Thermal stability and the structure of vacancy-solute clusters in iron alloys

Thermal stability and the structure of clusters formed by neutron irradiation are studied by means of positron annihilation spectroscopy of post-irradiation annealed FeCu, FeCuMnNi and FeMnNi alloys and rigid lattice calculations. While most of the vacancy-solute clusters dissolve in the temperature range between 650 K and 700 K, the presence of Ni and Mn solutes in vacancy-MnNi clusters provides an additional thermal stability and shifts the annealing stage corresponding to the dissociation of these clusters to higher temperature. Very good agreement between the measurements and calculations is obtained for vacancy-MnNi clusters of nanometric size, containing of about 25-50% of vacancies.