Cluster hardening in Al-3Mg triggered by small Cu additions

• Published in: Acta materialia Vol. 161; pp. 12 - 20
• Main Authors: Medrano, S., Zhao, H., De Geuser, F., Gault, B., Stephenson, L.T., Deschamps, A., Ponge, D., Raabe, D., Sinclair, C.W.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.12.2018; Elsevier
• Subjects: Aluminum alloys; Atom probe; Condensed Matter; Materials Science; Physics; Precipitation; Yield strength; Aluminum alloys; Yield strength; Precipitation; Atom probe; yield strength; atom probe; aluminum alloys
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2018.08.050

The aging response of two Al-3Mg alloys with Cu addition <1 wt% has been tracked under simulated automotive paint bake conditions (∼ 20 min, 160 and 200 °C) to quantify the processes controlling hardening. The decomposition of the solid solution, observed by atom probe tomography, has been interpreted using a novel pair correlation function approach and incorporated into a model for prediction of precipitation hardening. It is shown that the hardening is controlled by clusters/Guinier-Preston-Bagaryatsky (GPB) zones similarly to what has been previously observed in much higher Cu containing 2XXX-series alloys. Interestingly, it is shown that very small additions of Cu (< 0.1 at%) can be used to catalyze a high number density of strengthening particles owing to the high enrichment in Mg compared to particles found in more conventional high Cu/low Mg alloys. This allows hardening during the first hour of aging that is as high as that obtainable in these high Cu alloys. [Display omitted]