Diffusion-defining atomic-scale spinodal decomposition within nanoprecipitates


Stoichiometric precipitates owe their fixed composition to an ordered crystal structure. Deviations from that nominal value, however, are encountered at times. Here we investigate composition, structure and diffusion phenomena of ordered precipitates that form during heat treatment in an industrially cast Al–Mg–Sc–Zr alloy system. Experimental investigations based on aberration-corrected scanning transmission electron microscopy and analytical tomography reveal the temporal evolution of precipitate ordering and formation of non-equilibrium structures with unprecedented spatial resolution, supported by thermodynamic calculations and diffusion simulations. This detailed view reveals atomic-scale spinodal decomposition to majorly define the ongoing diffusion process. It is illustrated that even small deviations in composition and ordering can have a considerable impact on a system’s evolution, due to the interplay of Gibbs energies, atomic jump activation energies and phase ordering, which may play an important role for multicomponent alloys.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1: Structure and composition of short-aged and long-aged precipitates.
Fig. 2: Analysis of radial compositional variation of a precipitate in a long-aged EBRS-treated sample.
Fig. 3: Comparison of HAADF images and simulations of L12 precipitates with different numbers of Al atoms on Sc sites.
Fig. 4: Gibbs free energy calculations.
Fig. 5: Results of 3D atomistic diffusion simulation showing the evolution of diffusion channels.

Data availability

The data sets generated and/or analysed during the current study as well as any custom code used during this study are available from the authors on reasonable request.


  1. 1.

    Clouet, E. et al. Complex precipitation pathways in multicomponent alloys. Nat. Mater. 5, 482–488 (2006).

  2. 2.

    Hald, J. Prospects for martensitic 12 % Cr steels for advanced steam power plants. Trans. Indian Inst. Met. 69, 183–188 (2016).

  3. 3.

    Danielsen, H. K. Review of Z phase precipitation in 9–12 wt-%Cr steels. Mater. Sci. Technol. 32, 126–137 (2016).

  4. 4.

    Taendl, J., Orthacker, A., Amenitsch, H., Kothleitner, G. & Poletti, C. Influence of the degree of scandium supersaturation on the precipitation kinetics of rapidly solidified Al-Mg-Sc-Zr alloys. Acta Mater. 117, 43–50 (2016).

  5. 5.

    Taendl, J. et al. In-situ observation of recrystallization in an AlMgScZr alloy using confocal laser scanning microscopy. Mater. Charact. 108, 137–144 (2015).

  6. 6.

    Williams, J. C. & Starke, E. A. Progress in structural materials for aerospace systems. Acta Mater. 51, 5775–5799 (2003).

  7. 7.

    Cavanaugh, M. K., Birbilis, N., Buchheit, R. G. & Bovard, F. Investigating localized corrosion susceptibility arising from Sc containing intermetallic Al3Sc in high strength Al-alloys. Scr. Mater. 56, 995–998 (2007).

  8. 8.

    Sawtell, R. R. & Jensen, C. L. Mechanical properties and microstructures of Al-Mg-Sc alloys. Metall. Mater. Trans. A 21, 421–430 (1990).

  9. 9.

    Filatov, Y., Yelagin, V. & Zakharov, V. New Al–Mg–Sc alloys. Mater. Sci. Eng. A 280, 97–101 (2000).

  10. 10.

    Taendl, J., Palm, F., Anders, K., Gradinger, R. & Poletti, C. Investigation of the precipitation kinetics of a new Al-Mg-Sc-Zr alloy. Mater. Sci. Forum 794796, 1038–1043 (2014).

  11. 11.

    Novotny, G. M. & Ardell, A. J. Precipitation of Al3Sc in binary Al-Sc alloys. Mater. Sci. Eng. A 318, 144–154 (2001).

  12. 12.

    Røyset, J. & Ryum, N. Kinetics and mechanisms of precipitation in an Al-0.2wt.% Sc alloy. Mater. Sci. Eng. A 396, 409–422 (2005).

  13. 13.

    Røyset, J. & Ryum, N. Scandium in aluminium alloys. Int. Mater. Rev. 50, 19–44 (2005).

  14. 14.

    Clouet, E., Barbu, A., Laé, L. & Martin, G. Precipitation kinetics of Al3Zr and Al3Sc in aluminum alloys modeled with cluster dynamics. Acta Mater. 53, 2313–2325 (2005).

  15. 15.

    Tolley, A., Radmilovic, V. & Dahmen, U. Segregation in Al3(Sc,Zr) precipitates in Al-Sc-Zr alloys. Scr. Mater. 52, 621–625 (2005).

  16. 16.

    Forbord, B., Lefebvre, W., Danoix, F., Hallem, H. & Marthinsen, K. Three dimensional atom probe investigation on the formation of Al3(Sc,Zr)-dispersoids in aluminium alloys. Scr. Mater. 51, 333–337 (2004).

  17. 17.

    Haberfehlner, G., Orthacker, A., Albu, M., Li, J. & Kothleitner, G. Nanoscale voxel spectroscopy by simultaneous EELS and EDS tomography. Nanoscale 6, 14563–14569 (2014).

  18. 18.

    Allen, L. J., D’Alfonso, A. J. & Findlay, S. D. Modelling the inelastic scattering of fast electrons. Ultramicroscopy 151, 11–22 (2015).

  19. 19.

    Kozeschnik, E. Modeling Solid-State Precipitation (Momentum, New York, 2012).

  20. 20.

    Jones, R. A. L. Soft Condensed Matter (Oxford Univ. Press, Oxford, 2002).

  21. 21.

    Fuller, C. B., Murray, J. L. & Seidman, D. N. Temporal evolution of the nanostructure of Al(Sc,Zr) alloys: Part I-Chemical compositions of Al3(Sc1−xZrx) precipitates. Acta Mater. 53, 5415–5428 (2005).

  22. 22.

    Gubbens, A. et al. The GIF Quantum, a next generation post-column imaging energy filter. Ultramicroscopy 110, 962–970 (2010).

  23. 23.

    Schlossmacher, P., Klenov, D. O., Freitag, B. & von Harrach, H. S. Enhanced detection sensitivity with a new windowless XEDS system for AEM based on silicon drift detector technology. Micros. Today 18, 14–20 (2010).

  24. 24.

    Kramers, H. A. XCIII. On the theory of X-ray absorption and of the continuous X-ray spectrum. Philos. Mag. 46, 836–871 (1923).

  25. 25.

    Azevedo, S. G., Schneberk, D. J., Fitch, J. P. & Martz, H. E. Calculation of the rotational centers in computed tomography sinograms. IEEE Trans. Nucl. Sci. 37, 1525–1540 (1990).

  26. 26.

    Uusimäki, T. et al. Three dimensional quantitative characterization of magnetite nanoparticles embedded in mesoporous silicon: local curvature, demagnetizing factors and magnetic Monte Carlo simulations. Nanoscale 5, 11944–11953 (2013).

  27. 27.

    Leary, R., Saghi, Z., Midgley, P. A. & Holland, D. J. Compressed sensing electron tomography. Ultramicroscopy 131, 70–91 (2013).

  28. 28.

    Saghi, Z. et al. Compressed sensing electron tomography of needle-shaped biological specimens - potential for improved reconstruction fidelity with reduced dose. Ultramicroscopy 160, 230–238 (2016).

  29. 29.

    Simmons, R. O. & Balluffi, R. W. Measurements of equilibrium vacancy concentrations in aluminum. Phys. Rev. 117, 52–61 (1960).

  30. 30.

    Mommaa, K. & Izumia, F. VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data. J. Appl. Crystallogr. 44, 1272–1276 (2011).

Download references


The authors thank the Austrian Cooperative Research Facility, the Austrian Ministry for Transport, Innovation and Technology (project GZ BMVIT- 612.011/0001-III/I1/2015) and the Austrian Research Promotion Agency FFG (TAKE OFF project 839002) for funding. We would like to express our gratitude to F. Hofer for supporting the project and to W. Sprengel for advice concerning the manuscript. Furthermore, we would like to thank L. Allen and his group for support with µSTEM and M. Weyland, J. Etheridge and S. Findlay for support concerning quantitative STEM.

Author information

A.O. performed all STEM investigations including sample preparation for tomography and STEM HAADF simulations, interpreted the results and wrote the bigger part of the manuscript. G.H. provided the software for tomographic alignment and reconstruction and supported its application. J.T. and M.C.P. provided the samples and information and performed the re-solidification and ageing process. B.S. coded the Gibbs energy calculation and the 3D atomistic diffusion simulation and wrote the parts of the manuscript treating them. G.K. supervised the project and the writing of the manuscript.

Correspondence to Angelina Orthacker or Gerald Kothleitner.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary Figures: Supplementary Figures 1–5 Supplementary Reference 1

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Orthacker, A., Haberfehlner, G., Taendl, J. et al. Diffusion-defining atomic-scale spinodal decomposition within nanoprecipitates. Nature Mater 17, 1101–1107 (2018). https://doi.org/10.1038/s41563-018-0209-z

Download citation

Further reading