystalline metastable solid solutions were observed. A quantitative analysis of X-ray diffraction patterns was carried out to reconstruct kinetic curves. Based on a series of experimental evidences, a phenomenological kinetic model was developed to interpolate experimental data by means of mathematical functions. This allowed the fraction of powder trapped in individual collisions to be estimated and to show that only approximately 5% is involved in reactive events. Local dissolution processes determine the formation of the Ag89Cu11 and Ag12Cu88 metastable solid solutions already at the first impact. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.