Effects of radiation damage and precipitate distribution on micro-pillar compression testing of irradiated CuCrZr

•Micro-pillar testing carried out on CuCrZr with and without irradiation defects.•Intrinsic and extrinsic size effects obvious only in unirradiated CuCrZr.•Size-independent results obtained from smaller pillars following irradiation.•DBH and BKS models predict hardening using microstructural length-scales. [Display omitted] The results of small-scale mechanical tests are convoluted by the so-called size effect, whereby materials appear stronger when the scale of the test is reduced to the order of microns or less. The dimensional range over which this occurs has been shown to be linked to a change in sample microstructure, such as the addition of defects induced by irradiation. To investigate this response, a CuCrZr alloy was subjected to proton irradiation and mechanically tested using micro compression of pillars with a range in size. It was found that irradiation defects dominate over the extrinsic size effect and the sensitivity to differences in precipitate microstructure was also somewhat reduced, suggesting that size-independent results could be obtained from much smaller test volumes in irradiated material compared to their non-irradiated counterparts. Finally, comparison was made between the increase in yield strength predicted by models and the experimentally measured values to establish the key parameters driving the strengthening behaviour.