Evolution and characterization of a Ni₃Al intermetallic compound during mechanical alloying

Ni₃Al intermetallic powders were produced in the solid state using the mechanical alloying (ma) technique by milling Ni and Al powders in the Fritsch PM/5 planetary ball mill. The evolution and formation of the intermetallic compound were examined at different milling stages using a scanning electron microscope and X-ray diffraction, while the thermodynamic behaviour of the milled powders was studied by differential scanning calorimetry. Changes were observed in the overall composition as well as in each powder particle during the ma process. Homogeneity in composition was reached after 300 min of ma. However, after 1200 min of ma, both Ni and Al contents were found to decrease. A detailed energy-dispersive X-ray (edx) study showed that some contamination of Fe and Cr elements from the milling tools also occurred at this stage. An X-ray diffraction pattern confirmed the formation of a Ni₃Al intermetallic compound after 600 min of ma. The most suitable alloying time for Ni₃Al at a milling speed of 200 rpm was observed to range from 600 to 1200 min.