MECHANICAL AMORPHIZATION IN THE NI-ZR SYSTEM INVESTIGATED BY POSITRONLIFETIME SPECTROSCOPY

The process of solid-state amorphization induced by high-energy ball m illing of binary mixture of crystalline elemental powders is investiga ted by positron lifetime spectroscopy along with X-ray diffraction and differential scanning calorimetry. The experiments are performed on c ompacted samples of powders mechanically alloyed over a wide compositi on range (state range) at different milling times (state times) and in tensities. The positron lifetime spectra is decomposed into two compon ents. The short-lived component is composition and milling-time depend ent. The second lifetime component, found during the initial stages of the milling process, appears to be due to annihilation from states tr apped at crystalline interface joints. The results indicate that the s olid-state reactions during ball milling involve the transformation an d disappearance of the crystalline interface joints in the powder part icles.