Revealing hidden defects through stored energy measurements of radiation damage

With full knowledge of a material's structure, it is possible to predict any macroscopic property of interest. In practice, this is hindered by limitations of the chosen characterisation technique. For radiation damage in metals, the smallest and most numerous defects are below the resolution limit of transmission electron microscopy (TEM). Instead of spatial characterisation, we propose to detect defects through their excess energy. Differential scanning calorimetry (DSC) measurements of neutron-irradiated Ti reveal two energetically-distinct processes during stage V annealing. Molecular dynamics (MD) simulations reveal the defects responsible, and show that the point defect-induced glide of dislocation loops contributes significantly to recovery. Our DSC experiments measure defect densities 3 times greater than that determined using TEM. Accurately characterising these 'hidden' defects is crucial to understanding mechanisms at higher length scales, and will advance us towards the ultimate goal in materials science: the deterministic relationship between atomistic structure and macroscopic properties.