The structure of splat-cooled Fe-20% Cr-25% Ni austenitic steel

Abstract

A controlled atmosphere splat quenching gun has been used to produce splats of Fe-20% Cr-25% Ni. Three types of structure were observed by thin foil electron microscopy, namely high-angle cellular, low-angle cellular, and linear arrays of dislocation loops, which were determined primarily by the heat transfer conditions. In the thin, most rapidly cooled areas (lift-off regions) high-angle cellular structures were observed which were largely free of defects. As the cooling rate decreases there was a greater tendency for low-angle cellular structures to form, but at intermediate cooling rates bands of dislocation loops were observed. These are explained in terms of solute segregation and vacancy coalescence along 〈100〉_gg directions in the austenite.