Synthesis and thermal analysis of nanocomposites based on intermetallic compounds in the Ni-Al system and Al sub(2)O sub(3)

This study investigated the synthesis of intermetallic compounds in the Ni-Al system based nanocomposite powders with Al sub(2)O sub(3) by mechanical alloying (MA) of NiO and Al powder mixture with various compositions. The structural changes of powder particles during mechanical alloying were studied by X-ray diffractometry (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The thermal analysis of as-milled powders was examined by differential scanning calorimetry (DSC). XRD results revealed that the intermetallic phase was first noticed for all compositions investigated in the current study after 1 h milling. The formation of intermetallic phase, however, was completed after 3 h milling for NiAl and Ni sub(3)Al sub(4) phases and after 2 h for Ni sub(3)Al phase. The unreacted NiO present in as milled powder is reduced by Al at 590 degree C on heating. The TEM micrographs of 3 h milled NiAl-Al sub(2)O sub(3), Ni sub(3)Al sub(4)-Al sub(2 )O sub(3) and Ni sub(3)Al-Al sub(2)O sub( 3) powder particles reveal the nanocrystallinity of the powders.