THE INFLUENCE OF SYNCHROTRON-RADIATION-INDUCED STRAIN ON THE GROWTH AND DISSOLUTION OF BRITTLE AND DUCTILE MATERIALS

Sodium chlorate (brittle) and sodium nitrate (ductile) crystals were i rradiated by synchrotron radiation to produce samples in which one-hal f of a particular crystal was strained by radiation damage and the oth er not. The growth and dissolution kinetics of these samples were inve stigated using in situ laser interferometry and X-ray topography. An a ppreciable difference was observed in the growth and dissolution kinet ics of the irradiated and nonirradiated halves. In the region of very low supersaturation, sigma < sigma(c) = 0.32% for sodium chlorate and sigma < sigma(c) = 0.065% for sodium nitrate, the irradiated portions of both types of crystals dissolved; simultaneously, the nonirradiated portions grew. Above the critical supersaturation, sigma(c), both hal ves grew. This defines a difference in solubility between the irradiat ed and nonirradiated material. The significant difference between the two critical supersaturations in the two materials confirms our earlie r findings that a larger amount of elastic strain per unit volume can be introduced into brittle materials than into ductile ones. This, in turn, has a much stronger effect on both growth and dissolution kineti cs. Irradiation is shown to yield pure point defect strain and not to introduce dislocations in the system. A possible mechanism by which st rain influences the growth and dissolution kinetics is discussed.