Synthesis of nanocrystalline Mg-based alloy powders by mechanical alloying and their microstructural characterization

Nanocrystalline Mg₆₅Ni₂₅Y₅M₅ (M= Si, B, Ag) alloys have been produced by mechanical alloying from mixtures of pure crystalline Mg, Ni, Y and M powders using a Spex Industries Mill Model 8000 in order to characterize the influence of Si, B and Ag on the microstructure of Mg-Ni-Y alloy system. Microstructural evolution, thermal behavior and morphological changes of the mechanically alloyed powders at different stages of milling have been investigated using a variety of analytical techniques including x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDX), differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The present results revealed that the crystallite size of Mg₆₅Ni₂₅Y₅M₅ (M= Si, B, Ag) powders decreased with increasing milling time and it was determined in the range of 18–30 nm by TEM observation. After 65 h of milling, different intermetallic phases such as Mg₂₄Y₅, MgB₂, Mg₂Ni and Mg₂Ni₃Si were obtained. According to SEM images, particle size of the powders decreased during mechanical alloying and their shape and distribution became uniform. The compositional homogeneity of the Mg₆₅Ni₂₅Y₅M₅ (M= Si, B, Ag) alloys after mechanical alloying were confirmed by EDX analyses.