Irradiation-induced vacancy and Cu aggregations in Fe-Cu model alloys of reactor pressure vessel steels: State-of-the-art positron annihilation spectroscopy

Theoretical and experimental aspects of positron annihilation studies of precipitate-relevant phenomena in Fe-Cu model alloys of reactor pressure vessel steels are discussed. Although the positrons are thought, in general, to be insensitive to the impurities in solids, we demonstrate that the positrons can be confined as a quantum-dot state within the nano Cu or Cu-rich precipitates in the Fe-Cu model alloys, which makes the positron annihilation one of the most promising techniques in this field. The positron probe is employed successfully to clarify that nano Cu precipitate has a bcc structure coherent with the Fe matrix. The results show clearly that the quantum-dot-state positrons exclusively detect the microscopic and electronic structures of the precipitates.