Morphological changes of γ′ precipitates in superalloy IN738LC at various cooling rates

The effect of cooling rate from a temperature below the gamma' solvus on morphology of gamma' in a Ni-base superalloy, IN738LC, was investigated. At high cooling rates, gamma' showed solid-state morphological instability and as the cooling rate decreased, gamma' reduced in size and the growth occurred in a stable manner. The morphology changed from a cubic shape to a complex and flower-like shape as the cooling rate increased. The shape changes observed in this study Suggested that the cooling rate has a significant impact on the misfit between gamma and gamma'. The morphological instability of gamma' is believed to be controlled by the degree of supersaturation in the Matrix. (C) 2008 Elsevier B.V. All rights reserved.