The effect of oxides on Fe/Al interfacial reaction in Metal-Intermetallic Laminate (MIL) composites

Abstract

When fabricating Metal-Intermetallic Laminate (MIL) composites by hot pressing alternately stacked Al and Fe-based foils, the oxides on the surface of the sheets will affect the nucleation and growth kinetics of the intermetallic phases. The influence of the oxide surface layers on phase formation, growth kinetics and morphology of the intermetallic layer was studied by tracking the evolution of the initial oxide layer during interfacial reaction processing. The dominant intermetallic phase formed in the pure Fe/Al reaction was Fe2Al5 phase which preferentially grew along the dense packed direction of its unit cell ([001] direction in c-axis). In the early reaction stage, the morphology of aluminide growth is planar due to primarily two-dimensional diffusion. In the later stage of reaction, three-dimensional diffusion causes anisotropic growth of intermetallic layer with tongue-like morphology. The presence of the oxide layer also increases the growth rate of Kirkendall voids in the intermetallic phase.