Statistical in situ scanning electron microscopy investigation on the failure of oxide scales

Oxide scales play a pivotal role in obstructing surface chemical and electrochemical reactions, hence hindering chemo-mechanical effects such as liquid metal embrittlement of steels. Therefore, the critical conditions and failure mechanism of the oxide film are of major interest in the safe service of steels. Though in situ microscopic methods may directly visualize the failure mechanism, they are often challenged by the lack of statistically reliable evaluation of the critical conditions. Here, by combining in situ scanning electron microscopy with a tapered specimen tensile test in a single experiment, we uniquely achieve a mechanistic study with statistically reliable quantification of the critical strains for each step of the dynamic process of film rupture. This is demonstrated with the oxide films formed on a ferrite–martensite steel in liquid lead–bismuth eutectic alloy at elevated temperatures, with in situ results falling right into the predictions of the statistical analysis. Explicitly, the integrated experimental methodology may facilitate the materials genome engineering of steels with superior service performance.