Abstract
With solution treatment at 800°C, ferritic Fe-5Ni-2Al alloy showed almost the same age hardening property as that of solution treated one in full austenite condition. By utilizing this phenomenon, the precipitation process of ferritic Fe-Ni-Al alloy was investigated.
Two kinds of extra spots besides bcc lattice reflection were observed in the electron diffraction patterns of the aged specimens. The one was the spot due to epitaxial oxide film sometimes produced on the specimen surface, which could be removed by carefull treatment of the specimen. The other kind of spot was the super lattice reflections of ordered precipitates, and using this reflected beam, it wasreaffirmed through dark field image that CsCl type (B2) precipitates arise in the same orientation as the bcc matrix. In the aged Fe-5Ni-1Al-1.7Ti alloy DO3 type diffraction pattern was obtained, but not the case in Fe-5Ni-2Al alloy aged at 550°C or above. By measurements of electric resistivity andlattice parameter of a -solid solution parallel with observation of electron diffraction pattern, it was assumed that the precipitation of NiAl occurred from the beginning of aging, e. g., at 550°C.
