Studi Eksperimental Penambahan Variasi Tembaga dan Variasi Media Pengdingin pada Logam Al-Si terhadap Sifat Mekanik dan Mikrostruktur Pengaplikasian Roda Gigi

Abstract

This study investigates the effects of copper addition (8%, 10%, 12%) and cooling media variation (air, SAE 40 oil, water) on the mechanical properties and microstructure of sand-cast Al-Si alloy for gear transmission applications. A factorial experimental design was employed with independent variables of Cu composition and cooling media, while dependent variables included Vickers hardness (ASTM E92), Charpy impact toughness, density (Archimedes method), and microstructure analysis. Key findings reveal Copper Influence is Hardness increased linearly with Cu content (253.3 VHN at 12% Cu) due to Al₂Cu intermetallic phase formation, but accompanied by reduced impact toughness (from 0.0331 J/mm² to 0.0217 J/mm²). Cooling Media Effects Water quenching achieved peak hardness (266.3 VHN) but lowest impact toughness (0.0217 J/mm²), while air cooling yielded more ductile structures with optimal density (2.78 g/cm³). Microstructural Analysis is Quenching caused heterogeneous Al₂Cu distribution with localized porosity, whereas air cooling produced more homogeneous phase distribution. The optimal combination was found in Al-Si-10%Cu with oil cooling, demonstrating balanced properties (196.3 VHN hardness and 0.025 J/mm² impact toughness). However, these results remain below industrial standards for motorcycle gear applications (>250 VHN). The study suggests