Annealing response of point defects in off-stoichiometric Mo5SiB2 phase

Dislocations and planar faults are found to develop in the Mo5SiB2 phase during elevated temperature annealing. The dislocations formed in Mo5SiB2 of annealed alloys are mostly edge dislocations with the Burgers vectors of 〈100], 1/2〈111], and 〈110]. For the Mo-rich Mo5SiB2 phase that formed in a Mo-10Si-20B alloy, a significant amount of constitutional vacancies is introduced during solidification, and the excess vacancies aggregate and collapse into dislocations. At the same time, these dislocations can act as the heterogeneous nucleation sites for the subsequent Mo precipitation. For the Mo-lean Mo5SiB2 phase that formed in a Mo-13Si-28B alloy, the constitutional defects are not significant for the development of dislocations.