Abstract
Radiation-induced changes in microstructure and mechanical properties in structural materials
are the result of a complex set of physical processes initiated by the collision between an
energetic particle (neutron or ion) and an atom in the lattice. This primary damage event is called
an atomic displacement cascade. The simplest description of a displacement cascade is to view
it as a series of many billiard-ball-like elastic collisions among the atoms in the material. This
chapter describes the formation and evolution of this primary radiation damage mechanism to
provide an overview of how stable defects are formed by displacement cascades, as well as the
nature and morphology of the defects themselves. The impact of the relevant variables such as
cascade energy and irradiation temperature is discussed, and defect formation in different
materials is compared.
