Mechanical thermal synthesis of in situ Al based hybrid nanocomposites in Al-Ni-Ti-O system

Al matrix hybrid nanocomposite is synthesized from a powder blend of Al-12% (wt) NiO-15% (wt) TiO2 by combined mechanical and thermal activation (mechanical thermal synthesis). The powder blends are mechanically activated by high energy ball milling followed by consolidation and thermal treatment. Milled powders are characterized by differential thermal analysis (DTA), X-ray diffraction (XRD) and electron microscopy. DTA results show the onset reaction temperature to decrease with increase in the milling time. Series of thermal treatments in a wide range of temperatures are performed on the green compacts. The thermally treated samples are then characterized by XRD and electron microscopy. The superior microhardness (1.86-2.25 GPa) of the nanocomposite may be attributed to ultra fine grain size of the Al matrix, and Orowan strengthening from the nanosized reinforcements. Aluminothermic reduction reaction between Al, NiO and TiO2 is successfully exploited for the synthesis of in situ hybrid nanocomposite by combined mechanical-thermal activation.