Pengaruh Variasi Waktu Pengadukan Lelehan Aluminium Terhadap Sifat Mekanik dan Mikrostruktur Komposit Aluminium HD2 G2/AlO3 dengan Metode Stir Casting

Abstract

This study investigated the effect of stirring time on the hardness, tensile properties, modulus of elasticity, and microstructure of HD2 G2 aluminum composites reinforced with 5 wt% 𝐴𝑙2 𝑂3and 1 wt% Mg fabricated using the stir casting method. The stirring times were varied at 5, 10, 15, and 20 minutes. Mechanical characterization included Rockwell B hardness and tensile testing, while microstructural analysis was conducted using Scanning Electron Microscopy (SEM) and fracture morphology observations. The results showed that stirring time significantly affected the mechanical properties and microstructure of the composites. The optimum condition was obtained at a stirring time of 10 minutes, which produced the highest hardness of 45.1 HRB, Ultimate Tensile Strength (UTS) of 155.02 MPa, and elongation at break of 2.67%. Meanwhile, the highest modulus of elasticity was obtained at a stirring time of 5 minutes with a value of 2552.78 MPa. SEM observations revealed that the 10-minute stirring time resulted in a more homogeneous distribution of 𝐴𝑙2 𝑂3 particles with fewer porosities and agglomerations. In contrast, longer stirring times increased the formation of porosity and particle agglomeration, leading to a deterioration in the mechanical properties of the composites. Therefore, a stirring time of 10 minutes was concluded to be the optimum condition for producing HD2 G2-𝐴𝑙2 𝑂3 composites with the best overall performance.