The effect of pre-ageing and addition of copper on the precipitation behaviour in Al-Mg-Si alloys

Conference item

Hardness measurements and 3-dimensional atom probe analysis have been used to characterise the precipitation behaviour in two 6xxx series aluminium alloys, one Cu-free alloy (Al-0.78at%Mg0.68at%Si) and one Cu-containing alloy (Al-0.78at%Mg-0.68at%Si-0.30at%Cu). The heat treatments consisted of either natural ageing or pre-ageing at 353K followed by a paint-bake treatment at 453K. Natural ageing was seen to increase the hardness, and hence reduce formability compared to pre-ageing. In addition, the strengthening effect of artificial ageing was less after natural ageing than after pre-ageing. In the Cu-ftee alloy, needle-like beta" was observed to form only after a pre-ageing treatment during the first 60 minutes of a paint-bake treatment. In the Cu-containing alloy, needle-like beta" formed during paint bake in both the naturally-aged and pre-aged material, although it is formed more rapidly after pre-ageing. This was accompanied by an increase in strength over the Cu-ftee alloy and indicates that Cu reduces the deleterious effect of natural ageing.

Authors: Morley, A; Zandbergen, M; Cerezo, A; Smith, G

• Publication status: Published
• Journal: ALUMINIUM ALLOYS 2006, PTS 1 AND 2
• Volume: 519-521
• Pages: 543-548
• Publication date: 2006-01-01
• Event title: 10th International Conference on Aliminium Alloys (ICAA-10)
• ISSN: 0255-5476
• ISBN: 0878494081
• Keywords: Al-Mg-Si alloys; pre-ageing; precipitation hardening; cluster compositions; copper addition; atom probe analysis