Coating of Al substrate by metallic Ni through mechanical alloying

Aluminum alloy substrate was coated by nickel powder using mechanical alloying (MA) method. Aluminum samples, which were ball-milled with nickel powder in a planetary ball-mill, were in the cubic form with 1 cm × 1 cm × 1 cm dimensions. During the mechano-activation processing, the substrate surface was impacted by some flying balls along with particles of powder. The substrate surface was hardened and activated as a result of the high-energy impact of balls. Ni–Al intermetallic phases were formed in the coating layer. Formation of such intermetallic phase increases the local temperature. The increased temperature causes a better adherence of the nano-sized coating to the substrate. Coated samples were annealed at 550 °C for 330 min. The measurements of Vickers microhardness were performed on both substrate and coating. The microstructure of samples was investigated by scanning electron microscopy (SEM) and optical microscope. Chemical composition was analyzed by energy dispersive X-ray spectroscopy (EDS). The final structure was studied by X-ray diffraction (XRD) analysis. Transmission electron microscopy (TEM) was also used to observe coating particles.