MIGRATION OF VACANCIES IN STAINLESS-STEEL MEASURED BY POSITRON-ANNIHILATION

The results of Doppler broadening studies of annealing processes in th e commercial stainless steel are presented. Two stages were establishe d in the temperature dependence of the S-parameter. The first one corr esponds to the steep decrease of the S-parameter in the temperature ra nge from room temperature up to 500-degrees-C and reflects annealing o f defects introduced during the manufacture process. Three models of v acancy sinking and migration were considered. Taking into account diff usion of vacancies to the surface as well as to the grain boundaries g ave the activation energy of vacancy diffusion equal to 1.215 +/- 0.01 6 eV. The increase and consequent decrease of the S-parameter in the t emperature range from 600-degrees-C up to 1060-degrees-C in the second stage is considered as caused by the precipitation of the carbide M23 C6.