Spinodal decomposition which occurs at a temperature higher than 475 d
egrees C in Fe-Cr-Co alloys (chromindur), plays a prominent part in th
e embrittlement phenomenon and strongly influences the magnetic proper
ties. In the present study, the spinodal decomposition in the Fe-31Cr-
12Co alloy has been investigated using Fe-57 Mossbauer effect as a fun
ction of aging time at a temperature of 520 degrees C. An addition of
Cobalt causes a transition of the aging behaviour from the nucleation
and growth to the spinodal decomposition and rises its decomposition t
emperature. Mossbauer spectra for the as-quenched alloy, takes at 300
K, show a typical magnetic sextet with broad lines: the hyperfine stru
cture can be reproduced by using a distribution of hyperfine fields co
nsistent with the presence of various kinds of iron environments. The
aging at 520 degrees C, reveals the presence of three main environment
s: a Co-rich Fe phase with high concentration of Co, a Fe phase and a
(Fe, Cr) phase with high concentration of Cr.