Milling criteria for the synthesis of nanocrystalline NiAl by mechanical alloying

The optimum milling parameters and energy domains for the synthesis of nanocrystalline NiAl by mechanical alloying was determined. The long-range ordered structure of NiAl under various milling conditions was also evaluated. Dominant role of the total energy of the grinding balls over the impact energy of each ball in the phase formation process was observed. A total energy of 200 kJ kg−1 was found necessary to trigger the NiAl formation from an equiatomic Ni–Al blend during mechanical alloying in stainless steel as well as in tungsten carbide media. The completion of the reaction required 550 and 700 kJ kg−1 of total energy in the stainless steel and tungsten carbide media, respectively. The low-energy requirement for the NiAl synthesis in stainless steel media was attributed to the Fe-contamination during ball milling. A close relation between the enthalpy of formation of the compound and the total energy of the grinding balls for its formation was observed.