Influence of carbon upon the development of the gas porosity of nickel saturated with helium up to 10-2 atomic percent during annealing at 500--1000 degrees C

The radiation stability of materials depends to a significant extent upon the base of the alloy and the presence of alloying elements; implanted admixtures such as carbon, nitrogen, boron, phosphor, etc., are very important. Despite the greatly inconsistent data on the influence of implanted admixtures upon the development of pores and upon swelling, many researchers assume that admixtures which are present in a solid solution will reduce the swelling because the incubation period of core development is increased. When implanted admixtures precipitate as secondary phases (coarse carbides, borides, carbonitrides, etc.) from a solid solution, swelling is enhanced because the solid solution is depleted of alloying elements and coarse pores form on the interface of the precipitate with the matrix. Helium, which is always present in reactor materials, plays an important role in pore formation processes. The influence of carbon on the helium-induced porosity has been studied very little. In order to clarify the importance of carbon in the development of gas porosity, the structure of Ni-C alloys, which had been irradiated with 29 MeV helium ions and annealed after the irradiation at 500-1,000 degrees C, was studied under an electron microscope. Nickel and its alloys with carbon were chosen for the study because nickel is one of the most thoroughly studied metals with a face-centered cubic crystal lattice and serves as a model material in many experiments, whereas carbon forms a component of most steel brands and alloys