Thermodynamic mechanisms of mechanical crystallization of amorphous Fe-N alloy

Abstract

An amorphous Fe-N alloy is prepared by ball milling a mixture of Fe and hexagonal boron nitride. Its crystallization processes were studied upon mechanical milling and annealing under normal and high pressure. The crystallization product of the amorphous Fe-N alloy induced by mechanical milling and annealing at temperatures between 690 and 800 K under pressures of 3-4 GPa is the ε-FexN phase, while the thermal crystallization product under normal pressure is γ′-Fe4N. The difference in crystallization product between mechanical crystallization and thermal crystallization is attributed to the effects of local pressure and local temperature produced by ball collisions on crystallization of amorphous Fe-N alloy. © 2002 Elsevier Science B.V. All rights reserved.