Machinability investigation on CNC milling of recycled short carbon fiber reinforced magnesium matrix composites

This study investigates the machinability of magnesium matrix composites reinforced with short carbon fibers, which represent novel materials in the field. AZ91 alloy and its composites containing 2.5 and 5 wt.% recycled carbon fiber (rCF) reinforcements were used as workpieces. Face milling was conducted using uncoated carbide cutting tools under dry cutting conditions with varied cutting speeds (480-560-640 m/min) and feed rates (0.65-0.8-0.95 mm/min). The experimental design was based on the Taguchi L9 (33) orthogonal array. Analysis included cutting forces, surface roughness, wear on cutting inserts, and chip morphology to assess machinability. Taguchi, analysis of variance, and regression methods were employed to analyze cutting force and surface roughness results. Findings indicated satisfactory machinability for AZ91 alloy and comparatively poorer performance for 5 wt.% rCF reinforced composite, with increased reinforcement content correlating with higher cutting force and surface roughness. SEM and EDX analyses revealed significant built-up layer formation on cutting inserts, with predominantly spiral-shaped continuous chips observed in the experiments. Overall, the study affirmed the machinability of the composites and identified suitable cutting parameters for further investigations.