Secondary Al-Si-Mg High-pressure Die Casting Alloys with Enhanced Ductility
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THE majority of common high-pressure die casting (HPDC) alloys used in the transport industry are based on the aluminum-silicon-magnesium system due to its excellent casting abilities.[1–3] As high ductility is absolutely mandatory for the implementation of aluminum in structural casting components, the alloy systems used today are produced from primary aluminum to keep impurities as low as possible and ensure good deformability. Several primary aluminum alloys have been developed for that purpose (e.g., Table I). All the listed ductile alloys share the fact that their iron content is strictly limited to avoid the formation of undesired intermetallic phases, especially of the plateshaped b-Al5FeSi phase, whose detrimental effect on the DOMINIK BO¨SCH, formerly with the Department of Materials Science and Engineering, Institute 1: General Materials Properties, University Erlangen–Nu¨rnberg, 91058 Erlangen, Germany, is now Development Engineer, with the AUDI AG, 85045 Ingolstadt, Germany. STEFAN POGATSCHER, Postdoc, is with the Laboratory of Metal Physics and Technology, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland. MARC HUMMEL, Development Engineer, is with the AUDI AG, 74148 Neckarsulm, Germany. WERNER FRAGNER, Head of Corporate Technology, is with the Austria Metall AG (AMAG), 5282 Ranshofen, Austria. PETER J. UGGOWITZER, Professor, is with the Laboratory of Metal Physics and Technology, Department of Materials, ETH Zurich. MATHIAS GO¨KEN, Professor, and HEINZ WERNER HO¨PPEL, Senior Scientist, are with the Department of Materials Science and Engineering, Institute 1: General Materials Properties, University Erlangen– Nu¨rnberg. Contact e-mail: [email protected]. Manuscript submitted September 16, 2014. Article published online December 10, 2014 METALLURGICAL AND MATERIALS TRANSACTIONS A
mechanical properties of Al-Si alloys is well known and has been described extensively.[1–8] In contrast, usual secondary HPDC alloys possess iron contents of 1 to 2 wt pct, making them easy recyclable from different alloy families, but at the expense of an extremely poor deformability. While secondary aluminum alloys are beneficial for practical, economical, and ‘carbon-footprint’ points of view, their increased iron content is still the key obstacle to a widespread use in casting applications which require high ductility. Accordingly, various means and methods to prevent b-phase formation have been discussed in the literature.[1–6] This prevention can be achieved either by influencing the solidification process[3,7,8] or by adding so called ‘iron correctors’ such as Mn, Cr, and Co, which replace the b-phase by the favored polyhedral-shaped a-Al15(Fe,Mn)3Si2-phase.[1–6] For large-scale industrial usage, the Fe correction with Mn is accepted as the preferred economical solution due to its easy and uncritical implementation, and its relatively low price compared to other potential corrector elements. In addition, manganese helps to prevent die soldering during processing. When typical secondary alloys with iron
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