Coherency elastic strain between γ and  is one of the effective factors which affect the morphology, spatial re-arrangement and coarsening kinetics of  precipitates in nickel-base superalloys. In this investigation, using X-ray diffraction (XRD) technique, the - constrained and unconstrained lattice misfits were calculated for different morphologies of the  precipitates in Inconel 738LC nickel-base superalloy. The constrained and unconstrained misfits, hence the coherency elastic strains of different morphologies of the  precipitates were calculated from the XRD patterns of the bulk sample and electrolytically extracted  precipitates, respectively. According to the results, as the sizes of the  particles increased the - coherency as well as the compressive strain of the  precipitates was reduced and consequently their morphology changed from spherical to cubic, then flower-like, and finally dendritic shapes.

Keywords: Nickel-base superalloy, Coherency, Constrained misfit, Unconstrained misfit, Elastic strain, Morphology, X-ray diffraction.

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