Experimental study on surface quality of CNTs/Al composites in high-speed ball-end milling

Abstract

Carbon-nanotube–reinforced aluminium (CNTs/Al) composites have emerged as promising candidates for aerospace and defence applications that demand superior component surface integrity, yet its machining window under high-speed ball-end milling remains insufficiently quantified. In this study, a non-uniform finite-element model of high-speed ball-end milling of CNTs/Al composites was developed in ABAQUS. A Box–Behnken design (BBD) response-surface experiments together with single-factor experiments was implemented, and surface morphology, surface roughness, and subsurface defects were characterised using confocal laser scanning microscopy and scanning electron microscopy. This framework elucidates how spindle speed (n), feed rate (v_f), and axial depth of cut (a_p) govern roughness (Ra) and the formation mechanisms of surface defects during high-speed ball-end milling. ANOVA of the BBD response-surface experiments shows that a_p is the dominant factor affecting surface Ra (F = 102.56), followed by n (F = 33.74) and v_f (F = 19.96). Through the three-dimensional simulation model of the machined surface and the laser confocal microscope scanning, it can be seen that the surface defects during milling are burrs, peaks, pits. The main removal forms of CNTs are pull-out, fracture and destruction. In the actual processing, keeping n between 11,000 and 13,000 r/min, v_f between 8 and 12 mm/min, and a_p below 10 mm yields better surface quality while maintaining machining efficiency.