Development of a New 7xxx Ageing Model


Article Preview

A kinetic model has been developed to simulate the precipitate size distribution and the resulting yield strength during ageing of 7xxx alloys. The η phase is the only one considered. The kinetic model is mean field: precipitates of different sizes see each other through the average solid solution. Precipitates are assumed to be homogeneous in concentration and are allowed to change chemistry. Local equilibrium is assumed at the matrix-precipitate interface; the equilibrium concentrations are corrected by the curvature effect. Values of the equilibrium concentrations at the matrix-precipitate interface are solved by an iterative method: the resulting flux for each element must be compatible with equilibrium conditions and with the changing stoechiometry of the considered precipitate while maximizing the energy gained. The yield strength is derived from the precipitate size distribution through a mixture law combining the effect of each individual precipitate. The model can take into account non-isothermal treatments and can therefore simulate complicated multi-stage ageing treatment as well as a FSW weld. Results of the model are discussed and compared measurements.



Materials Science Forum (Volumes 519-521)

Edited by:

W.J. Poole, M.A. Wells and D.J. Lloyd




C. Sigli "Development of a New 7xxx Ageing Model", Materials Science Forum, Vols. 519-521, pp. 321-326, 2006

Online since:

July 2006





[1] R. Wagner and R. Kampmann, Homogeneous Second Phase Precipitation, in Phase Transformations in Materials, vol. 5, Materials Science and Technology, P. Haasen, Ed.: VCH, 1991, pp.213-303.

[2] C. Sigli, Nucleation, Growth and Coarsening of Spherical Precipitates in Aluminum Alloys, presented at Aluminum Alloys: Their Physical and Mechanical Properties (ICAA7), Charlottesville, Virginia, USA, (2000).

DOI: 10.4028/

[3] J. D. Robson and P. B. Prangnell, Dispersoid Precipitation and Process Moldelling in Zirconium Containing Commercial Aluminum Alloys, Acta Mater., vol. 49, pp.599-613, (2001).

DOI: 10.1016/s1359-6454(00)00351-7

[4] M. Nicolas and A. Deschamps, Characterization and Modelling of Precipitate Evolution in an Al-Zn-Mg Alloy During Non Isothermal Heat Treatments, Acta Materialia, vol. 51, pp.6077-6094, (2003).

DOI: 10.1016/s1359-6454(03)00429-4

[5] R. Kampmann and R. Wagner, Kinetics of Precipitation in Metastable Binary Alloys - Theory and Application to Cu - 1. 9at%Ti and Ni- 14at%Al, presented at Decomposition of Alloys: the Early Stages, Sonnenberg, Germany, (1983).

DOI: 10.1016/b978-0-08-031651-2.50018-5

[6] A. Dillmann and G. E. A. Meier, A Refined Droplet Approach To The Problem of Homogeneous Neucleation From Vapor Phase, J. Chem. Phys., vol. 94, pp.3872-3884, (1991).

[7] A. Perini, G. Jacucci, and G. Martin, Interfacial Contribution to Cluster Free Energy, Surface Science, vol. 144, pp.56-66, (1984).

DOI: 10.1016/0039-6028(84)90703-9

[8] C. Sigli and P. Guyot, Cluster Dynamics", presented at "Thermodynamics, Microstructure and Plasticity, NATO Advanced Study Institute, (2002).

[9] J. W. Martin, Micromechanisms in particle-hardened alloys: Cambridge University Press, (1990).

[10] C. Sigli, L. Maenner, C. Sztur, and R. Shahani, Phase Diagram, Solidification and Heat Treatment of Aluminum Alloys, presented at Aluminum Alloys: Their Physical and Mechanical Properties (ICAA6), Toyohashi, Japan, (1998).

[11] H. Bakker, Diffusion in Solid Metals and Alloys, vol. 26. Berlin: Springer-Verlag, (1990).

Fetching data from Crossref.
This may take some time to load.