Abstract
This work investigates the influence of spark plasma sintering (SPS) parameters on the microstructure and mechanical properties of consolidated aluminum powders processed by high-energy ball milling under an air atmosphere. Sintering was performed under vacuum at various temperatures ranging from 550 °C to 625 °C and under pressures between 50 and 100 MPa. The particle size, crystallite size, and microstructure of the powders and the consolidated pellets were analyzed using laser granulometry, X-ray diffraction (XRD), scanning electron microscopy (SEM), and Archimedes' density measurements. Mechanical properties were evaluated via Vickers microhardness, nanoindentation, and tribological testing. For comparison, unmilled aluminum powders were also consolidated and characterized. After 46 h of milling, the aluminum crystallite size was reduced from 74 nm to 68 nm. The sample's density increased with higher sintering temperature and pressure. The aluminum sintered at 600 °C and 100 MPa after 46 h of milling exhibited the highest microhardness (187.5 HV). Nanoindentation tests were conducted to characterize different microstructural regions formed after SPS, revealing two distinct zones: one hard and one soft. The tribology results revealed that the SPS-consolidated samples of milled powders exhibited a reduction of 50% in specific wear rate and a reduction of 20% in the coefficient of friction compared to the SPS-sintered samples of unmilled powders.