SYNTHESIS OF NANOCRYSTALLINE NIAL OVER A WIDE COMPOSITION RANGE BY MECHANICAL ALLOYING

The paper reports the synthesis of nanocrystalline NiAl by mechanical alloying of pure metal mixture and a mixture of prealloyed powder with Ni/Al. A large number of compositions have been studied to establish the phase field of NiAl in the milled state. The phase field of NiAl i n the ball milled condition was found to be much wider (10-68 at.% Ni) than its equilibrium phase field (45-59 at.% Ni). The metastable equi librium achieved by mechanical alloying was identical for a given comp osition irrespective of the starting ingredients. The crystallite size of NiAl reached a minimum (5 nn) at the phase boundary of NiAl/Ni3Al.