Formation of Voids Band along Interface between Subsurface Layer and Transition Layer of Aluminized Steel at High Temperature

The shape, distribution and formation of voids along the interface between the subsurface layer and transition layer of aluminized steel during oxidation at 800℃ were investigated. The variations of the average size and depth of the interfacial voids with oxidation time were examined by means of scanning electron microscopy (SEM). The results show that the wall of voids usually has particular crystallographic facets and the equilibrium shape of the voids has some dependence of the crystal orientation of the surrounding matrix. With oxidation time prolonging, the spherical voids become gradually polygonal void and its distribution changes from three-dimensional conical type into two-dimensional plane type. The growth of the voids can be divided into two stages: fast growth and stable growth. The depth of voids band first increases quickly and then unchanged. The formation mechanisms of the voids are discussed.