Effects of Fe/Si Stoichiometry on Formation of Fe3Si/FeSi-Al2O3 Composites by Aluminothermic Combustion Synthesis

Aluminothermic combustion synthesis was conducted with Fe2O3–Al–Fe–Si reaction systems under Fe/Si stoichiometry from Fe-20 to Fe-50 at. % Si to investigate the formation Fe3Si/FeSi–Al2O3 composites. The solid-state combustion was sufficiently exothermic to sustain the overall reaction in the mode of self-propagating high-temperature synthesis (SHS). Dependence of iron silicide phases formed from SHS on Fe/Si stoichiometry was examined. Experimental evidence indicated that combustion exothermicity and flame-front velocity were affected by the Si percentage. According to the X-ray diffraction (XRD) analysis, Fe3Si–Al2O3 composites were synthesized from the reaction systems with Fe-20 and Fe-25 at.% Si. The increase of Si content led to the formation of both Fe3Si and FeSi in the final products of Fe-33.3 and Fe-40 at.% Si reaction systems, and the content of FeSi increased with Si percentage. Further increase of Si to Fe-50 at.% Si produced the FeSi–Al2O3 composite. Scanning electron microscopy (SEM) images revealed that the fracture surface morphology of the products featured micron-sized and nearly spherical Fe3Si and FeSi particles distributing over the dense and connecting substrate formed by Al2O3.