One-dimensional motion of interstitial clusters in iron-based binary alloys observed using a high-voltage electron microscope

Systematic experiments on one-dimensional (1D) motion of interstitial clusters in iron-based binary alloys were performed by in situ observation with a high-voltage electron microscope to investigate the effects of atomic size factor of solutes on 1D motion. The respective solute elements and their atomic volume size factors were copper (+17.53%), germanium (+16.48%), and silicon (−7.88%). The solute element concentrations were 52–9100 appm. 1D motion frequency and distance were measured under electron irradiation at room temperature. Addition of copper or silicon of approximately 50 appm reduced the 1D motion frequency and distance. Silicon decreased the 1D motion frequency more strongly than copper. The 1D motion frequency and distance were reduced further with increasing solute concentration, but after several 100 appm, they became insensitive to it. Results for the dilute alloys were examined assuming a model by which individual solute atoms trap interstitial clusters and suppress their 1D motion.