Formation of NiAl–Al2O3 intermetallic-matrix composite powders by mechanical alloying technique

This study investigated the feasibility of preparing intermetallic-matrix composite powders (NiAl/Al2O3) by mechanical alloying of Ni, Al and Al2O3 powder mixtures with various compositions of (NiAl)x(Al2O3)100–x. The as-milled powders were examined by X-ray diffraction, scanning electron microscopy, and differential thermal analysis. The formation of NiAl phase was noticed after 5 h of milling. Intermetallic-matrix composite powders (NiAl/Al2O3) were prepared successfully at the end of milling for (NiAl)x(Al2O3)100–x (x=79, 66, and 49), but no alumina phase was detected for (NiAl)95(Al2O3)5. It is suspected that the additions of alumina hampered the cold welding and fracturing process. The thermal analysis of (NiAl)x(Al2O3)100–x powders after 1 h of milling revealed that the transition temperature of NiAl phase increased with increasing amount of Al2O3 additions.