Effect of Mechanical Activation on Microstructure and Mechanical Properties of Aqueous Colloidal Processed Nickel Metal Matrix Nanocomposites

Previous works studied the colloidal processing of nickel-silica and nickel-titania nanocomposites fabricated via slip casting. A rheological approach was used to characterize and optimize a 30 vol.% nickel aqueous suspension with up to 10 vol.% SiO2 and 5 vol.% TiO2 nanoparticles. In this work, the effect of mechanical activation of Ni-SiO2 and Ni-TiO2 nanocomposites on microstructural and mechanical properties was studied. For this aim Ni-SiO2 and Ni TiO2 slip-cast compacts were attrition milled for up to 12 hours. Green bodies of the mechanical-alloyed powders were obtained by cold pressing (300 MPa). Next, those green bodies were annealed at 700 degrees C for 1 h, repressed at 700 MPa and sintered at 900 degrees C for 1 h in flowing Ar/5%H-2 atmosphere. Porous and dense materials were characterized by SEM/FESEM, Archimedes' densities and Vickers microhardness measurements. Mechanical alloying produces a remarkable improvement on microstructure homogenization, sintering densification and hardness comparing with slip-cast composites.