Abstract
Effects of heat-treatments on microstructure of PAM René 95 consolidated by the hot-isostatic pressing (HIP) were examined in some detail. Microstructure of as-HIP'd specimen was characterized by highly serrated grain boundaries. It was clarified that such serrated grain boundaries were formed during slow cooling from HIP temperature across the γ′ solvus temperature. Grain boundaries were found to become smooth when the specimen was quenched from temperatures above the γ′ solvus temperature. Mechanical tests and microstructural observations revealed that the serrated grain boundaries improved ductility at both room- and elevated-temperatures by retarding crack propagation along grain boundaries. The creep properties of HIP'd and heat-treated specimens which contained serrated grain boundaries were found to be superior to the properties of cast +wrought material.
