A Model for the Embrittlement and Annealing of Irradiated Steel

Irradiation of A-302-B steel has been performed for fast-neutron fluences up to 10²¹ n/cm² (E > 500 keV). Charpy impact and hardness results point to a parallel evolution of these mechanical property values. On a semilogarithmic graph an increase in slope by a factor of 4 is observed between 3 and 5 × 10¹⁹ n/cm². At 8.5 × 10²⁰ n/cm², increases in ductile-brittle transition temperature and in hardness were 305°C and 160 kg/mm², respectively. Subsequent annealing treatments between 400 and 500°C indicate that major recovery can be attained. An explanation of the embrittlement and recovery evolution, based on the Davidenkov criterion, is developed.