Development of Binary Fe-Al Intermetallic Compounds by Non-Pressurizing Cladding and Heat Treatment

Binary Fe-Al intermetallic compounds were developed by combining a non-pressurizing cladding with a simple heat treatment. Thin plates of pure Fe and pure Al were alternately laminated, followed by heat treatment at temperatures higher than the melting point of Al ranging from 973 K to 1473 K in an Ar atmosphere. A tongue-like diffusive layer consisting of Fe2Al5 was initially formed and the melted Al was disappeared in the specimen heated for 900 s at temperatures ranging from 973 K to 1273 K. By increasing the heating time up to 10.8 ks, the layers of FeAl and alpha-Fe with Al were formed in the region between the tongue-like diffusive layer and the Fe substrate. In addition, the tongue-like diffusive layer changed the constituent phase from Fe2Al5 to FeAl2 because of the decrease in the Al content of the layer. By heating at more than 1373 K, the layers of FeAl and Fe with Al were only formed, resulting in the disappearance of Fe2Al5 and FeAl2. The specimen heated at 1473 K for 10.8 ks has the uniform chemical composition in whole area. However, it shows a lower Al content than the theoretical composition, since the melted Al oozed outside the specimen with increasing the heating temperature. In order to suppress the decrease in the Al content, the specimen was heated at 973 K for 3.6 ks, followed by heating at 1473 K for 10.8 ks. It was then possible to obtain the sample with the chemical composition which is approximate to the theoretical one.