Reaction Processing of Al₂O₃ Composites Containing Iron and Iron Aluminides

Abstract

composites with metallic contents up to 30 vol% have been fabricated via reaction processing of Al 2 O 3 , Fe, and Al mixtures. Low Al contents (<∼10 vol%) within the starting mixture lead to composites consisting of Fe embedded in an Al 2 O 3 matrix, whereas aluminide-containing Al 2 O 3 composites result from powder mixtures with higher Al contents. In both cases, densification up to 98% TD can be achieved by pressureless sintering in inert atmosphere at moderate temperatures (1450°-1500°C). The proposed reaction sintering mechanism includes the reduction of native oxide layers on the surface of the Fe particles by Al and, in the case of mixtures with high Al contents, aluminide formation followed by sintering of the composites. Density and bending strengths of the reaction-sintered composites depend strongly on the Al content of the starting mixture. In the case of samples containing elemental Fe, crack path observations indicate the potential for an increase of fracture toughness, even at room temperature, by crack bridging of the ductile Fe inclusions.

Microstructure of Alumina Composites Containing Niobium and Niobium Aluminides

“…4 The results show that the addition of Al can improve the densification process by reducing the native oxide scale of the Fe powder. 4 Depending on the initial powder composition, composites consisting of Fe and Al 2 O 3 (Al content Ͻ 10 vol%) or FeAl and Al 2 O 3 (Al content Ͼ 10 vol%) were obtained. This was related to the larger heat of formation of the native oxide reduction compared to the aluminide formation.…”

“…Further details of the processing technique are reported elsewhere. 4,14 The densities of composite C1 and C0 were ϳ98% and ϳ95% of the theoretical density, respectively (Table I) …”

Preparation of Fe-Al intermetallic / TiC-Al2O3 ceramic composites from ilmenite by SHS

“…Intermetallic ceramic matrix composites (I/CMC) not only maintain the good properties of each phase, but also bring some new virtues due to the interaction of each phase. It has some good properties including the toughness of the intermetallics and the strength, hardness of the ceramics [1,2] .…”

Sliding wear of Cr–Al2O3–ZrO2 and Mo–Al2O3–ZrO2 composites

“…TiO 2 or Fe 2 O 3 , is converted to a composite consisting of aluminides and alumina by a redox reaction between aluminum and the metal oxide. [2][3][4][5][6][7] Because these redox reactions are usually highly exothermic, careful process control is required in order to avoid thermal runaway with possible detrimental effects on the product. In contrast to this, s-MAC precursors consist of Al 2 O 3 , a metal powder such as Cr, Mo, or Fe, and only a small fraction, typically <1 wt.%, of Al.…”