- The effects of MgO as a sintering additive, sintering duration, and post-heat treatment on mechanical properties and microstructure of spark plasma-sintered aluminum powders were investigated. The sinterability of aluminum with or without MgO was found to be sensitive to the aluminum average particle size, meaning the amount of native oxide within the raw aluminum powders. The fracture mode changes gradually from a brittle mode (after short SPS), through a mixed brittle-ductile fracture mode (after long SPS), ending with the pure ductile form (short SPS followed by heat treatment). Maxima flexural strength and elongation were found in samples with particles size of about 44 μm and the addition of 2 wt.% MgO after short SPS process followed by an additional heat treatment. The addition of MgO may contribute to perforation of the aluminum native oxide and enhance aluminum diffusion during the heat treatment.