Kinetics of allotropic phase transformation in cobalt powders undergoing mechanical processing

The allotropic transition of hexagonal close-packed cobalt powders to the face-centered cubic phase under mechanical treatment conditions has been studied. Processing parameters have been systematically changed to investigate the phase transformation kinetics, which has been related to the number and the average energy of collisions. A phenomenological interpretation of transformation rate constants is also proposed. A minimum threshold energy at impact exists below which no phase transformation is detected.