  We present a comprehensive set of first principles electronic structure
calculations to study transition metal solutes and their interactions with
point defects in austenite. Clear trends were observed across the series.
Solute-defect interactions were strongly correlated to the solute size factors,
consistent with local strain field effects. Strong correlations with results in
ferrite show insensitivity to the underlying crystal structure in Fe. Oversized
solutes act as strong traps for vacancy and self-interstitial defects and as
nucleation sites for the development of proto-voids and small self-interstitial
loops. The reduction in defect mobility and net defect concentrations explains
the observed radiation-damage resistance in austenitic steels doped with
oversized solutes. Oversized solutes remaining dissolved in oxide
dispersion-strengthened (ODS) steels could contribute to their radiation-damage
resistance. Ni and Co diffuse more slowly than Fe, along with any vacancy flux
produced under irradiation below a critical temperature, which is 400 K for Co
and their concentrations should be enhanced at defect sinks. Cr and Cu diffuse
more quickly than Fe, against a vacancy flux and will be depleted at defect
sinks. Oversized solutes early in the transition metal series form
highly-stable solute-centred divacancy (SCD) defects with a nearest-neighbour
vacancy. The vacancy-mediated diffusion of these solutes is dominated by the
dissociation and reassociation of the SCDs, with a lower activation energy than
for self-diffusion, which has important implications for the nucleation and
growth of complex oxide nanoparticles containing these solutes in ODS steels.
Interstitial-mediated solute diffusion is energetically disfavoured for all
except Cr, Mn, Co and Ni. The central role that solute size plays in the
results presented here means they should apply to other solvent metals and
alloys.
