Research on the machinability of SiC reinforced AlSi7Mg2 metal matrix composite materials

SiC reinforced aluminum matrix composites (AMCs) are used in many application areas thanks to their low weight, high specific strength, high specific hardness, high wear resistance, low coefficient of thermal expansion, good dimensional stability, and controllable mechanical properties. Although these composites have superior mechanical and physical properties, the high hardness and high wear resistance, which are inherent properties of SiC particles, lead to low tool life and poor surface quality in the machining of AMCs. This situation limits the applicability and usability of SiC reinforced AMCs. In this study, a series of experimental studies were carried out to investigate the machinability of metal matrix composites (MMCs). In the experimental study, 15% by weight SiC reinforced AlSi7Mg2 composites were drilled using tungsten carbide (WC), AlTiN coated WC and high speed steel (HSS) drills at three different feed rates and rotation speeds. Drilling experiments were carried out in a dry environment. Cutting force and moment, diameter change, burr formation, surface roughness, chip morphology and tool wear were investigated depending on drilling parameters. In addition, the relationship of cutting forces and moments with tool wear was analyzed. Scanning electron microscopy (SEM) was used for chip morphology and tool wear. The cutting force and moment, diameter change, burr height and surface roughness were observed to increase with increasing feed rate. The increase in the rotation speed increased the burr height, decreased the cutting force and moment, diameter change and surface roughness. Among WC, AlTiN coated WC and HSS drills, the best machinability results were obtained with AlTiN coated WC drills, and the worst with HSS drills. In the machining of composite materials, changes in chip structures were occurred depending on the parameters. It has been observed that the chip diameters formed at low rotation speed and feed rate are lower. As the feed rate increased, the chip diameters increased, and the chip structures deteriorated. The presence of micro-scale fractures, cracks, interstices, and fine cavities on the chip surfaces were noted. Micro-sized saw tooth formations were observed on the free surfaces of the chips. In the tool wear analysis, it was seen that the cutting force and moment on the cutting tools and the tool wear increased depending on the increasing number of holes. Higher deformation and wear were observed in the cutting tool exposed to higher cutting force and moment.