The production of $B_{4}C$ reinforced metal matrix composite from waste $AZ91$ magnesium alloy using the ball milling method

Abstract

In this study, the Mg/$B_4$C composite reinforced with boron carbide particles was produced by mechanical milling method using waste AZ91 magnesium alloy chips. The mechanical and tribological properties of the produced composites were investigated through hardness and wear tests. A mixture of AZ91 magnesium alloy chips, aluminum, and $B_4$C powders was milled at a rotation speed of 300 rpm with a ball-to-powder ratio of 20:1 for 3 hours. The milled powders were first cold pressed and then sintered at 550 °C for 3 hours. In density measurement, it was observed that the sample reinforced with B4C exhibited an increase in density. In X-ray diffraction analysis, peaks corresponding to Mg, $Mg_{17}Al_{12}$, and MgO were detected, while the $B_4$C phase could not be identified. On the other hand, $B_4$C particles in the microstructure were revealed in the energy dispersive X-ray spectroscopy analysis. Scanning electron microscope images revealed that the Mg/$B_4$C composite had lower porosity, consistent with density measurements. It was found that the hardness and wear resistance of the Mg/B4C composite were higher than those of the Mg alloy, which can be attributed to the presence of homogenously distributed hard B4C particles within the microstructure.