1.
R. Doepp*
*Institute for Metallurgy, Technical University Clausthal, Germany
CONTRIBUTION TO STRUCTURE AND PROPERTIES OF MALLEABLE CAST IRON

2.
J.H. Li1 and P. Schumacher1,2
1 Montanuniversität Leoben, Leoben, Austria
2 Austrian Foundry Research Institute, Leoben, Austria
REVEALING THE MODIFICATION OF EUTECTIC SI IN AL ALLOY BY ADVANCED ELECTRON MICROSCOPY

3.
Franc Zupanič, Gorazd Lojen, Tonica Bončnina
University of Maribor, Faculty of Mechanical Engineering, Slovenia
APPLICATION OF A FOCUSSED ION BEAM BY CHARACTERIZATION OF CASTING AL-ALLOYS

4.
Jianmin Shi, Helge Pries, Elisabeth Stammen Klaus Dilger
Institute of Joining and Welding, Technische Universität Braunschweig, Germany
CORROSION AND DURABILITY OF ADHESIVELY BONDED HIGH-PRESSURE DIE CAST ALUMINUM ALLOYS

1.
R. Doepp*
*Institute for Metallurgy, Technical University Clausthal, Germany
CONTRIBUTION TO STRUCTURE AND PROPERTIES OF MALLEABLE CAST IRON

Abstract

Regarding chemical composition, solidification behaviour, structure and properties malleable cast iron has proofed in past and present time and has good chances in future, too, compare [29]. The assistance of teachers, colleagues and co-workers in Aachen, Ennepetal and Clausthal is gratefully acknowledged.

This contribution is dedicated worldwide to all foundrymen, who are engaged with malleable cast iron in practice, research, development and teaching. Two representative colleagues were Mr. Hans J. Heine, Technical Director of the Malleable Founders Society, Cleveland, Ohio, USA, and Prof. Dr.-Ing. Milan Trbizan, Technical University of Ljubljana and Drustvo Livarjev Slovenije.

Furthermore, this contribution is dedicated to our family company Friedr. Ischebeck GmbH in Ennepetal, Germany, founded 1881 by our great-grandfather Friedrich Ischebeck as forge for vices, with a malleable cast iron foundry since 1912, later additional gray cast iron. These 105 years of experience in malleable cast iron procedure are a bridge into future.

Abstract

Modifying the eutectic Si from flake-like to fibrous is a key factor to improve the properties of Al-Si alloys. The impurity-induced twinning (IIT) mechanism and the twin plane re-entrant edge (TPRE) mechanism as well as the poisoning of the TPRE mechanism are generally accepted to be valid under certain conditions. However, IIT, TPRE or poisoning of TPRE mechanism cannot be used to interpret all the observations accompanying modification, indicating that other factors may be also valid. In this paper, we overview the progress of modification of eutectic Si, which in particular focus on the application of advanced electron microscopy. It is very clear that advanced electron microscopy, including high angle annular dark field imaging (HAADF) and electron energy loss spectroscopy (EELS) in scanning transmission electron microscopy (STEM) as well as atom probe tomography 76 Livarski vestnik, letnik 65, št. 2/2018 (APT), can provide a great tool to elucidate the modification mechanism of eutectic Si. Apart from the application of advanced electron microscopy, atomic simulation based on density functional theory (DFT) calculation was also found to be very efficient to elucidate the bonding behaviour of modifying elements within Si twins and its effect on the Si twinning. From both experimental and simulation investigation, it was found that modifying elements have four different roles: (i) the adsorption at the intersection of Si facets, inducing IIT growth mechanism, (ii) the adsorption at the twin plane re-entrant edge, inducing TPRE growth mechanism, (iii) the adsorption ahead of the growing Si twins, inducing a solute entrainment within eutectic Si, and (iv) the segregation at the interface between eutectic Si and eutectic Al, suppressing the growth of eutectic Si. The importance of advanced electron microscopy (HAADF-STEM, EELS and APT) in the field of solidification is also highlighted.

Keywords: Al-Si alloy; Nucleation; Growth; Eutectic solidification; Advanced electron microscopy; Density functional theory calculation.

3.
Franc Zupanič, Gorazd Lojen, Tonica Bončnina
University of Maribor, Faculty of Mechanical Engineering, Slovenia
APPLICATION OF A FOCUSSED ION BEAM BY CHARACTERIZATION OF CASTING AL-ALLOYS

Abstract

Microstructures of cast aluminium alloys consist of numerous micro- and nanosized microstructural constituents. For metallographic investigations, several standard methods have been used: light microscopy (LM), scanning (SEM) and transmission (TEM) electron microscopies combined with several analytical techniques, and X-ray diffraction (XRD). Additional information regarding the microstructure can be obtained by a dual beam microscopy: focussed ion beam (FIB) and electron beam (SEM). The focussed ion beam is a device, in which a gallium ion beam is produced with a diameter ranging from few nanometres up to few micrometres. Collisions of ions with a sample result in scattering of atoms and ions from its surface, causing formation of different signals. By the application of a dual beam, the FIB modifies the surface, while SEM is used for the imaging. In this article, we present the use of the dual beam (FIB-SEM) for metallography of selected aluminium casting alloys. The advantage of this method is a possibility to create cross-sections at particular sites and reveal the shapes and distributions of microstructural constituents, which are below the surface of a sample. We briefly represent the procedure for making serial cuts and spatial (3D) reconstruction of microstructure.

Keywords: aluminium alloy, casting, focussed ion beam, characterization, microstructure

Abstract

High-pressure die casting of Al alloys is an attractive manufacturing process for the production of aluminum components used in the automobile, construction and aerospace industry. Joining of high-pressure die cast aluminum components with other structural parts using adhesives is still challenging, due to the inherent contamination of casting surfaces by die lubricants and the inhomogeneous distribution of alloying elements on the surface. In this lecture we will report on the development of a universal chemical pretreatment process for the reliable fabrication of adhesively bonded HPDC aluminum alloys. The effectiveness of chemical pre-treatment processes was evaluated by comparison of surface morphologies and chemical compositions, corrosion parameters before and after chemical treatment, as well as adhesion properties without and with aging. The validation of the developed chemical pre-treatment process including degreasing in NaOH solutions, de-oxidation in fluoride-containing sulfuric acid solutions and dipping in hexaflurotitanic acid solutions, on high-pressure die cast components from the industry will be demonstrated.

Keywords: high-pressure die casting, aluminum alloys, surface characterization, corrosion, adhesive bonding, durability