Simulations of Ti-Y-O Nanoclusters in Ferritic Alloys

Nanostructured ferritic alloys possess high strength and resistance to radiation effects due to the presence of nanoprecipitates. Though nanostructured ferritic alloys have desirable mechanical properties, the exact composition and structure of the nanoprecipitates is unknown; thus, atomistic simulations involving the formation of nanoclusters give insight as to their structure. This thesis focuses on the structure, formation and radiation stability of Ti-Y-O [titanium-yttrium-oxygen] nanoclusters in iron. The activation energies for diffusion and the diffusion coefficients of oxygen interstitial atoms in iron are determined. The binding energies of various combinations of oxygen interstitial atoms and iron vacancies are also tabulated. Thermodynamic formation energies of Y-O and Ti-O nanoclusters are calculated. Also, the effects of radiation on Ti-Y-O clusters are studied using defect cascade simulations. Yttrium and titanium are found to provide stability in small oxygen clusters. Ti-Y-O clusters are found to exhibit resistance to radiation damage. Radiation effects are found to be minimal in instances in which the primary knock-on atom is a yttrium atom near the center or on the periphery of the Ti-Y-O precipitate cluster.