HREM observation of the interface between Laves-phases and matrix phases in Inconel 718 by using a high-voltage electron microscope

The Ni-base alloy, Inconel 718 was observed with high-resolution electron microscopy using by a high-voltage electron microscope in order to analyze the morphology of the interface between Laves-phases and the austenite matrix phases. The Laves-phase had a plate shape and had a (004)_Laves∥{111}_γ; [11̄0]_Laves∥〈110〉_γ relationship in the interface with the matrix (γ). The interface had the step-structure although the interface looked like a planar shape macroscopically. It was considered that the step-structures were introduced to relax the lattice strain between the Laves-phases and the matrix. The step-structures were observed at intervals of almost 11.4-40.4 nm and 2.3-9.6 nm in the samples aged at 1 073 and 1 123 K, respectively. It was considered that the decrease of the interval of step-structure was due to the increase of the lattice strain between the Laves-phases and the matrix with increasing the aging temperature from 1 073 to 1 123 K.