Fine Aluminium Nitride Precipitates in Steel

Abstract

FOR the past thirty years, aluminium has been commonly used in controlling the deoxidation, and thus the properties, of a number of steels. As a result of this practice there are important consequences if an appreciable amount of nitrogen is present. Aluminium in steel is known to be able to form one of the most stable nitrides. It is generally believed that under certain conditions aluminium nitride appears as inclusions after the solidification of the steel. Many investigators^1–5 have reported findings relative to aluminium nitride. Chemical and X-ray analyses of the residue have confirmed the presence of aluminium nitride in steel. Despite these claims, however, exact knowledge concerning the occurrence of aluminium nitride with respect to the structure of steel is not yet available. This communication reports the result of an attempt at identifying and separating fine aluminium nitride particles from a sample of nitrided vacuum-melted steel with the use of the electron microscope.