Structures in grain-refined directionally solidified hypoeutectic Al-Cu alloys: Benchmark experiments under microgravity on-board the International Space Station

Materialia, vol. 36, pp. 102171

Abstract

Benchmark solidification experiments were successfully performed under microgravity conditions on-board the International Space Station (ISS) within the ESAprogramme CETSOL (Columnar-to-Equiaxed Transition in SOLidification Processing). Cylindrical samples of grain-refined Al-4wt.%Cu, Al-10wt.%Cu and Al-20wt.%Cu alloys were directionally solidified in a gradient furnace to investigate columnar and equiaxed dendritic growth structures as well as the columnar to equiaxed transition under diffusive conditions. The determination of temperature gradients; interface velocities; and cooling rates at liquidus, solidus, and eutectic front positions provides well-defined thermal experimental characterization. The evaluation of the flight samples demonstrates that no significant macrosegregation along the sample axis occurred and no radial effects were observed. Therefore, purely diffusive solidification behaviour without any residual melt convection can be assumed for these microgravity experiments. The analyses of the microstructure in longitudinal cross-sections show dendritic structures without any pore formation and the averaged eutectic fraction is largely constant along the sample. The samples of refined Al-4wt.%Cu alloy show a sharp CET from columnar dendrites to a fine equiaxed steady-state grain structure whereas in the samples of refined Al-10wt.%Cu and Al-20wt.%Cu alloy, only equiaxed dendritic grain growth is observed. A quantitative analysis of the equiaxed grain morphology shows, that the shapes of the equiaxed dendrites depend on the applied temperature gradient, but the grain sizes in radial and longitudinal directions are identical. Therefore, a fully equiaxed dendritic growth structure without dendrite elongation was obtained. Compared to experiments in microgravity with non-refined Al-Cu alloys the average equiaxed grain size is about three times smaller.

Authors 13

1. László Sturz Aachen Access e.V

   Access

   Affiliation as printed

   ACCESS e.V., Intzestraße 5, 52072 Aachen, Germany

2. C. Pickmann Aachen Access e.V

   Access

   Affiliation as printed

   ACCESS e.V., Intzestraße 5, 52072 Aachen, Germany

3. Elke Schaberger-Zimmermann Aachen Foundry Institut

   RWTH Aachen University

   Affiliation as printed

   Foundry Institut, RWTH Aachen University, Intzestraße 5, 52072 Aachen, Germany

4. András Roósz

   University of Miskolc

   Affiliation as printed

   HUN-REN-ME Materials Science Research Group, 3515 Miskolc, Hungary

   Institute of Physical Metallurgy, Metal Forming and Nanotechnology (UM), University of Miskolc, H3515 Miskolc, Hungary

5. Arnold Rónaföldi
6. Zsolt Veres

   University of Miskolc

   Affiliation as printed

   HUN-REN-ME Materials Science Research Group, 3515 Miskolc, Hungary

   Institute of Physical Metallurgy, Metal Forming and Nanotechnology (UM), University of Miskolc, H3515 Miskolc, Hungary

7. Charles‐André Gandin

   Centre de Mise en Forme des Matériaux

   Affiliation as printed

   CEMEF - Centre de Mise en Forme des Matériaux (Rue Claude Daunesse CS 10207 06904 Sophia Antipolis cedex - France)

8. G. Reinhart

   Institut des Matériaux, de Microélectronique et des Nanosciences de Provence

   Affiliation as printed

   IM2NP - Institut des Matériaux, de Microélectronique et des Nanosciences de Provence (Faculté des Sciences Avenue Escadrille Normandie Niemen Case 142 13397 Marseille Cedex 20 - France)

9. Henri Nguyen-Thi

   Institut des Matériaux, de Microélectronique et des Nanosciences de Provence

   Affiliation as printed

   IM2NP - Institut des Matériaux, de Microélectronique et des Nanosciences de Provence (Faculté des Sciences Avenue Escadrille Normandie Niemen Case 142 13397 Marseille Cedex 20 - France)

10. Nathalie Mangelinck‐Noël

    Institut des Matériaux, de Microélectronique et des Nanosciences de Provence

    Affiliation as printed

    IM2NP - Institut des Matériaux, de Microélectronique et des Nanosciences de Provence (Faculté des Sciences Avenue Escadrille Normandie Niemen Case 142 13397 Marseille Cedex 20 - France)

11. Shaun McFadden

    University of Ulster

    Affiliation as printed

    School of Computing, Eng & Intel. Sys, Ulster University, Northern Ireland, UK Londonderry, United Kingdom

12. Gerd‐Ulrich Grün
    Affiliation as printed

    Speira GmbH, Georg-von-Boeselager-Straße 21, 53117 Bonn, Germany

13. Wim H. Sillekens

    European Space Agency · European Space Research and Technology Centre

    Affiliation as printed

    European Space Agency -ESTEC, Keplerlaan 1 Postbus 299, 2200 AG Noordwijk, the Netherlands