Lattice Defects and Plastic Deformation of CoSi2

Abstract

Current knowledge of the properties of vacancies and the slip behavior and mechanisms of CoSi2 is reviewed based on the results of our recent studies on CoSi₂. The concentration of thermal vacancies in CoSi₂ is much higher than that in ordinary metals and alloys with melting points comparable with that of CoSi₂. Vacancy defects are easily retained in CoSi₂ even after air cooling from high temperatures. An annealing stage observed at around 310 K after electron irradiation is concluded to occur by the migration of vacancies to form secondary defects. Peculiar phenomena recently reported on CoSi₂ such as an anisotropy of electrical resistivity and the climbing of dislocations at room temperature can be understood on the basis of the current knowledge of defect properties. Slip in CoSi₂ occurs along <100> on {001} at low temperatures. The selection of {001}<100> as the primary slip system in CoSi₂ can be interpreted in terms of high covalency of Co-Si bonding. a<100> dislocations have a strong tendency to align along their edge orientation and are dissociated into two a / 2<100> partial dislocations separated by a stacking fault on {001}. {001}<100> slip is augmented by {111}<110> and {110}<110> slip at high temperatures. Thermal activation analysis of deformation indicates that while deformation at low temperatures is controlled by the Peierls mechanism, the greatly increased concentration of thermal vacancies influence the mobility of dislocations at high temperatures.