TEM study of internal oxidation in an ODS-Eurofer alloy

Analytical TEM investigations of samples from an oxide dispersion-strengthened Eurofer batch show the formation of new type of precipitates of Fe–Cr–V–O composition and a size of 40–250 nm. Structural HRTEM analysis reveals that the precipitates consist of (Mn,Fe)(Cr,V)2O4 manganese chromium oxide of spinel structure. In some cases, the inclusions order along lines that can reach more than ten micrometers in length. Such lines of large particles might have a negative influence on the mechanical properties of the steel, as was observed. It is assumed that they form by internal oxidation during hot isostatic pressing due to the high oxygen content of the mechanically alloyed powder.