Production and characterization of Ni2AlSi nanocrystalline intermetallic compound via mechanical alloying process

In this research, Ni2AlSi intermetallic compound was synthesized by mechanical alloying and its formation mechanism was compared with NiAl intermetallic compound during mechanical alloying. For this purpose, Ni50Al50 and Ni50Al25Si25 powder mixtures were mechanically alloyed for 30 h. Phase, microstructural and morphological evolutions of the powder mixtures were studied by X-ray diffraction and scanning electron microscope. Also, thermal behavior of the powders was investigated by differential thermal analysis. It was found that NiAl and Ni2AlSi nanocrystalline intermetallic compounds were successfully synthesized after 30 h of mechanical alloying. The reaction pathway of Ni50Al50 powder mixture was direct reaction between Ni and Al elemental powders to produce NiAl intermetallic compound without any solid solution formation or intermediate phase during mechanical alloying. Also, during mechanical alloying of Ni50Al25Si25 powder mixture, first NiAl intermetallic compound formed. In continue, with dissolution of Si into NiAl lattice, (Ni,Si)Al intermetallic compound formed. Finally, with further mechanical alloying, (Ni,Si)Al phase transformed to ordered Ni2AlSi intermetallic compound (super lattice structure).