DECOMPOSITION OF AN FE-CR 38-WT-PERCENT CHROMIUM STAINLESS-STEEL AT 475-DEGREES-C

The physical changes occurring at 475 degrees C in an Nb and Al stabilized stainless steel containing 38 wt.% Cr have been studied by Mossbauer spectroscopy. The specimen started to decompose when held at 475 degrees C. Decomposition still continues after 500 hours into a paramagnetic Cr-rich alpha'-phase and a nearly pure Fe alpha-phase. The magnetic field distribution of the initial sample indicates that considerable decomposition has already taken place into an alpha'-phase with an estimated 15 at.% iron, and an iron-rich alpha-phase with an estimated 18 at.% Cr.