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Factors Affecting the Machinability of Al-Mg-Si Extrusions

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Factors Affecting the Machinability of Al-Mg-Si Extrusions

Jules Kouam, Imed Zaghbani, and Victor Songmene,
École de Technologie Supérieure (ÉTS), Montréal, QC, Canada
Nick Parson and Alexandre Maltais,
Rio Tinto Alcan, Jonquière, QC, Canada

Track: VALUE-ADDED PROCESSES - Metallurgical Factors

ABSTRACT—Extruded Al-Mg-Si sections are often machined to produce value-added finished
components. The productivity and cost of the machining process are a function of several
parameters, including tool life, quality of the machined part, and process parameters such as
cutting speed and feed rate used. The ability to form discontinuous and short chips to facilitate
removal from automated machining lines is also a primary requirement for a machining grade
extrusion. The specific alloy plays a role, and these factors are often combined into a single term
expressed as the alloy’s “machinability”. For the Al-Mg-Si alloy family, the free-machining alloy
AA6262-T6, containing lead and bismuth, is considered the benchmark although its use is
decreasing globally due to legislation associated with lead toxicity. The industry is seeking
alternative alloy formulations with machinability approaching AA6262-T6. The current study
compares the machinability in a non-lubricated drilling mode for alternate Al-Mg-Si alloy
formulations, including AA6262-T6, AA6061-T6 variants and a high silicon, AA4xxx-T6 type
alloy. Comparisons were made in terms of tool wear, cutting force, surface roughness, and burr
formation, over a range of cutting speeds and feed rates. Chip formation was also characterized. It
was found that alloy composition had a significant impact on machining force and on tool
performance. Chip formation was mainly controlled by cutting speed, but was also influenced by
the type of alloy.

© Extrusion Technology for Aluminum Profiles Foundation (ET Foundation). All rights reserved. No part of The Proceedings may be reproduced in any form without the express written permission of the ET Foundation.