\u3cem\u3eIn Situ\u3c/em\u3e TEM Micropillar Compression Testing in Irradiated Oxide Dispersion Strengthened Alloys

The objective of this study is to determine the validity of in situ transmission electron microscopy (TEM) micro-compression of pillars in as received and ion-irradiated Fe-9%Cr oxide dispersion strengthened (ODS) alloy. The growing role of charged particle irradiation in the evaluation of nuclear reactor candidate materials requires the development of novel methods to assess mechanical properties in near-surface irradiation damage layers just a few micrometers thick. In situ TEM mechanical testing is one such promising method, yet size effects must be understood to validate the technique. In this work, a micro-compression pillar fabrication method is developed. Yield strengths measured directly from TEM in situ compression tests are within expected values, and are consistent with predictions based on the irradiated microstructure. Measured elastic modulus values, once adjusted for deformation and deflection in the base material, are also within the expected range. A pillar size effect is only observed in samples with minimum dimension ≤ 100 nm due to the low inter-obstacle spacing in the as received and irradiated material. By comparing the microstructural obstacle spacing with specimen dimensions, size effects can be understood and TEM in situ micropillar compression tests can be used to quantitatively determine mechanical properties of shallow ion-irradiated layers