Coarsening behaviour of γ″- and γ′-particles in Inconel alloy 718

Abstract

The coarsening behaviour of disc-shaped, ordered bct γ″-phase, and spherical ordered fcc γ′-phase particles in Inconel alloy 718* has been studied. In the 973–1023 K temperature range, used in the present investigation, both the phases are present and precipitate coherently in the fcc matrix. The coarsening kinetics of both the phases follow the time-law predictions of the Lifshitz–Wagner theory of diffusion-controlled growth at all the aging temperatures. The actual particle size distribution, however, differs significantly from the theoretically predicted distribution which could be attributed to the effect of ‘encounter’ between the growing particles and could also be due to a large lattice misfit between the precipitate and the matrix.