Precipitation in Al-Alloy 6016 – The Role of Excess Vacancies

Abstract:

6xxx Al alloys owe their superior mechanical properties to the precipitation of finely dispersed metastable β´´ precipitates. These particles are formed in the course of optimized heat treatments, where the desired microstructure is generated in a sequence of precipitation processes going from MgSi co-clusters and GP zones to β´´ and β´ precipitates and finally to the stable β and Si diamond phases. The entire precipitation sequence occurs at relatively low temperatures (RT to approx. 200 °C) and is mainly controlled by the excess amount of quenched-in vacancies, which drive the diffusional processes at these low temperatures. Very recently a novel model for the prediction of the excess vacancy evolution controlled by the annihilation and generation of vacancies at dislocation jogs, grain boundaries and Frank loops was developed and implemented in the thermo-kinetic software MatCalc. In the present work, we explore the basic features of this model in the simulation of the excess vacancy evolution during technological heat treatments. The focus of this article lies on the effect of vacancy supersaturation during different heat treatment steps, such as quenching, heating, natural and artificial aging.

• Periodical: Materials Science Forum (Volumes 706-709)
• Pages: 317-322
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.706-709.317
• Online since: January 2012
• Authors: Ahmad Falahati, Peter Lang, Ernst Kozeschnik
• Keywords: Aging, Al-Mg-Si Alloy, Annihilation, Kinetic, Precipitation, Vacancy

References

[1] R. Vissers, M. A. van Huis, J. Jansen, H. W. Zandbergen, C.D. Marioara, S.J. Andersen: Acta Mater. 55 (2007), p.3815.

DOI: 10.1016/j.actamat.2007.02.032

[2] C. Wolverton: Acta Mater. 55 (2007), p.5867.

[3] M. A. van Huis, M. H. F Sluiter, J. H. Chen, H. W. Zandbergen: Phys. Rev. B 76, 174113 (2007).

[4] T. Sato, S. Hirosawa, K. Hirose and T. Maeguchi: Metall. Mater. Trans. Vol. 34A (2003), p.2745.

[5] J. Banhart, M.D.H. Lay, C.S.T. Chang, A.J. Hill: Physical Review B, Vol. 83 (2011), p.014101.

[6] S. Pogatscher, H. Antrekowitsch, H. Leitner, T. Ebner, P.J. Uggowitzer: Acta Mater, (2011), in print.

[7] C. S. T. Chang, I. Wieler, N. Wanderka, J. Banhart: Ultramicroscopy 109 (2009), p.585.

[8] J. D. Bryant: Metall Mater Trans A , Vol. 30, (1999), p. (1999).

[9] S. Esmaeili, D.J. Lloyd, W.J. Poole: Acta Materialia, 51 (2003), p.3467.

[10] H.S. Zurob, H. Seyedrezai: Scripta Materialia, 61(2009), p.141.

[11] F.D. Fischer, J. Svoboda, F. Appel, E. Kozeschnik: Modelling of Excess Vacancy Annihilation at Different Types of Sinks. Acta Materialia, (2011) in print.

DOI: 10.1016/j.actamat.2011.02.020

[12] http: /www. matcalc. at.

[13] R.W. Cahn, P. Haasen: Physical metallurgy, Fourth, revised and enhanced edition Vol. 2, Elsevier Science B.V. (1996).

[14] A. Falahati, E. Povoden-Karadeniz, P. Lang, P. Warczok, E. Kozeschnik: Int. J. Mater. Res. Vol. 101 (2010), p.1089.

[15] Thermodynamic database for Al-Systems, (mc_al_v0. 022. tdb), Institute of Materials Science and Technology, Vienna University of Technology, Austria.

[16] Mobility database for Al-Systems, (mc_al_v1. 015. pdb), Institute of Materials Science and Technology, Vienna University of Technology, Austria.

[17] K.G.F. Janssens, D. Raabe, E. Kozeschnik, M.A. Miodownik, B. Nestler: Elsevier Academic Press (2007).

[18] E. Kozeschnik, J. Svoboda, P. Fratzl, F.D. Fischer: Mater. Sci. Eng. A. 385 (2004) 157.

[19] H.S. Hasting, A.G. Frøseth, S.J. Andersen, R. Vissers, J.C. Walmsley, C.D. Marioara, F. Danoix, W. Lefebvre, R. Holmestad: J. Appl. Phys. 106 (2009), p.123527.

DOI: 10.1063/1.3269714