Densification and deformation studies on powder metallurgy Al–TiO₂–Gr composite during cold upsetting

Aluminum metal matrix hybrid composites were synthesized through powder metallurgy route from ball milled powders to yield the compositions: Al + 0% TiO2, Al + 2.5% TiO2, Al + 2.5% TiO2+ 2% Gr, and Al + 2.5% TiO2+ 4% Gr. The densification and deformation properties of sintered Al–TiO2–Gr composites during cold upsetting were investigated experimentally. The powder preforms are compacted using suitable punch and die in 40 kN hydraulic press and the initial percentage theoretical density was maintained as 85%. Sintering was done in an electric muffle furnace at the temperature of 590 °C for a period of 3 h. The sintered preforms were subjected to incremental compressive loading of 10 kN until cracks were found at the free surface. The true axial stress (σz), true hoop stress (σθ), true hydrostatic stress (σm), and true effective stress (σeff) were calculated for all the preforms and all these stresses are correlated with the true axial strain (εz). The densification behaviors of the composites were studied against true axial strain (εz) and lateral strain. Better densification and deformation property were obtained for pure aluminum preforms compared with other composite preforms. Addition of TiO2to the pure Al and Gr reinforcements increases the strength coefficient of the Al–TiO2composite.