Evolution of Nanocrystalline Structures Using High Energy Ball Milling of Quaternary $Mg_{1.75}Nb_{0.125}C_{0.125}Ni$ and Binary $Mg_2Ni$

High energy ball milling of two initial quaternary and binary powder mixtures of $Mg_{1.75}Nb_{0.125}C_{0.125}Ni$ and $Mg_2Ni$ has been carried out in pure argon atmosphere for the synthesis of nanocrystalline powders based on $Mg_2Ni$ intermetallic compound. A planetary ball mill was employed using a ball to powder weight ratio of 20:1 for various milling time of 5, 10, 15, 20, 30 and 60 h. Characterization of the crystal structure of the milled products using X-ray diffractometry exhibited the formation of $Mg_2Ni$-based nanocrystallites after ≈ 5 h of milling for the both powder mixture. However, its volume fraction was greater in the case of quaternary powder mixture than that of binary one. In addition, an amorphous phase was detected in the milled products; its volume fraction showed increase by increasing milling time. The calculated mean crystallite size of $Mg_2Ni$ structure showed decrease by increasing the milling time following the Williamson-Hall procedure and was found to be ≈ 8 and 10 nm after 20 h of milling for the initial powder mixture of $Mg_{1.75}Nb_{0.125}C_{0.125}Ni$ and $Mg_2Ni$, respectively.