Design strategy for controlled natural aging in Al–Mg–Si alloys

This study presents a design strategy for Al–Mg–Si alloys to control natural aging. Recently, trace addition of Sn was shown to suppress natural aging for up to two weeks, which was explained by the strong trapping of vacancies to Sn atoms. Here we explore the effect of solution treatment temperatur...

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Bibliographic Details
Published in:Acta materialia 2016-10, Vol.118, p.296-305
Main Authors: Werinos, M., Antrekowitsch, H., Ebner, T., Prillhofer, R., Curtin, W.A., Uggowitzer, P.J., Pogatscher, S.
Format: Article
Language:English
Subjects:
Aging (natural)
Alloys
Aluminum alloys
Clustering
Computer simulation
Copper
Magnesium
Mathematical models
Natural aging
Phase transformation kinetics
Trace elements
Vacancies
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Summary:This study presents a design strategy for Al–Mg–Si alloys to control natural aging. Recently, trace addition of Sn was shown to suppress natural aging for up to two weeks, which was explained by the strong trapping of vacancies to Sn atoms. Here we explore the effect of solution treatment temperature, the combination of trace elements such as Sn and In, and the composition of main hardening elements Mg, Si and Cu on natural aging. The results are discussed based on the dissolvable amount of trace elements and their effect on diffusion retardation, and solute clustering mechanisms in Al–Mg–Si alloys. Thermodynamic calculations using the CALPHAD approach show that maximum retardation of natural aging is achievable at the highest trace element solubility, which exists at significantly different solution treatment temperatures for Sn or In. The effects of Mg, Si and Cu content on natural aging kinetics are interpreted via their influence on the Sn solubility and clustering mechanisms. It is proposed that Sn additions reduce the concentration of excess vacancies, which is most important for early Si clustering, and that the effect of Cu is comparable to the effect of Sn, but less pronounced. Based on the investigated parameter space, a design concept is proposed and an Al–Mg–Si alloy showing suppression of natural aging for >6 months and significant artificial aging potential is demonstrated. [Display omitted]
ISSN:1359-6454
1873-2453
DOI:10.1016/j.actamat.2016.07.048