Alloying Reaction of Aluminized Steel Sheet

Abstract

Aluminized steel has excellent heat resistance because of the stable oxide film that forms on its surface. Thus, it is often used for parts that are required to be exposed to elevated temperature. When aluminized steel is heated to temperatures above 873 K, diffusion occurs between the plating layer and the steel substrate; as a result, the plating layer is composed of a mixture of several intermetallic compound layers. In this study, aluminized steel was heated at 873 K for various heating times. The composition of each layer formed on the surface of the specimens was analyzed by SEM-EDS, and each layer was identified by comparing the analyzed composition with an Al–Fe–Si phase diagram obtained by using Thermo-calc. The diffusion path between the aluminized layer and steel substrate was determined at 873 K. The layer formed in the middle of intermetallic layers was observed to have lower Al content than other layers. Judging from the composition of the layer, it can be inferred that it consists of a mixture of fine grains in two phases. TEM-EDS analysis indicated that this layer consisted of a mixture of Fe₂Al₅ and τ₁ phase.