In situ microtensile testing for ion beam irradiated materials

Understanding the changes in mechanical properties and failure mechanisms as a function of radiation damage is important for long-term operation of structural components in nuclear reactors. Due to the expense, the activation of the sample, and the long duration of neutron irradiation, ion beam irradiations (proton-irradiation and, increasingly, heavy-ion irradiation) are used as surrogates for neutron irradiation. However, the shallow irradiation depths of ion-beam irradiation have restricted mechanical property measurements until the recent advent of small-scale mechanical testing. In previous studies, nano-hardness and yield strength of proton-irradiated 304SS were measured using nanoindentation and in situ microcompression respectively. This study develops an in situ microtensile testing method to provide direct stress-strain curves, including the strain to failure, which previous studies do not provide. In addition, a novel way of quantifying irradiation-induced susceptibility to slip band formation in microscale specimens was demonstrated. Lastly, the paper introduces a new technique for measuring grain boundary strength, demonstrated on an oxidized grain boundary of Alloy 600 exposed to primary water chemistry environment.