Amorphization in an immiscible CuTa system by mechanical alloying

Abstract

The amorphization of Cu 30Ta 70 powders by mechanical alloying has been studied. The structural changes in this material during mechanical alloying were monitored by X-ray diffraction and transmission electron microscopy. It was found that a nanocrystalline supersaturated solid solution of tantalum was formed in the initial stage of mechanical alloying. Amorphous transformation of alloyed powders began to take place when the milling time exceed 30 h and a single phase of an amorphous product was obtained after 100 h of milling. The crystallization reaction of the formed amorphous phase was studied by differential thermal analysis and the kinetics of the reaction has been examined as well. The present results suggest that the enhancement of the free energy due to the supersaturation of copper in tantalum and the introduction of a high density of defects by ball milling comprise the driving force for the amorphization of the Cu-Ta system.