Variation characteristics of machinability in drilling of SiC particle reinforced aluminum matrix (SiCp/Al) composite with a wide range of particle volume fractions

Particle reinforced aluminum matrix (SiCp/Al) composite has been one of the promising engineering materials due to its excellent mechanical and thermal characteristics. However, their poor machinability greatly limits the wide applications due to the existence of hard abrasive particles. This paper contributes to the current literatures by systematically studying the effect of a wide range of particle volume fraction (Pvf) on the machinability in dry drilling of SiCp/Al composites and finding the variation characteristic of machinability for the first time. Specifically, tool wear characteristics, chip formation characteristics, machining damage characteristics including hole entrance, hole exit, hole wall, and particle damage are comprehensively analyzed, and the corresponding formation mechanisms are revealed. Combined with the analysis of variance (ANOVA), the importance of the experimental parameters on machinability indicators is obtained. The results show that Pvf contributes 44.1%, 74.1%, and 74.2% to cutting force, burr height, and surface roughness, respectively, and maintain a strong linear relationship with the three indicators. Chip topography analysis found that C-chip, conical spiral chip, curls chip, and fan chip were under low Pvf, and gradually changed to only fan chip under high Pvf. The burr on the hole exit gradually turns into edge breakage with the increase of Pvf. The main reason for the variation characteristic of machinability is concluded to be the variation of the ductility-brittleness of the materials with increase in Pvf. In addition, microstructural analysis shows that the particle damage characteristics comprise squeezing, debonding, squeezing fracture, and shear fracture.