Accordingly, some molten metal was flushed away with kerosene while some -A1 was not flushed away from silicon particles, due to the low melting point and flooding of the latter, yielding ridges on the EDMed surface. Measuring the composition with Energy dispersive spectrometer (EDS) reveals that the silicon content in ridges greatly exceeds that in the microstructure (Fig. 13), and in some molten A1 coated on eutectic and primary silicon particles. Therefore discharge density is linearly related to ridge den¬sity.