Abstract
Clustering in alpha iron‐molybdenum alloys begins with the formation and growth of dislocation rings from supersaturated vacancies. The rings form on {100} planes and reach a maximum diameter of ∼800 A. Segregation of molybdenum to these rings starts just after their formation. Molybdenum‐rich zones grow inside the rings until a disk is formed. After very long periods of aging, particles of the bcc η solid solution form from the clusters at aging temperatures below 500°C.