Particle Size Distributions During Diffusion Controlled Growth and Coarsening (Preprint)

摘要

The chemical partitioning of alloying elements between the disordered y and ordered y-prime phases in the nickel base superalloy Rene 88DT, has been characterized in detail using three dimensional atom probe tomography (3DAP) coupled with energy-filtered transmission electron microscopy studies. After a homogenization treatment followed by a water quench, it is observed that the morphology of the y-prime precipitates remains near-spherical even after long aging times. Compositional variation, observed between small (less than 5 nanometers) and larger y-prime precipitates, reduces with increasing aging time, while the compositional gradient across the y/y-prime interface decreases. The process of growth of y-prime precipitates seems to occur through coalescence of adjacent y-prime precipitates, facilitated through the formation of 'necks' between adjacent precipitates. These necks are observed to have intermediate elemental concentration values, between the matrix and the y-prime precipitate compositions.