Comparative Analysis in Drilling Performance of AA7075 in Different Temper Conditions

Abstract

AA7075 is one of the most suitable materials for aerospace, aircraft, and defense applications with its high yield strength and low-density. In many other modern machining methods, conventional drilling remains the most extensive material removal process in industrial components. The main objective of this study is examining the machinability and 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 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. Drilling performance is related to the intrinsic microstructural properties of temper conditions. 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 change in spindle speed, they are sensitive to 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. Among different temper conditions, the AA7075-T6 condition sample is processed with continuous chip formation and resulted in the best hole surface quality. The 3D finite element modelling of the drilling process was carried out, and the drilling performance of AA7075-T6 was evaluated in terms of thrust force, heat generation, and chip formation.