Comparative Analysis in Drilling Performance of AA7075 in Different Temper Conditions

Abstract

The widespread use of heat treatable7075 aluminum alloy in the aerospace industry requires a high machinability performance. The main objective of this study is to examine the machinability and the surface quality conditions of the AA7075 material with different temper conditions. For this purpose, various temper treatments are implemented to evaluate the impact of microstructural properties on tool wear and the surface quality of the drilled holes. The drilling operations have been done on O, F, T4, T6, and T7 temper conditions. Process parameters were three different spindle speeds (715, 1520, and 3030 rev/min) and three feed rates (0.1, 0.2, and 0.3 mm/rev) with HSS-G high-performance ground standard twist drill bit. The present work deals with the effects of temper conditions on thrust force, drilling temperature, tool wear, surface integrity, and chip morphology. Response surface methodology was used in the evaluation of experiment results. The optimization results showed that while thrust force and torque are not significantly affected by a change in spindle speed, they are sensitive to an increase in feed rate. Heat-generation on the drill bit is the lowest at low levels of both the feed rate and spindle speed parameters. The AA7075-T6 condition specimen was machined with continuous chip formation, resulting in the best hole surface quality. 3D Finite element modeling of the drilling process was carried out. Numerical analysis revealed the drilling performance of AA7075-T6 in terms of thrust, heat generation and chip formation.