Machinability of aluminum 7075 alloys

Abstract

This study delves into the dry and wet end milling of three distinct Aluminum 7075 alloys: AL7075, AL7075 – Sc (with a 0.1% Sc addition), and AL7075 – Sc – Li (featuring a 0.1% Sc and 2.2% Li addition). The primary objective is to explore how cutting parameters (cutting speed and feed rate), heat treatment, alloy composition, and cooling methods influence three key machinability factors: surface roughness, cutting force, and particle emission. In the initial phase of the investigation, all three alloys underwent heat treatment at five different aging times and temperatures. Subsequently, the machining process focused on the alloys' hardest and softest conditions achieved through these heat treatments, aiming to analyze the impact of hardness on machinability. The second phase involved end milling using the same tool and a consistent depth of cut under both dry and wet conditions. This was done to scrutinize the effects of feed rate, cutting speed, and cooling methods on the specified machinability criteria. The study employed a multi-level experimental approach to generate machining results, which would then undergo statistical analysis. The results in the heat treatment process showed that between all alloys, 24-hour heat treatment at 120°C leads to highest hardness and in contrast the lowest hardness values were observed in both single aging (8 hours at 280°C) and double aging (8 hours at 280°C followed by 24 hours at 120°C) that underscores the primary role of aging temperature in influencing alloy hardness and strength, regardless of whether the aging process is single or double. The machining results illustrated that in all three alloys used in our study, the feed rate had the most significant effect on surface roughness (Ra). The cutting speed and higher hardness had negative effect on surface quality. The results also revealed that feed rate is the most significant affective parameter on cutting force. Wet machining significantly reduces cutting force, and this reduction is relatively more when machining hard alloys. It was also evident that higher hardness results in increased cutting force in all three alloys. In this study cutting speed did not show significant effect on the cutting force. Particle emission was significantly affected when using cutting fluid. Cutting speed was the second significant effective parameter on particle emission.

Date	5 Mar 2024
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Victor Songmene (Supervisor) & Fawzy Hosny Samuel (Co-supervisor)