Evolution of size and morphology of γ′ precipitates in UDIMET 720 Li during continuous cooling

Abstract

In this work, an analysis of the evolution of precipitates in the nickel-base superalloy UDIMET 720 Li during continuous cooling is carried out. Starting from the solution-annealed condition, the precipitation kinetics, the distribution and the morphology of particles during continuous cooling is studied experimentally by SEM, EFTEM and FIB. The results are compared to simulations using the software MatCalc. Depending on the cooling rate, discontinuous precipitation as well as monomodal and multi-modal distributions are observed. The precipitate microstructure of various samples is investigated and evaluated quantitatively to determine the precipitate distribution parameters. The experimental results are discussed and compared with the results of the simulation. Finally, two parameter studies are carried out which indicate the sensitivity of the simulation results on the input data, i.e. the thermodynamic and diffusion databases.