Type of presentation: Poster

MS-4-P-2525 Multi-Scale-Analysis of Modern Aluminium-Alloys

Schroettner H.^{1, 2}, Panzirsch B.³, Albu M.², Mitsche S.^{1, 2}, Mertschnigg S.^{1, 2}, Gspan C.², Rattenberger J.², Wagner J.², Hofer F.^{1, 2}

¹Institute for Electron Microscopy and Nanoanalysis (FELMI), Steyrergasse 17, 8010 Graz, Austria, Graz University of Technology (TU Graz), ²Graz Centre for Electron Microscopy (ZFE), Steyrergasse 17, 8010 Graz, Austria, ³Austrian Foundry Research Institute (OGI), Parkstraße 21, 8700 Leoben, Austria

hartmuth.schroettner@felmi-zfe.at

During the last years a lot of new light metal alloys for automotive and aerospace applications have been developed. Most of them have been generated based on practical experience. So there is a demand for a deeper insight of the inner structure and the resulting mechanical properties of these materials. In this project four Austrian institutes (OFI, OGI, SZA, ZFE) – all members of the Austrian Cooperative Research (ACR) – are focusing their knowledge and efforts to receive a holistic view of these materials.

Heat resistant aluminium-alloys possess good creep strength and high thermal stability and can be used for permanent casting. Their strength properties are based on specific precipitations in the

structure of the materials.

The main goal of this project is to characterise the fundamental mechanism, which affect the high temperature strength and the creep strength, the connectivity and the corrosion resistance. Based on these findings an optimization of these alloys should be achieved.

The focus of this work is the multi-scale-analysis of the structure of modern aluminium-cast-alloys. Classical metallography is combined with micro- and nano-characterisation methods using scanning electron microscopy (SEM) (Fig. 1) and transmission electron microscopy (TEM) as well as 3D-methods as computer-tomography (CT) and in-situ-ultramicrotomy (3viewTM) [1] (Fig. 2) in an environmental scanning electron microscope (ESEM) or focused ion beam (FIB) techniques.

Special attention is turned on the micro- and nano-analysis of phases and precipitations and the influence of dopant elements on the structure and behavior of these aluminium-cast-alloys.

For the micro-characterisation the SEM is used in combination with energy dispersive x-ray spectroscopy (EDXS), wavelength x-ray spectroscopy (WDXS) and electron backscatter diffraction (EBSD). Out from regions of interest TEM-lamellas from regions of interest are prepared with the FIB and transfered to the TEM for the nano-characterisation of the samples, using EDXS and electron energy loss spectrometry (EELS/EFTEM) methods and electron diffraction techniques [2]. High resolution scanning transmission electron microscopy analysis on an atomic scale level is focused on the dopant elements (Fig. 3) and is compared with HREM simulations (Fig. 4). This versatile combination of methods leads to a multi-scale-analysis of the investigated materials and helps materials scientists to deepen their know-how.

Ref.:

[1] Zankel, A.; Reingruber, H.; Schröttner, H.: 3D Elemental Mapping in the ESEM - Imaging & microscopy 2 (2011) 35–37

[2] Albu, M.; Li, J.; Kothleitner, G.; Schumacher, P.; Hofer, F.: Atomic resolution STEM analysis of Sr and Yb addition in Al-Si alloys - Mg; Al; Ti Science and Technology (2013) 162 – 162

The authors want to thank the Austrian Research Promotion Agency (FFG) for financial support (PN 839958).

Fig. 1: SEM Backscatter electron image of an AlSi7 alloy.	Fig. 2: 3D reconstruction of the intermetallic phases of an Al-Si-Cu-Mg alloy based on in-situ-ultramicrotomy in an ESEM [1].
Fig. 3: Scanning Transmission Electron Microscopy High Angle Annular Dark Field (STEM-HAADF) image of the eutectic silicium phase with strontium atoms in the interstitial position and EDXS spectra of the marked area [2].	Fig. 4: HAADF simulation of the eutectic silicium phase with strontium atoms in the interstitial position.