Evaluation and optimization of process parameters on quality features of Al 7075 metal matrix composite during drilling with HSS tool

Abstract Aluminum 7075-based metal matrix composites (MMCs) reinforced with silicon nitride (Si₃N₄) particles offer improved mechanical and tribological properties but present significant machining challenges due to the abrasive nature of ceramic reinforcements. This study investigates the drilling machinability of stir-cast Al7075/Si₃N₄ MMCs containing 2.5, 5, and 7.5 wt% reinforcement. The effects of drill diameter, spindle speed, feed rate, and reinforcement percentage on surface roughness and circularity were evaluated using a Taguchi design of experiments. Hardness increased with increasing Si₃N₄ content due to enhanced load transfer and restriction of plastic deformation caused by hard ceramic particles. Optimization results indicated that reinforcement percentage strongly influenced surface roughness through increased abrasive interaction at the tool–workpiece interface, while spindle speed primarily affected circularity due to its influence on tool stability and dynamic cutting behavior. Optimal conditions for minimum surface roughness were obtained at 7.5 wt% Si₃N₄, 8 mm drill diameter, 1160 rev/min spindle speed, and 0.125 mm/rev feed rate, whereas improved circularity was achieved at 7.5 wt% Si₃N₄, 6 mm drill diameter, 300 rev/min spindle speed, and 1.25 mm/rev feed rate. Grey–Taguchi multi-response optimization was employed to simultaneously minimize surface roughness parameters (Ra, Rz, and Rz max), identifying reinforcement percentage as the dominant factor and yielding optimal drilling conditions of 5 wt% Si₃N₄ reinforcement, 6 mm drill diameter, 1160 rpm spindle speed, and 0.125 mm/rev feed rate for improved hole quality. The developed model demonstrated acceptable predictive capability, reflecting inherent variability associated with machining heterogeneous composites. The findings provide practical guidance for optimizing drilling parameters and improving hole quality in Si₃N₄-reinforced Al7075 composites. The statistically derived parameter ranges may assist preliminary process selection for aerospace and industrial applications, although validation under specific industrial conditions remains necessary. These results are intended to support preliminary process selection and require validation under specific industrial conditions prior to implementation.