PHASE INSTABILITY UNDER CASCADE DAMAGE IRRADIATION

Displacement cascades have a much greater power to disrupt the crystal line lattice than do single displacement events. The effects of displa cement cascades on particle resolution, on disordering, and on amorphi zation are considered herein. Particle resolution is found to be a rel atively slow process, even with the assistance of displacement cascade s. Larger displacement cascades which give greater recoil distances ar e found to give faster resolution. Numerous experimental studies of ox ide particles in metallic matrices have revealed at most the first sta ges of radiation recoil dissolution. Ordered intermetallic compounds a re readily disordered by low temperature irradiation, even in the abse nce of displacement cascades. It was recently shown theoretically that displacement cascades may give disordering when equivalent displaceme nt conditions without cascades leave the alloy ordered. Radiation amor phization of intermetallic compounds has been observed under a variety of irradiation conditions. Some compounds amorphize readily under cas cade-inducing heavy ion irradiation but not under electron irradiation . Recent modelling. studies have shown that clusters of defects, such as may be formed in cascades, may be needed for amorphization.