STRUCTURE OF HIGH-NITROGEN FE-18-PERCENT-CR ALLOYS

The Fe-18% Cr alloys containing 0.6, 0.9, 1.1, and 1.3% N are studied by electron microscopy and X-ray diffractometry after quenching from v arious temperatures. The type of structure formed in the alloy due to quenching (austenite; austenite + martensite; martensite + chromium ni trides; or ferrite + chromium nitrides) and the character of the decom position during aging are determined by the temperature of hearing for quenching and by nitrogen content in the alloy. The austenite decompo sition begins with the formation of the mixed zones of Cr and N atoms with concurrent (gamma --> alpha) transformation. Further, the mixed z ones transform to The CrN nitrides having the Bl NaCl-type lattice wit h tetragonal distortions, Further coarsening of the nitrides present i n as-quenched structure occurs during aging.