Identification of Fe-bearing phases in the as-cast microstructure of AA6026 alloy and their evolution during homogenization treatment
J. Min. Metall. Sect. B-Metall., 59 (2) (2023) 327-338. DOI:10.2298/JMMB230611028R
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Available online 06 novembar 2023
(Received 11 June 2023; Accepted 02 November 2023)
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The Fe-bearing intermetallic phases present in the as-cast AA6026 alloy and their evolution during homogenization treatments at 480-550°C were investigated using optical microscopy, SEM, and TEM techniques in combination with EDS analysis. In addition to the α-Al(Fe,Mn)Si phase with dendritic morphology, two types of plate-like Fe-bearing microconstituents were revealed in the microstructure of the as-cast alloy. The EDS microanalysis and electron diffraction showed that one set of platelets represented only thin sections of α-Al(Fe,Mn)Si microconstituent. The other set of plate-like microconstituents was identified as a tetragonal, silicon-rich δ-Al4(Fe,Mn)Si2 phase. The formation of the δ-Al4(Fe,Mn)Si2 phase was attributed to the chemical composition of the alloy. During homogenization, the metastable δ-Al4(Fe,Mn)Si2 transformed into the α-Al(Fe,Mn)Si phase and fragmented. The dendritic α-Al(Fe,Mn)Si microconstituents were also fragmented. However, while the α-Al(Fe,Mn)Si microconstituents preserved a b.c.c. crystal lattice throughout the process, the product of the transformation of the δ-Al4(Fe,Mn)Si2 phase exhibited primitive cubic lattice.
Keywords: 6xxx alloys; Fe-bearing microconstituents; δ-Al4(Fe,Mn)Si2 phase; Homogenization; Phase transformation
Correspondence Address:
T. Radetić,
University of Belgrade, Faculty of Technology and Metallurgy, Belgrade, Serbia;
email: tradetic@tmf.bg.ac.rs
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