Nanocrystallization in driven amorphous materials

Abstract

The nanocrystallization of mechanically milled amorphous alloys was examined both experimentally and theoretically. Mechanical milling induces the precipitation of nanocrystals in an initially amorphous Nd-Fe-B magnetic alloy. The effects of milling speed and duration on precipitate growth/size were investigated. Milling intensity was found to significantly affect the steady-state precipitate size. Precipitate growth kinetics and steady-state precipitate size were governed by a dynamic equilibrium between defect-enhanced diffusional precipitate growth and impact-induced crystal attrition. A linear decrease in steady-state precipitate size with increasing milling speed was predicted, consistent with our experimental data. Nanocrystallization in many driven amorphous alloys can be understood using the kinetic model developed here. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.