Methods of analysis and measurement of irradiation creep in non-cubic metals

Irradiation creep and growth in non-cubic metals causes anisotropic dimensi onal changes relative to the crystallographic axis in each individual grain . Since the deformation of each grain is constrained by the collective defo rmation of neighbouring grains, anisotropic deformation generates internal stresses due to interganular interaction. These must be taken into account to represent and interpret correctly the creep behaviour of polycrystalline samples. In this paper, models of irradiation creep in non-cubic single cr ystals are considered and a self-consistent analysis to relate the creep be haviour of single crystals to that of the polycrystals is described. Severa l methods to extract single-crystal behaviour from polycrystalline data are suggested and the application to Zr-2.5Nb alloy is illustrated.