An investigation on the variations occurring during Ni3Al powder formation by mechanical alloying technique

The Ni3Al intermetallic compound with unique properties is widely used especially for high temperature applications such as gas turbines. There are different ways for producing the compound. Among them, high-energy milling technique using a planetary ball mill has been employed for producing nanocrystalline Ni3Al powders. In this research Ni3Al intermetallic was prepared by mixing pure elemental Al and Ni powders. A ball-to-powder weight ratio of 20:1 and rotation speed of 550 rpm in argon atmosphere were considered as the main processing parameters. The milling time ranged from 1 to 55 h. Changes in the phase and microstructure as a function of milling time were investigated using X-ray diffraction analysis and scanning electron microscopy. The results revealed that the formation of nanocrystalline Ni3Al with minimum crystallite size of 5 nm is obtained after 15 h milling. However, further mechanical alloying resulted in increasing grain size. Furthermore, the process efficiency decreased to less than 50% and the lattice strain increased after 55 h mechanical alloying.