Synthesis and forming characteristics of Al–TiO 2 powder metallurgy composites during cold upsetting under plane stress state conditions

Abstract

Aluminum-based metal matrix composites with various weight percentages of TiO₂ reinforcement were synthesized by powder metallurgy technique and their forming characteristics were completely studied during cold upsetting under plane stress state conditions. The milled powders were characterized by scanning electron microscope, X-ray diffraction (XRD), and energy dispersive analysis using X-ray (EDAX) analysis. Green cylindrical compacts were made using a 400 kN hydraulic press using suitable punch and die, sintered at (590 ± 10)℃ for a period of 3 h, furnace cooled, and machined to obtain samples with 0.5 aspect ratio. The cold upset tests were carried out in steps of 10 kN and the true axial stress (σ _z ), the true hoop stress (σ_θ), the true hydrostatic stress (σ _m ), and the true effective stresses (σ_eff) were determined, and their behavior against the true axial strain (ɛ _z ) was thoroughly analyzed. It was observed that, the addition of TiO₂ to the Al matrix material increases the strength coefficient (K) and decreases the strain hardening index (n). The decrease in densification and deformation characteristics was observed for the addition of more weight percentages of TiO₂. The microstructure analysis was done for the cold upset samples and reported.