FORMATION MECHANISM OF NiAl/TiC NANOCOMPOSITE BY MECHANICAL ALLOYING

Ni, Al, Ti, and C powders mixed at a composition of Ni37Al37Ti37C13 were milled in a high-energy ball mill.Upon milling for 107 min,an abrupt reaction occurred, resulting in in situ formation of NiAl and TiC compounds.The formation mechanism is suggested to be two separated combustion reactions, i.e. Ni+Al→NiAl and Ti+C→TiC. The combustion reaction conducted incompletely and small amount of elemental powders still existed. Prolonged milling led to gradual formation of NiAl and TiC as well as the refinement of grain sizes. The final saturated grain size for TiC is 2.5 times as large as that for NiAl, though TiC has a much higher melting point compared with NiAl, this is attributed to a different deformation mechanism.