Effect of proton irradiation on positron annihilation and micro-Vickers hardness of Fe-C-Cu model alloys

Positron lifetime and micro-Vickers hardness were measured on well annealed model alloys, Fe-C(0%, 0.2%, 0.35%)-Cu(0%, 0.15%, 0.3%), after 1 MeV proton irradiation with a dose of 3 x 1017/cm2 below 80 C. Longer lifetime, ranging from 310 to 360 ps, component appears and gives evidence of formation of microvoids containing about 10 vacancies. The longer lifetime decreases with increasing copper content and suggests smaller microvoids for Fe-Cu alloys. The longer lifetime increases with annealing temperature up to 400 C in pure Fe, but exhibits decrease around 300 C in Fe-C-Cu alloys. This decrease indicates reduction in effective size of microvoid around 350 C. Irradiation hardening is accelerated by copper but retarded by carbon. Post-irradiation anneal hardening is revealed at about 150 C and 350 C in Fe-C and Fe-C-Cu alloys. In Fe-Cu alloys, however, a single narrow hardening peak is observed around 350 C. The irradiation hardening in Fe-C alloy anneals out around 550 C, while that in alloys containing Cu makes complete recovery at about 650 C