Synthesis and forming behavior of aluminium-based hybrid powder metallurgic composites

Aluminium-based metal matrix composites were synthesized from Al-TiO₂-Gr powder mixtures using the powder metallurgy technique and their forming characteristics were studied during cold upsetting. Green cylindrical compacts of pure Al, Al-5wt%TiO₂, Al-5wt%TiO₂-2wt%Gr, and Al-5wt%TiO₂-4wt%Gr were made using a 400-kN hydraulic press equipped with suitable punch and die and by sintering at (590 ± 10)℃ for 3 h. Cold upset forging tests were carried out, the true axial stress (σ_z), the true hoop stress (σ_θ), and the true hydrostatic stress (σ_m) were evaluated and, their behavior against the true axial strain (ɛ_z) was also analyzed. It is observed that the addition of 5wt% TiO₂ into the Al matrix increases σ_z, σ_θ, and σ_m. The addition of both TiO₂ and Gr reinforcements reduces the densification and deformation characteristics of the sintered preforms during cold upsetting. Microstructure analyses of the as-sintered and cold upset forged specimens also were carried out to substantiate the experimental results.