Radiation and helium effects on microstructures, nano-indentation properties and deformation behavior in ferrous alloys

Accelerated ion irradiation, especially 'dual-beam' irradiation, is a useful technique for experimental exploration of irradiation effects and validation of irradiation effect models, because of the unique controllability in irradiation conditions including the helium production rate. In this work, the effects of irradiation and helium implantation on microstructural evolution, hardness and plastic deformation behavior in Fe-15Cr-20Ni model austenitic ternary alloy and Fe-8 ∼ 9Cr-2W reduced-activation martensitic steels were studied through combined applications of ion irradiation, nano-indentation, focused ion-beam microprocessing and transmission electron microscopy. Systematic data on irradiation hardening are presented for broad irradiation conditions. Influences of helium implantation on irradiation-induced microstructural and nano-indentation hardness changes were not detected in the Fe-8 ∼ 9Cr-2W steels, while they were significant in the Fe-15Cr-20Ni alloy. The interaction behavior of dislocation loops with moving dislocations and the strength of the loops as obstacles to dislocation motion are also discussed for these two material classes based on the hardness, and the irradiated and indented microstructures.