Quantifying the mechanical degradation of structural materials for nuclear fission and fusion applications, owing to their exposure to energetic particles, requires a detailed and accurate analysis of the interactions between gliding dislocations and nanoscale radiation defects, such as prismatic dislocation loops. This study presents the first direct experimental examination of individual dislocation–loop interactions in body-centered cubic metals under high-temperature deformation. Moreover, it represents the first direct observation of individual interactions between dislocations and any type of nanoscale defect in iron and iron-based alloys during deformation at an elevated temperature. Using in situ transmission electron microscopy, we directly observe the dynamics of the interaction between a gliding 1/2 screw dislocation and a interstitial-type dislocation loop in iron under tensile deformation at room temperature (300 K) and an elevated temperature (840 K). These interactions are classified into five reaction types in terms of the loop transformation. While only two reaction types are observed at 300 K, all five occur at 840 K. Crucially, the resistance offered by a loop to dislocation glide is higher at the elevated temperature, contradicting the traditional notion of obstacle strength, which assumes that such resistance by defects and precipitates to dislocation glide decreases with increasing temperature. Thermal fluctuations play an inherent role in the selection of the dislocation reaction type and underlie the stochastic nature of the resistance offered by a loop to dislocation glide.
Inoue et al. (Sun,) studied this question.