Ion implantation, ion beam mixing, and ion beam stimulated reactions can be discussed as somewhat distinct but related processes. The first two emphasize compositional changes in near-surface regions. The last relies mainly on microstructural and precipitation reactions caused by atomic displacements. In this last area much of the work has been carried out in metallic alloys. Here we summarize experiments in our laboratory that cover several ion-beam-induced reactions in Fe-15Ni-15Cr base alloys, to provide a perspective on related work in materials other than silicon. The techniques and mechanistic interpretations of results are applicable to a variety of materials.This is a powerful way to examine the interplay of characteristic relaxation times. Intervals of high point defect production and resultant processes, such as solute segregation and drift-directed clustering, are alternated with thermal annealing. Remarkable changes with respect to either steady bombardment or thermal aging at the same temperature can be produced. Figure 1(a) shows theoretically calculated fluctuating vacancy concentration in a steady irradiation.