Story of stacking fault tetrahedra

Abstract

Stacking fault tetrahedra, although they have a peculiar structure, are the most general type of vacancy clustered defects in f.c.c. metals and alloys. Placing these stacking fault tetrahedra at the center, the story of point defect reaction is told. The structure of the defect and the energy relation are first described. Various experimental treatments which lead to the formation of stacking fault tetrahedra are described, featuring characteristic point defect processes in each. Quenching from high temperature leads to an understanding of the nucleation processes. Electron irradiation focuses on the relation with the local accumulation of vacancies, and the stochasticity of point defect reaction is detected in terms of the behavior of the defects during irradiation. Microstructural evolution by irradiation with neutrons and ions is well illustrated by the formation of stacking fault tetrahedra directly from collision cascades. Subcascade formation, estimation of deposited energy density, impact effect from cascade collision to point defect reaction, and roles of freely migrating point defects are included in the story related to the formation of stacking fault tetrahedra. Finally, plastic deformation, especially recent results on high-speed heavy deformation, presents the striking result of the formation of high density stacking fault tetrahedra even in pure aluminum, which leads to a proposal of plastic deformation without dislocation.