Sample size effect phenomenon in microcompression testing of unirradiated and ion-irradiated 800H steel at high temperatures

Abstract

In situ microcompression testing is used to quantify the mechanical properties of materials and directly observe the deformation mode. It allows to be site specific and probe specific microstructural regions of interest. Sample size effect, where the strength of materials increases with decreasing sample size, remains a challenge. This phenomenon has been studied widely at room temperature but not at elevated temperature. This work here sets out to evaluate and understand the scaling effects at elevated temperature on irradiated and unirradiated austenitic (FCC) Fe-Cr-Ni alloy 800H. Micro-compression samples were fabricated in a 〈111〉 grain containing both the unirradiated and the irradiated volumes for direct comparisons of yield strength at room temperature and 300 °C. TEM lift-out of the compressed micro-pillars at room temperature were fabricated for microstructural characterization. The influence of irradiation and temperature on sample size effect are independently investigated. It was observed that sample size effects increased with increasing temperature in only the unirradiated material.