Icosahedral-Cluster-Reinforced Structures in Irradiated Metallic Materials

Abstract

A nonequilibrium state has been discovered which is induced by ion irradiation in metallic materials (solid solutions of Fe–Ni, Fe–Cr–Ni, Ni–Cr, Cu–Ni, Fe–Cr, and V–Ti–Cr systems and in pure metals Zr and Ti) at high levels of radiation damage, and the features of this state are considered. In the region of existence of this state, both the ion and the electron subsystems of the metal show highly anomalous properties. Moreover, the occurrence of this state is accompanied by substantial diffraction effects – X-ray line splitting – and, as indicated by electron microscopy, by the formation of a cluster structure. Simulation by the methods of molecular dynamics suggests that the clusters observed are atomic groups of icosahedral (quintuple) symmetry formed in the neighborhood of radiation vacancies. These clusters reinforce the matrix, and this should result in substantial changes in strength and electronic properties of the material. The results of the computer simulation agree with the observed diffraction effects.