Dependence of proton irradiated microstructure on dose, temperature and composition of austenitic stainless steels

The radiation-induced microstructure of austenitic stainless steel was investigated using proton irradiation. Samples of Fe-20Cr-24Ni and Ni-18Cr-9Fe were irradiated using 3.2 MeV protons at a dose rate of 7×10^-6 dpa/s between 300 °C and 600 °C. The irradiation produced a microstructure consisting of dislocation loops and voids in both alloys. The number density and size of dislocation loops and voids are strong functions of irradiation temperature with the number density decreasing and the size increasing with temperature for both defects. The dose dependence of dislocation loop density saturated around 1.0 dpa for Fe-20Cr-24Ni and 0.3 dpa for Ni-18Cr-9Fe. The microstructure evolution in the nickel base alloy is faster than that in Fe-20Cr-24Ni. The dose and temperature dependence of proton irradiated Fe-20Cr-24Ni closely follow that of neutron irradiated austenitic stainless steels. The changes in yield strength due to irradiation were estimated from nano indenter hardness measurements and compared to calculation using a dispersed barrier hardening model. Results were in close agreement with each other. Yield strength changes as a function of dose for proton irradiated Fe-20Cr-24Ni are similar to those resulting from neutron irradiation of austenitic stainless steels.