Publications

Abstract : The void swelling behaviour of (15Ni-14Cr)-O.25Ti and (15Ni-14Cr)-O.15Ti steels are studied using heavy ion irradiation for understanding the influence of titanium in the void swelling resistance of these D9 alloys. The cold worked samples have been pre-implanted with a uniform helium concentration of 30 appm spanning a width of about 640 nm. This was followed by a 5-MeV nickel ion irradiation to create a peak damage of ∼ 100 dpa at a damage rate of 7 x 10-3 dpa/s at various irradiation temperatures between 700 and 970 K. The gross swelling in the implanted range is measured by step height measurements. It is found that the peak swelling temperatures and the magnitude of swelling for the alloys are different. The difference in void swelling behaviour with variation in titanium concentration in these two alloys is discussed on the basis of the role of titanium on the vacancy migration and TiC precipitate formation. Isochronal annealing study of the positron lifetime in the un-irradiated alloys reveals different TiC precipitates formation behaviour in the two alloys. Ab initio calculations of positron lifetime, using large super-cells, show that C vacancies at the TiC/austenite interface are the predominant positron trapping centres in these alloys.