Combustion synthesis and development of Ti–O–C aluminium composites

Aluminium matrix composite reinforced with Ti compounds was successfully fabricated by SHS combustion synthesis and squeeze casting course. Prepared samples from mixture containing Ti, C and Al2O3 fibres were heated in microwave reactor to ignite synthesis and produce porous preform for subsequent infiltrating with liquid metal. Studies showed that synthesizing temperature has been remarkably increased by applying higher magnetron power and addition of graphite. Synthesis of specimens prepared from preliminary ball milled Ti and C powders proceeded at the highest propagation wave velocity. Microwave heating of metal Ti powder in the stream of CO2 resulted in formation of corrugated precipitates composed of titanium oxide with carbon inclusions TiO(C) and Ti2O3. The produced preforms were impregnated by squeeze casting with the aluminium alloy AlSi7Mg. Proper interface with slight reduction of Ti oxide between the reinforcement and the matrix was developed. Subsequently, the samples were annealed at 500 and 1000 °C. Annealing at the lower temperature induced creation of Ti3O2(C) and Al2O3. This process was continued at 1000 °C, and additionally some Ti(Al0,8Si0,2)3 pellets appeared in the matrix. With prolonged annealing, oxygen was completely removed from Ti compound and oval grains of Ti(C) were created, enveloped with Al2O3. In the matrix, larger and numerous Ti3AlSi5 pellets were formed. Hardness examination showed that the best strengthening effect was achieved after annealing at 1000 °C.

► A mixture of Ti and C powders with Al2O3 fibres was ignited for SHS synthesis.
► The prepared preforms were infiltrated with aluminium alloy.
► Annealing at 500 °C induced reduction of TiO(C) and creation of Ti3O2(C) and Al2O3.
► At 1000 °C oxygen was completely removed from Ti3O2(C) and oval grains of Ti(C) were created, enveloped with Al2O3.