Reactive milling processes were performed for NiO + Al powder mixture in order to obtain "in situ" composite with NiAl matrix reinforced with alumina. A combustion type of reaction was observed and the formed particles exhibited a polyhedron morphology and size about 150 mum. Prolonged milling led to particle size refinement down to 10 mum and change of morphology into spherulitic. The Hall-Williamson analysis revealed an anisotropy in crystallite size and lattice strain. Adding powders of products (NiAl ore Al2O3) allowed to avoid a combustion type of reaction.