On the Formation of Multiply Coherent \(\upgamma \) Grains in a Powder Metallurgy Ni Base Superalloy

In this study, a unique microstructureMicrostructure where \(\upgamma \) grains contain multiple coherent primary \(\upgamma '\) particles is reported. We term these unique features “multiply coherent grainsMultiply coherent grains” (MCGs). While the \(\upgamma \) grains containing coherent primary \(\upgamma '\) particles suggest theHeteroepitaxial recrystallization heteroepitaxial recrystallization (HeRX) mechanism, HeRX can only explain the presence of a single coherent primary \(\upgamma '\) within a given \(\upgamma \) grain, not multiple. Other potential formation mechanisms of MCGs are assessed using combined energy dispersive spectroscopy and electron backscatter diffraction, then a likely formation mechanism is posited. The median grain sizeGrain size of MCGs surpasses other \(\upgamma \) grains, which shows the potential impact of MCG formation on the grain size distribution.