Effect of Different Production Methods on the Mechanical and Microstructural Properties of Hypereutectic Al-Si Alloys
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THE hypereutectic Al-Si alloys containing transition metals (TM) are among the structural materials used for high-temperature applications. Compositional modifications of hypereutectic Al-Si alloys made by adding Fe, Co, Cu, and Ni improve mechanical properties at both room and elevated temperatures.[1–3] What makes TMcontaining Al-Si alloys durable at elevated temperatures are TM-containing intermetallic compounds dispersed in the microstructure.[4] Of the transition metals, Fe is probably the most important element for Al-Si alloys, because it cannot be economically removed from molten aluminum.[2] However, in traditional cast Al-Si-Fe alloys, Fe-bearing intermetallic compounds have a tendency to display coarse and needle-like morphologies, which is harmful for mechanical properties because of the stress concentration produced at the tip of the acicular phase during the deformation process. Moreover, there is a big difference in deformation performance between Fe-bearing phase and the Al matrix,
M. FATIH KILICASLAN, Assistant Professor, is with the Department of Materials Science and Nanotechnology Engineering, Kastamonu University, Kastamonu, Turkey. Contact e-mails: [email protected]; [email protected] ORHAN UZUN, Professor, is with the Department of Metallurgical and Materials Engineering, Faculty of Engineering, Bu¨lent Ecevit University, Zonguldak 67100, Turkey. FIKRET YILMAZ, Research Assistant, is with the Department of Physics, Faculty of Art and Science, Gaziosmanpasa University, Tokat, Turkey. SEYIT C¸AG˘LAR, Research Assistant, is with the Department of Metallurgical and Materials Engineering, Faculty of Engineering, Bu¨lent Ecevit University, Zonguldak 67100, Turkey. Manuscript submitted July 12, 2013. METALLURGICAL AND MATERIALS TRANSACTIONS B
which also has a detrimental effect on the mechanical properties.[5,6] In the cast Al-Si-Fe alloys, another subject that should be taken into account is the coarse primary and eutectic silicon phases that deteriorate mechanical properties as well. In fact, in all kinds of AlSi alloys, the size and morphology of primary and eutectic silicon phases have vital importance in terms of mechanical properties. While higher volume fraction of silicon enhances the tensile strength of the alloy, large silicon particles in aluminum matrix can deteriorate the ductility of the alloy. Accordingly, modification of primary and eutectic Si, and neutralization of detrimental effects of Fe-bearing intermetallics in hypereutectic Al-Si-Fe alloys have been studied extensively to ensure reasonable mechanical or tribological properties.[7–10] Modification of silicon particles and Fe-bearing phases can be achieved by different fabrication techniques such as spray deposition, gas atomization, and melt spinning.[11–15] For example, by using spray deposition method, DISPAL series hypereutectic Al-Si-Fe alloys, which are already commercially used, can be successfully produced.[16] Among different fabrication methods, melt spinning and high-energy ball milling are two effec
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