Microstructure based constitutive model for the mechanical behavior at high temperatures of nickel-base single crystal superalloys

摘要

A constitutive law is proposed for single crystal superalloys with a large volume fraction of the gamma ' phase in the high temperature regime. It relies on a mechanical model of the dislocation mechanisms in the matrix and the particles. The microstructure is taken as periodic. The homogenization problem is solved by Fourier series within the approximation of uniform plastic deformations in the three kinds of channels and in the precipitates. In particular, the internal stresses due to non-uniform deformations in the periodic cell and to the different lattice parameters in the matrix and the particles are estimated. Shearing of the precipitates by superlattice Intrinsic Stacking Faults (SISF) and climbing of loops around the precipitates are taken into account. These mechanisms are responsible for the relaxation of the internal stresses (recovery) and the secondary creep. Alloy: SRR99.