MODELING THE EFFECT OF CREEP ON THE GROWTH OF HELIUM BUBBLES IN METALS DURING ANNEALING

The kinetics of helium bubble growth during annealing of unstressed an d stressed metals is modeled. Growth in the matrix, on grain boundarie s as well as on triple grain junctions is considered. A coalescence mo del is developed for the description of helium bubble growth by volume and surface diffusion. The dependence of growth on the location of th e bubbles in the microtructure is discussed. An applied tensile stress has been observed to accelerate bubble growth on grain boundaries and on triple grain junctions [1]. A theoretical model of the influence o f stress-induced grain boundary sliding on bubble growth on triple gra in junctions in a stressed metal due to bubble sweeping by moving disl ocations during creep is suggested. The time-dependent bubble size dis tribution function is discussed for different mechanisms and paths of bubble migration. The time dependences of the number density and mean radius of bubbles in unstressed metal is derived. The present theoreti cal model is compared with experimental TEM results for an Fe-17Cr-17N i alloy which was cyclotron-injected with 160 appm helium and annealed at 1023 K for times up to 1.74 Ms (482 h), due to Braski [J. Nucl. Ma ter. 83 (1979) 265].