The effect of milling time on the alumina phase transformation in the AMCs powder metallurgy reinforced by silica-sand-tailings

This study aims to determine the effect of milling time and sintering temperature parameters on the alumina transformation phase in the manufacture of Aluminium Matrix Composites (AMCs) reinforced by 20 % silica sand tailings using powder metallurgy technology. The matrix and fillers use waste to make the composites more efficient, clean the environment, and increase waste utilization. The milling time applied to the Mechanical Alloying (MA) process was 0.5, 6, 24, 48, and 96 hours, with a ball parameter ratio of 15:1 and a rotation of 93 rpm. Furthermore, hot compaction was carried out using a 100 MPa two-way hydraulic compression machine at a temperature of 300 °C for 20 minutes. The temperature variables of the sintering parameter process were 550, 600 to 650 °C, with a holding time of 10 minutes. Characterization of materials carried out included testing particle size, porosity, X-Ray Diffraction (XRD), SEM-Image, and SEM-EDX. The particle measurement of mechanical alloying processed, using Particle Size Analyzer (PSA) instrument and based on XRD data using the Scherrer equation, showed a relatively similar trend, decreasing particle size occurs when milling time was increased 0.5 to 24 hours. However, when the milling time increases to 48 and 96 hours, the particle size tends to increase slightly, due to cold-weld and agglomeration when the Mechanical Alloying is processed. The impact is the occurrence of the matrix and filler particle pairs in the cold-weld state. So, the results of XRD and SEM-EDX characterization showed a second phase transformation to form alumina compounds at a relatively low sintering temperature of 600 °C after the mechanical alloying process was carried out with a milling time on least 24 hour