CARBIDE FORMATION UPON TEMPERING AT LOW TEMPERATURES IN Fe-Mn-C ALLOYS.

Abstract

Carbide formation in Fe-4. 1 mass%Mn-1. 25 mass%C and Fe-5. 2 mass%Mn-0. 93 mass%C alloys have been examined by means of X-ray and electron diffraction and electron microscopy. Upon tempering at 358 K, the martensite lattice parameters change in two stages as a function of tempering time. In the preliminary stage, a long period ordered tetragonal phase, being a modification of Fe//4C carbide, is formed. Another diffraction effect suggesting the formation of a modulated structure and/or a short range order of carbon atoms has also been observed. The intermediate carbide in the first stage is identical to eta -carbide found by Hirotsu et al. in Fe-C alloys.