Abstract
Interdiffusion in Fe-Ni-Cr (fcc � phase) alloys with small additions of Si and Ge at 900�C
was studied using solid-to-solid diffusion couples. Alloy rods of Fe-24 at.%Ni, Fe-24 at.%Ni-
22at.%Cr, Fe-24 at.%Ni-22at.%Cr-4at.%Si and Fe-24 at.%Ni-22at.%Cr-1.7at.%Ge were cast using
arc-melt, and homogenized at 900�C for 168 hours. Sectioned alloy disks from the rods were
polished, and diffusion couples were assembled with in Invar steel jig, encapsulated in Argon after
several hydrogen flushes, and annealed atz 900�C for 168 hours. Polished cross-sections of the
diffusion couples were characterized to determine experimental concentration profiles using
electron probe microanalysis with pure elemental standards. Interdiffusion fluxes of individual
components were calculated directly from the experimental concentration profiles, and the moments
of interdiffusion flux profiles were examined to determine the average ternary and quaternary
interdiffusion coefficients. Effects of alloying additions on the interdiffusional behavior of Fe-Ni-
Cr-X alloys at 900�C are presented with due consideration for the formation of protective Cr2O3
scale.