SYNTHESIS OF MMNI4.5AL0.5 BY MECHANICAL ALLOYING

We report the synthesis of aluminium-substituted mischmetal pentanicke lides (MmNi4.5Al0.5) using ball milling. A stoichiometric mixture ot m ischmetal, nickel and aluminium, when subjected to ball milling for 10 0 h in an argon atmosphere, led to the formation of MmNi4.5Al0.5. The synthesized powder was characterized by X-ray diffraction and transmis sion electron microscopy. The low-temperature annealing of the ball-mi lled powder (600-degrees-C, 30 min) has been found to improve its crys tallinity. Ball milling followed by low-temperature annealing yielded a MmNi4.5Al0.5 phase nearly identical to that prepared through high-te mperature melting of the ingredients. Both XRD and TEM characterizatio ns have confirmed the formation of alloy MmNi4.5Al0.5. Extensive elect ron microscope investigation revealed the presence of the modulated ph ase in local regions with modified periodicities (a = 4a0 and c = 2c0) .