Mechanical Alloying and Sintering of a Ni/10wt.%Al2O3 Nanocomposite and its Characterization

A Ni matrix nanocomposite reinforced by 10 wt.% Al2O3 was fabricated by mechanical alloying. The powders mixture was milled up to 24 h in a ball mill. Phase composition and morphology of prepared powders were investigated by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. To obtain compact bodies, pressing was applied on the milled powders; then sintered at different temperatures for 1 h in argon atmosphere. Furthermore, the effect of milling time and sintering temperature on microstructure. Physical, mechanical and electrical properties of the sintered nanocomposite specimens were evaluated. The results show decrease of particle size of milled powders (69 nm) as the time increased up to 24 h of milling with a noticeable presence of agglomerates. On the other hand, relative density, microhardness, compressive strength, elastic modulus and electrical conductivity of the sintered samples were found to progressively increase with the increasing of milling time and sintering temperature. Their maximum values were 97.36%, 1137 MPa, 633 MPa, 21.6 GPa and 9.71 x 10(5) S/m, respectively, for the sample that was milled for 24 h and sintered at 1200 degrees C. On the other hand, the increasing milling time tended to decrease the fracture strain while it increased with increase of the sintering temperature.