Defect evolution in steels: insights from positron studies

Positron annihilation studies on austentic and ferritic/martensitic and oxide-dispersion steels are highlighted so as to emphasize the sensitivity of the technique to defect annealing as well as precipitates. The results obtained on austenitic D9 steels are discussed with a view to emphasize the role of small TiC precipitates in the matrix, which play a critical role in void-swelling behaviour. Further, the role of Ti/C ratio as well as minor alloying elements on swelling behaviour is discussed. The current focus of research is on the use of nanoclusters in ODS alloys towards the suppression of void formation under irradiation. Recent results on the investigation on nano Yttria particles in Fe-model oxide dispersion ferritic steel, are presented with supporting Ab-initio lifetime calculations