AN ATOM-PROBE FIELD-ION MICROSCOPE STUDY OF MODEL NI-AL SUPERALLOYS CONTAINING BE

Atom probe field ion microscopy and transmission electron microscopy h ave been used to characterise the phases present, and their compositio ns, in four model NI-AI superalloys containing Be. In agreement with t he limited information available on phase stability within the ternary Ni-Al-Be system, atom probe results indicated that these alloys were in the three phase, gamma-Ni, gamma-Ni3Al and beta-NiBe, region of the ternary diagram. Beryllium was found to substitute on the 'Al' sites within the gamma', consistent with previous results from Be-doped NiAl . The experimental results have shown that the Be additions have resul ted in the precipitation of phases enriched in Be within the gamma' ph ase. The morphology of the phases enriched in Be ranged from monatomic ally thick plates to lenticular precipitates. Hardness measurements in dicate significant hardening resulting from the addition of Be to mode l Ni-Al alloys.