engleski

Investigation of AlSi9MgMn Alloy Solidification by Thermal Analysis

Since aluminium alloys have found their wide application in numerous industries, quality requirements allocated new features regarding microstructural, mechanical and technological properties. Novel multicomponent AlSi9MgMn alloy intended for high pressure die casting has been investigated due to unusual chemical composition. Since this alloy has not been classified in international norm, only briefly described in manufacturer norm, it represents challenge for understanding of its solidification mechanism. Main characteristics of an alloy are related to high manganese and low iron content, and in spite of this, high mechanical properties, first of all, ductility. The aim of this article was to establish solidification sequence of AlSi9MgMn alloy with high Mn addition by numerical calculation of equilibrium phase diagram and differential scanning calorimetry and reconnection of thermodynamic parameters with obtained microstructure. Thermodynamic calculation revealed solidification sequence with corresponded temperatures as follows: precipitation of high temperature AlxMnyFezSiu phase, development of primary dendrite network, main eutectic reaction and finally, in solid state, secondary eutectic phase Mg2Si. Differential scanning calorimetry enables exact temperatures of phase transformations determination. Thermodynamic investigation does not indicate any reaction in solid state. Microstructure investigation by optical and electron microscopy indicates presence of particular phases: primary aluminium dendrites (Al), high temperature Al15(MnFe)3Si2 and Al5FeSi phases, main eutectic Al+Si, intermetallic iron-magnesium phase Al8Mg3FeSi6 developed from needle-like Al5FeSi phases and secondary eutectic phase on the magnesium base in a form of binary eutectic (Al + Mg2Si). Synergy of performed thermodynamic and microstructural investigation enables exact solidification sequence establishment with reaction and corresponding temperatures.

AlSi_9MgMn alloy ; solidification sequence ; thermal anlalysis ; microstructure

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