MULTIPHASE DIFFUSION IN FE-NI-AL SYSTEM AT 1000-DEGREES-C .1. DIFFUSION STRUCTURES AND DIFFUSION PATHS

Multiphase diffusion was investigated in the Fe-Ni-Al system at 1000°C with several series of solid-solid diffusion couples assembled with selected β(bcc) and γ(fcc) alloys for the development of diffusion structures. The series of couples were characterized by a common β or γ terminal alloy joined to selected alloys of the other phase. The diffusion structures developed for the various couples exhibited interfaces of either planar, wavy, acicular, or flowery morphologies. Diffusion paths for the couples were determined by electron microprobe analysis. On the basis of isoconcentration contours in the vicinity of interfaces, the path-crossings of the (β+γ) two-phase region were found to be parallel to tie-lines for planar β/γ interfaces but were spread out into a band inclined to tie-lines for nonplanar interfaces. The band spread of path crossings for nonplanar β/γ interfaces showed compositional variations mainly on the γ-side of interfaces. © 1979 The Metallurgical of Society of AIME.