Mechanical properties, microstructural and thermal evolution of Mg₆₅Ni₂₀Y_15−xSix (X = 1, 2, 3) alloys by mechanical alloying

We report on a work of the influence of the mechanical alloying on the microstructure, thermal and mechanical features of Mg₆₅Ni₂₀Y_15−xSi_x (X = 1, 2, 3) alloys. The Mg-based alloys were produced by mechanical alloying technique from mixtures of pure crystalline Mg, Ni, Y and Si powders. These alloys were investigated using a variety of analytical techniques including x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDX) and differential scanning calorimetry (DSC). The mechanical properties of the alloys were investigated by Vickers microhardness (HV) tester. After 75 h of milling time, three different intermetallic phases were obtained. These phases were defined as Mg₂₄Y₅, Mg₂Ni₃Si and Mg₂Ni by XRD data. The particle and crystallite sizes of the Mg-based alloys were decreased by increasing milling time and they were calculated 2 μm and ∼9 nm, respectively. From the EDX analysis, it was determined that compositional homogeneity of the Mg-based alloys was fairly high. The microhardness values of the Mg₆₅Ni₂₀Y_15−xSi_x (X = 1, 2, 3) alloys increased by increasing Si into the alloys and were determined 101, 131 and 158 HV, respectively. (paper)