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.