Micro-drilling of Mg-based MMCs reinforced with SiO₂ nanoparticles: An experimental approach

Mg-based metal matrix composites reinforced with nanoparticles are promising biomaterials due to their biocompatibility and high hardness and because they are local and systemic toxicity free. Nano-metal matrix composites are considered to be hard-to-machine materials due to the high strength and high abrasiveness of the reinforcing nanoparticles. In this article, the micro-drilling mechanisms of Mg-based metal matrix composites reinforced with different volume fraction of SiO₂ nanoparticles (0.5, 1.0, 1.5, 2.0 vol.%) were investigated experimentally. Results obtained were also compared with pure Mg. First, it was found that the volume fraction and drilling parameters played an important role in the chip formation mechanism. Second, the influence of drilling parameters on hole surface morphology and cutting force were studied, in which both the rotation speed and feedrate affected the surface morphology, and the main factor affecting cutting force was found to be the feedrate. Furthermore, the formation of burrs was investigated. The height of the burr could be reduced by using small feedrate and low rotation speed. Finally, the size effect of micro-drilling was studied. The variation of surface roughness and cutting force of pure Mg and Mg-based metal matrix composites had three changing trends with the uncut chip thickness. The minimum chip thickness of Mg/SiO₂ metal matrix composites was determined to be 1.1 μm.