Influence of Copper Content on 6351 Aluminum Alloy Machinability

The main purpose of this work is to study the influence of copper content (Cu) in machining of 6351 aluminum alloy (Al-Si-Mg). The machinability was evaluated from measurements of drilling torque and drilling thrust force in cutting tool and surface roughness of the machined surface during drilling process. Samples of 6351 aluminum alloy were produced with different levels of copper (Cu) (0.07, 0.23, 0.94, 1.43 and 1.93%). Cutting speed and feed rate were varied in five levels (60 to 100 m/min and 0.1 to 0.3 mm/rev). The results showed that increasing the copper content in a Al-Si-Mg-Cu aluminum alloy increase the precipitation hardening through the stabilization of hardening phases like Al5Cu2Mg8Si6 and Al2Cu, also the increase in amount of Al2Cu. Thus, the samples of 6351 aluminum alloy with higher copper content, in general, showed higher hardness and ultimate tensile strength values, while the percentage elongation after fracture was lower. The drilling torque and drilling thrust force during drilling process increased almost linearly with feed rate increase. The samples with higher amount of copper (1.43% and 1.93%) led to higher drilling torque and drilling thrust force for feed rate over than 0.2 mm/rev. Although, the surface finishing of these samples machined holes was slightly worst.