Analisa Pengaruh Pengecoran Al Scrap-Mg Menggunakan Sand Mold dan Permanent Mold Terhadap Sifat Mekanik dan Mikrostruktur sebagai Material Alternatif pada Pembuatan Rumah Roler Vario 125

Abstract

This study aims to analyze the effect of adding 4% magnesium to aluminum scrap on the mechanical properties and microstructure of cast products using two different casting methods, namely sand mold and permanent mold, as an alternative material for manufacturing the roller housing of the Honda Vario 125 motorcycle. The experimental method was conducted by casting Al–Mg alloys at a pouring temperature of 780°C, followed by mechanical testing including the Brinell hardness test, wear test, impact test, and microstructural observation using an optical metallurgical microscope. The results showed that the specimen cast using the sand mold method had the highest average hardness value of 72.416 BHN, while the permanent mold specimen had a hardness of 67.608 BHN. However, in terms of toughness, the permanent mold specimen exhibited a higher impact energy (0.0296 J/mm²) compared to the sand mold specimen (0.0263 J/mm²). The wear test results indicated that the permanent mold specimen had better wear resistance with a wear rate of 1.227 × 10⁻⁸ mm³/Nmm compared to 2.816 × 10⁻⁹ mm³/Nmm for the sand mold specimen. Microstructural observations revealed that the permanent mold casting produced a finer, denser, and more homogeneous grain structure with a uniform distribution of magnesium, whereas the sand mold casting exhibited coarser grains, nonuniform magnesium distribution, and higher micro-porosity. Therefore, the addition of magnesium to aluminum scrap significantly improves mechanical properties and microstructural quality, particularly when processed using the permanent mold method, making it a potential alternative material for roller housing components in motorcycles