Effect of milling time and compaction pressure of Alumina – Titania composite prepared by powder metallurgy route

Aluminium oxides or alumina (Al2O3) had been used widely in various high performance application since it possesses many excellent properties such as high corrosion resistance and good wear resistance but Al2O3 also has a few weaknesses which need to be overcome such as low flexural strength. Many researchers suggest reinforcing Al2O3 with other materials such as TiO2 in order to enhance it properties. Therefore, this study was carried out to synthesis the Al2O3 – TiO2 composite powder by powder metallurgy route and to investigate it properties with different milling times and compaction pressure. The composite powder was produced via low energy ball milling with constant milling speed at 200 rpm and milled with different milling times (30, 60, 90 and 120 h). The as-milled powder was cold compacted with 200, 400, 600 and 800 MPa. X-ray diffraction (XRD), scanning electron microscope (SEM), Archimedes’ principle was used to determine the phase identification, morphology and green density, respectively. The Al2O3 crystallite size and internal strain was calculated using Williamson-Hall method and composite powder compressibility was analysed using Panelli – Ambrozio equation. There is no new phase formed even after 120 h of milled was detected. The lowest crystallite size and the highest internal strain of the composite were recorded in 120 h of milled sample. Increasing milling time produced homogeneous dispersion and finer composite particles. In this study, the highest green density was obtained at 800 MPa in 120 h of milled. The densification of Al2O3 - TiO2 composite was improved as the compaction pressure increase and the reduction in porosity was detected. The higher compressibility was obtained at 120 h of milled attributed to finer particles compared to early milling time as a result of higher generation of lattice defects.