PROGRESS OF SOLID--STATE REACTION AND GLASS FORMATION IN MECHANICALLY ALLOYED Zr_65Al_7.5Cu_17.5Ni_10

摘要

The progress of amorphization in mechanically alloyed Zr_65Al_7.5Cu_17.5Ni_10 powder was investigated in detail using x--ray diffraction, Rietveid analysis, magnetic measurements, metallography, as well as scanning and transmission electron microscopy. For this purpose mixtures of elemental powders were used as starting materials and milled for distinct periods of time. Detailed investigations of the microsimctural evolution during milling indicate that the amorphization proceeds by solid--state reaction, similar to what is known for mechanical alloying of binary alloy systems and other multicomponent alloys. A layered structure typical for mechanically alloyed material arises in the early stages. Alloying of the lamellae, which consist of pure elements, proceeds to some extent via anomalous fast diffusion of small--sized atoms. Besides this, the larger atoms also contribute to alIoying. The observed reaction paths are compared with well--known models describing the amorphization by solid-state reaction in binary systems, suggesting that dislocation pipe diffusion plays a decisive role for intermixing the elements and promoting amorPhization.