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

S. Medrano (1) , H. Zhao (2) , Frédéric de Geuser (3) , B. Gault (2) , L. T. T Stephenson (2) , A. Deschamps (3) , D. Ponge (2) , D. Raabe (2) , C. W. W Sinclair (1)

1 UBC - University of British Columbia
2 Max-Planck-Institut für Eisenforschung GmbH
3 SIMaP - Science et Ingénierie des Matériaux et Procédés

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 (< 0.1at%) 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.

Mots clés: Precipitation; aluminum alloys; yield strength; atom probe

Domaines: Science des matériaux [cond-mat.mtrl-sci]

S. Medrano, H. Zhao, Frédéric de Geuser, B. Gault, L. T. T Stephenson, et al.. Cluster hardening in Al-3Mg triggered by small Cu additions. Acta Materialia, 2018, 161, pp.12 - 20. ⟨10.1016/j.actamat.2018.08.050⟩. ⟨hal-01869035v2⟩