Effect of elastic stress field near grain boundaries on the radiation induced segregation in binary alloys

Abstract

An important problem of radiation resistance of structural materials for reactors (different types of steels, including steels doping by low radio-active elements) is their phase stability under neutron irradiation which is associated with the formation of solute radiation induced segregation (RIS) near grain boundaries. The diffusion of alloying elements under irradiation due to interstitial and vacancy diffusion mechanisms towards grain boundaries, which are perfect sinks for point defects results in the RIS formation near grain boundaries. Each grain boundary has the effective elastic stress field produced by the microstructure of grain boundaries. This elastic field can affect the formation of RIS in the dependence on an irradiation dose due to accumulation of impurity elements, gas atoms (helium), formation on grain boundary helium bubbles and precipitates especially at high doses of irradiation. The precipitates and overpressurised helium bubbles are the sources of internal stress fields too and they can dramatically change the effective stress field near grain boundaries. It will result in the redistribution of alloying elements near grain boundaries due to the additional diffusion driving force which is determined by the interaction energy of point defects with effective stress field near grain boundary.