A tensorial thermodynamic framework to account for the γ ′ rafting in Nickel-based single crystal superalloys

Rodrigue Desmorat (1) , Adriana Mattiello (2, 1) , Jonathan Cormier (3)

1 LMT - Laboratoire de Mécanique et Technologie
2 Safran Helicopter Engines
3 PPrime [Poitiers] - Institut Pprime [UPR 3346]

A new model is developed in order to account for the effect of microstructural degradation (i.e. precipitate-directional-coarsening) on the viscoplastic behavior of single crystal superalloys under high temperature exposure. Microstructural changes are modeled by a tensorial description of γ channel width evolution formulated in the natural anisotropy basis of the material. The tensorial description of microstructural evolution is combined with the Kelvin modes based viscoplasticity laws thanks to the coupling with the Orowan stress performed within a thermodynamics framework. Isotropic and directional coarsening of the γ ′ hardening phase are modeled as well as its dissolution with temperature changes. Results are presented for isothermal creep of CMSX-4 alloy at 1050 • C along < 001 > and < 111 > crystal directions but the formulation allows to account for anisothermal loadings, isotropization of the creep response at high temperature and misaligned loadings. This newly developed tensorial framework for rafting can also apply to single crystal superalloys having a positive misfit.

Mots clés: Ni-based single crystal superalloys; Microstructure evolution; Creep; Anisotropy

Domaines: Mécanique des matériaux [physics.class-ph]

Rodrigue Desmorat, Adriana Mattiello, Jonathan Cormier. A tensorial thermodynamic framework to account for the γ ′ rafting in Nickel-based single crystal superalloys. 2016. ⟨hal-01438310⟩