Formation of nanostructured weldments in the Al–Si system using electrospark welding

Electrospark welding (ESW) electrodes were manufactured from three binary aluminum–silicon alloys consisting of 12 and 17 wt% silicon, produced using chill and sand casting. The electrodes were used to assess the feasibility of producing aluminum–silicon weldments consisting of nano-sized silicon particles embedded in nanostructured aluminum matrix, using the ESW process. Line 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), atomic force microscopy (AFM), and transmission electron microscopy (TEM) was performed to determine the composition and microstructure of the depositions. It was determined that a capacitance of 110 μF and a voltage of 100 V resulted in the highest quality deposition. Furthermore it was determined that the ESW process was capable of producing a microstructure consisting of an extremely fine-grained silicon phase ranging from ∼6 to 50 nm for the eutectic composition, and 10–200 nm for the hypereutectic compositions. Finally it was determined that the functional thickness limit of the aluminum–silicon deposit produced under these process parameters was 120 μm.