1994 Volume 80 Issue 4 Pages 348-352
The morphology of γ″ precipitates extracted from a nickel-base superalloy, a modified Inconel 718 type alloy (718M), was investigated mainly by transmission electron microscopy (TEM). The TEM images using carbon extracted replica of γ″ precipitates were clearer than those using electropolis. hed thin film. The γ″ precipitates were disc-shaped in the early stage of aging and became rectangular-shaped plates in latter at up to 1033K, while they grew in 'propeller'-shaped plates with preferential growth along <110>γ″ directions in latter at 1073K. The morphology changes of the γ″ precipitates with the increase in aging time and temperature were dependent not only on the size of them but also on the chemical composition of the alloy.
The internal fringe contrast due to stacking faults on {112} plane of γ″ phase was not observed in the γ″ precipitates in the 718M unlike in a Ni-15Cr-8Fe-6Nb superalloy previously reported.
