Nucleation of (Mo) precipitates on dislocations during annealing of a Mo-rich Mo₅SiB₂ phase

Upon annealing an as-cast Mo-10Si-20B alloy at high temperatures, a Mo solid solution phase precipitates within a supersaturated Mo₅SiB ₂ phase. The precipitation behavior of the Mo solid solution was investigated by means of transmission electron microscopy and X-ray diffractometry. It is found that the Mo₅SiB₂ phase in a Mo-10Si-20B alloy contains a significant amount of structural vacancies in the as-cast state. The excess vacancies are removed to form dislocations during annealing, which provides the heterogeneous nucleation sites for the (Mo) precipitates.