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With full knowledge of a material’s atomistic structure, it is possible to predict any macroscopic property of interest. In practice, this is hindered by limitations of the chosen characterization techniques. For example, electron microscopy is unable to detect the smallest and most numerous defects in irradiated materials. Instead of spatial characterization, we propose to detect and quantify defects through their excess energy. Differential scanning calorimetry of irradiated Ti measures defect densities five times greater than those determined using transmission electron microscopy. Our experiments also reveal two energetically distinct processes where the established annealing model predicts one. Molecular dynamics simulations discover the defects responsible and inform a new mechanism for the recovery of irradiation-induced defects. The combination of annealing experiments and simulations can reveal defects hidden to other characterization techniques and has the potential to uncover new mechanisms behind the evolution of defects in materials. 

Radiation damage in structural materials for nuclear applications is not well-understood, especially when linking the atomic scale damage mechanisms to the macroscopic effects. On a microscopic level, particle radiation creates defects that can accumulate in the material. Defects can also interact with existing features in the material. Since both defects and features have different energies associated with them, investigation of the resulting energy spectrum in a macroscopic sample may offer insight into the connection between microscopic damage and macroscopic properties. In alloys, changes in the size and number of precipitates will be reflected in the amount of energy required to dissolve the precipitates during thermal analysis. This can then be studied using differential scanning calorimetry (DSC). This work explores the sensitivity of the DSC measurement to detect irradiation-induced instability in metastable and secondary phase precipitates in the high-strength aluminum alloy 7075-T6 for extremely low doses of helium-ion and neutron irradiation. The precipitates in aluminum 7075-T6 are expected to grow or shrink, changing the energy spectrum measured by DSC. The magnitude of the change can then be compared to a model of irradiation-induced phase instability. This will demonstrate the ability of this thermal analysis technique to help bridge the gap between microscopic radiation effects and macroscopic properties.