Microstructural characteristics of iron based alloy laser clad on Al–Si alloy

Abstract

The present study investigates some special microstructural characteristics and the diffusion phenomenon occurring in the laser cladding of an iron based alloy (a less commonly used alloy) on an Al–Si eutectic alloy. Among the three microstructural regions, i.e. the clad region, the transitional region, and the post-molten region, the transitional region is non-uniform in both microstructure and composition, in which the aluminium rich area displays a mixture of invisible and snowflakelike morphologies while the iron rich area has an ultrafine lamellalike structure and the transitional zone between them appears as a network structure. Differential scanning calorimetry and X-ray diffraction analysis carried out in the transitional region revealed that the possible phases existing in the three areas are γ-Fe, NiAl, and Fe₂ Al₅ in the iron rich area, α-Al and NiAl₃ in the aluminium rich area and FeAl₃, Fe₂ Al₅, and NiAl₃ in the transitional zone, respectively. Furthermore, the solidification process of the pool and the bond mechanism have been discussed in relation to the microstructural characteristics observed in the experiments, the properties of materials and the extent of thermal conduction.