Antiphase boundaries in a rapidly solidified alloy were examined, by means of transmission electron microscopy, in the as-solidified state or after annealing. Dark-field imaging suggested that the antiphase boundary thickness increased with temperature during annealing, and that a dark disordered phase appeared at temperatures above about 800C. The boundary region at high temperatures had a chemical composition which was close to that (15at%Al) which was expected, on the basis of the equilibrium diagram, for the disordered phase. The examination of antiphase boundaries by using high-resolution electron microscopy did not confirm the disorder. The so-called disordered regions which exhibited dark contrast may have been caused by a significantly modified chemistry of the ordered regions. It was unclear whether disorder could form at high temperatures, when the average alloy composition entered the 2-phase, ordered+disordered region, or whether extensive segregation to the antiphase boundary simply took place without the appearance of a true second disordered phase.

The Structure, Thickness and Chemistry of Antiphase Domain Boundaries in Heat-Treated Rapidly Solidified Ni3Al. J.F.Perez, P.Shang, D.G.Morris, I.P.Jones: Philosophical Magazine A, 1999, 79[1], 179-92