RELATION BETWEEN STRUCTURAL-PROPERTIES AN D MORPHOLOGY OF GAMMA' PRECIPITATES OF AN AM1 NICKEL SINGLE-CRYSTAL SUPERALLOY

Measurements of the distortion of the lattice cells and of the lattice parameter mismatch between the gamma and gamma' phases of two AMI sin gle crystal superalloy samples with different morphology of the precip itates are reported as a function of temperature. They show that these quantities are strongly influenced by the shape and the size of the p recipitates and are not intrinsic properties of the alloy. The dilatat ion of each phase is deduced from the study of the crept sample and al lows to propose a scheme for the evolution of the lattice parameter of the heat-treated sample. In particular a cross over from an elastic a ccommodation to a plastic relaxation is evidenced.