Fabrication and characterization of alumina-based composites by in-situ combustion synthesis in Al-FeTiO3-B2O3-C alumino-thermic system

Abstract

In this study, thermal analysis, composition phase, microstructure and physical and mechanical properties of Al₂O₃-based composites with titanium diboride and carbide reinforcements fabricated by in-situ spark plasma sintering method in Al-FeTiO₃-B₂O₃-C alumino-thermic system have been investigated. This research explores the potential of utilizing Kahnuj (Iran-Kerman) ilmenite concentrate as a replacement for TiO₂. The results of the thermal analysis demonstrate that aluminothermic reactions significantly intensify after the melting of aluminum and different compounds of iron aluminides (FeAl, Fe₂Al₅, and Fe₃Al) and titanium diboride (TiB₂) and carbide (TiC) are formed. Among the different systems of raw materials (Al-FeTiO3-C, Al-FeTiO₃-B₂O₃, and Al + FeTiO₃ + C + B₂O₃) only for system Al + FeTiO₃ + B₂O₃, the intermetallic compounds of Fe₃Al and Fe₄Al₁₃ are stable. For heat treatment with higher heating rates, the boron oxide participates more effectively in the aluminothermic reaction and the composition of titanium diboride is more noticeably formed. In the condition of 45 MPa in mechanical pressure, argon gas atmosphere with 3 bar pressure, heating rate of 100 °C/min, temperature of 1400 °C with dwelling time of 4 min (Optimum condition) for in-situ SPS processing of Al-FeTiO₃-C system, the composite samples with the highest homogeneity in microstructure, density (4.10 g/cm³), hardness (281HV), bending strength (271.5 MPa) and highest wear resistance (Friction coefficient of 0.3 and 0.003 g of weight loss with 500 m of sliding distance) with optimal phase composition (Fe, Al₂O₃, TiC,…) was obtained.