Determination of γ–γ′ lattice misfit in a single-crystal nickel-based superalloy using convergent beam electron diffraction aided by finite element calculations

In single-crystal nickel-based superalloys, the lattice mismatch associated with interface coherency between γ matrix and γ′ precipitates has a strong influence on mechanical properties. The unconstrained lattice misfit in a single-crystal of the MC2 nickel-based superalloy is determined using convergent beam electron diffraction measurements and finite element calculations. The apparent lattice parameters of both constrained phases are obtained in thin foils, using a new multi-pattern approach, which allows for unambiguous determination of all the lattice parameters considering the real symmetry of the strained crystals. Finite element calculations are used to establish relations between the constrained and unconstrained lattice parameters, with the stress relaxation resulting from the thin foil geometry taken into account.

► We study the unconstrained lattice misfit in single-crystal nickel-based superalloy.
► Two techniques have been used: CBED and finite element calculation.
► The lattice parameters of phases are obtained by a new CBED multi-pattern approach.
► The stress relaxation resulting from the thin foil geometry was taken into account.
► We present a new method (CBED + FE) for the determination of the unconstrained misfit.