Ultra-high temperature deformation in a single crystal superalloy: Mesoscale process simulation and micromechanisms

A mesoscale study of a single crystal nickel-base superalloy subjected to an industrially relevant process simulation has revealed the complex interplay between microstructural development and micromechanical behaviour. As sample gauge volumes were smaller than length scale highly cored structure parent material from which they produced, their subtle composition differences gave rise differing work hardening rates, influenced by varying secondary dendrite arm spacings, γ′ phase solvus temperatures topologically inverted γ/γ′ microstructure. The precipitates possessed characteristic butterfly morphology, resulting simultaneously active solute transport mechanisms thermally favoured octodendritic growth N-type rafting, indicating creep-type prevalent. High resolution-electron backscatter diffraction (HR-EBSD) characterisation reveals deformation patterning that follows microstructure, with high geometrically necessary dislocation density fields localised interfaces; Orowan looping is evidently mechanism mediated plasticity. Examination residual elastic stresses indicated precipitate morphology had significantly enhanced heterogeneity, in stress states within γ channels favour slip, encourage further protrusions. combination such plasticity are considered be critical formation recrystallisation defect subsequent post-casting homogenisation heat treatments.