Study on the reaming process of aluminum alloy 7050-T7451 under different cooling conditions

Abstract

Aluminum alloy 7050 is widely used in the aeronautical industries. However, owing to their highly ductile property, chips created during high-speed machining cannot be naturally broken, and long continuous chips are unavoidably formed, impacting the machining stability and quality of the parts. Because a smaller cutting allowance is required compared with conventional machining operations, the behavior of the chips during reaming operation may be more complex and different from those determined in previous investigations. Therefore, studying the characteristics of chip formation and hole quality during the reaming process is essential to improve the machinability of aluminum alloy 7050. In this study, three different cooling conditions were applied to reaming aluminum alloy 7050-T7451 with polycrystalline diamond (PCD) reamers. The finite element models (FEMs) were established to simulate the chip formation. The macro- and micro-morphologies of chips under the three cooling conditions were compared to analyze the chip behaviors. The diameter, surface roughness, and micro-morphologies of the reamed holes were also analyzed to evaluate the hole quality. The results showed that the chip morphology was strongly influenced by the cutting parameters and cooling strategies. It was found that the desired chip morphologies, satisfactory geometrical accuracy and surface quality during the reaming of aluminum alloy 7050-T7451 could be achieved using internal cooling at a spindle speed of 8 000 r/min and a feed rate of 0.01 mm/z. This study also demonstrates the feasibility of an internal cooling strategy for breaking chips when reaming aluminum alloy 7050-T7451, which opens new possibilities for improving the chip-snarling that occurs during hole machining.

Keywords

Chip morphology / Hole quality / Cooling conditions / Reaming / Aluminum alloy 7050-T7451 / Finite element model (FEM)