PLEPS study of ion implanted and annealed Fe-11.62%Cr alloys

Abstract

Reduced activation ferritic/martensitic (RAFM) steels are one of the candidate structural materials for application in future nuclear facilities. These steels fulfill demands on radiation, thermal, and mechanical resistance during their operational lifetime. Our experiments were focused on study of microstructural changes of binary Fe-Cr alloys after annealing and irradiation, experimentally simulated by ion implantations. Alloys with 11.62% Cr were examined after helium ion implantations at different doses (0.1; 0.3; 0.5 C/cm2). Thermal annealing, motivated by literature and our previous work in the field of reactor steels [1,2], was performed at temperatures of 400, 475, 525 and 600 °C after implantations with aim to study changes of the defect size/amount. The Pulsed Low Energy Positron System (PLEPS) at FRM II reactor in Garching (Munich) was applied for lifetime studies [3]. Damage introduced into the microstructure caused problems with defect interpretations by the PLEPS technique and therefore SEM was applied as well. Positron lifetimes measured at annealing temperatures in range of 400 – 525 °C did not show an expected decrease. Only in the case of temperature of 600 °C the mean lifetime (MLT) decreased significantly and assumptions about the defect size decrease were made according to the literature [2].