1993 Volume 79 Issue 12 Pages 1369-1373
The morphology of γ''precipitates extracted from a nickel-base superalloy, a modified NCF 3 type alloy (X-750M), was investigated mainly by transmission electron microscopy (TEM). The TEM images using carbon extracted replica of γ'' precipitates were clearer than those using electropolished thin film. The γ'' precipitates were disc shaped in the early stage of aging and became elliptic or irregular shaped plates in latter at up to 1033K, while they grew in rectangular shaped plates in latter at 1073K. Many of larger γ'' precipitates in the specimens aged at up to 1033K exhibited a considerable amount of internal fringe contrast. Selected area diffraction pattern from them showed continuons streaks normal to {112}γ''. The internal contrast is thought to be due to stacking faults. The internal fringe contrast was not observed in γ'' precipitates in the specimen aged at 1073K.
