Furthermore. Ramulu and Taya stated that the MRR of silicon carbide whiskers (SiCw) compound materials varied according to the volume fraction of second-phase SiCw. We investigated the effect of spheroidal graphite heterogeneous second phase on the EDM characteristics of Fe-based materials. The variations in second-phase particles significantly increased A/AW values.12-131 This study used a range of 4-29 mass% to change the silicon content in Al-Si alloy specimens: to clarify the effect of heterogeneous second phase on MRR values, and to explore the influence of the area fraction of eutectic silicon particles and primary silicon particles on the EDM characteristics of Al-Si alloys.