Development of a nanostructure microstructure in the Al–Ni system using the electrospark deposition process

Electrospark deposition (ESD) was applied to produce aluminum–nickel coatings consisting of nanostructured Al and Al3Ni phases. An ESD electrode was manufactured from a hypo-eutectic aluminum–Al3Ni alloy using chill casting. Line deposition tests were performed to determine the optimal processing parameters resulting in a high quality deposit. X-ray diffraction (XRD) as well as optical and field emission scanning electron microscopy (FE-SEM), were performed to determine the composition and microstructure of the resulting depositions. It was determined that a capacitance of 20 μF and a voltage of 100 V resulted in the highest quality deposition. Furthermore it was determined that the ESD process was capable of producing a microstructure consisting of highly refined aluminum and Al3Ni phases. The grain size of the aluminum phase was calculated, through the application of the Scherrer equation, to be ∼25 nm. While, via scanning electron microscopy the grain size of the Al3Ni phase was determined to be ∼44 nm. Also it was determined that multiple deposition passes resulted in increasing the thickness of the deposit, however resulted in decreased deposit quality. Furthermore, it was determined that increasing the energy-density (pulse-energy divided by electrode cross-sectional area) resulted in increasing deposit thickness, until a maximum was obtained using an energy-density of ∼0.8 J/mm2. However, increasing the energy-density beyond this point resulted in decreased deposit quality.