Synthesis and thermal analysis of nanocomposites based on intermetallic compounds in the Ni-Al system and Al₂O₃

This study investigated the synthesis of intermetallic compounds in the Ni-Al system based nanocomposite powders with Al₂O₃ 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 Ni₃Al₄ phases and after 2 h for Ni₃Al phase. The unreacted NiO present in as milled powder is reduced by Al at 590°C on heating. The TEM micrographs of 3 h milled NiAl-Al₂O₃, Ni₃Al₄-Al₂O₃ and Ni₃Al-Al₂O₃ powder particles reveal the nanocrystallinity of the powders.