Investigation of drilling properties of AA7075/Al2O3 functionally graded materials using gray relational analysis

Abstract

The present paper reports an experimental study on the fabrication and characterization of aluminum-oxide-reinforced functionally graded aluminum composites and optimization of drilling parameters on thrust force and average surface roughness using gray relational analysis. For this purpose, AA7075/Al2O3 functionally graded materials were produced with three layers that have different ratios of Al2O3 via high-temperature isostatic pressing and powder metallurgy method. Hardness behaviors of the layers were determined. Further, microstructural characterizations of the layers were carried out. Functionally graded materials were machined at dry cutting conditions with a 6 mm uncoated cemented carbide drill bit. The drilling experiments were carried out under different conditions such as point angles, helix angles, and feed rates, while the 25 m/min cutting speed was kept constant. The effects of factors on thrust force and surface roughness were evaluated using analysis of variance and gray relational analysis in full factorial experimental design. The minimum thrust force was measured at 221 N in a 140° point angle, 15° helix angle, and 0.075 mm/rev feed rate. Results of the gray relational analysis showed that feed rate was the dominant factor on thrust force and average surface roughness. Consequently, the highest and lowest gray relational grades were obtained at 0.899 and 0.374, respectively.