INTERNAL MISMATCH STRESSES IN NICKEL-BASED SUPERALLOYS - A FINITE-ELEMENT APPROACH

A three-dimensional finite element (F.E.) model is used to estimate th e mismatch stresses at a microscopic scale in gamma-gamma' single-crys tal nickel-based superalloys. F.E. calculations point out the specific ity of stress/strain distributions in these alloys, in particular the fact that internal stresses concentrate in the connected gamma matrix. The analysis of stress/strain fields and elastic energy evolution as a function of precipitate morphology and volume fraction allows to exp lain some atypical precipitate shape changes such as ''splitting'' dur ing precipitation treatments or ''raftening'' during high temperature creep tests.