Journal of Mining and Metallurgy. Section B: Metallurgy (Jan 2023)

Identification of Fe-bearing phases in the as-cast microstructure of AA6026 alloy and their evolution during homogenization treatment

  • Radetić T.,
  • Popović M.,
  • Novaković M.,
  • Rajić V.,
  • Romhanji E.

DOI
https://doi.org/10.2298/JMMB230611028R
Journal volume & issue
Vol. 59, no. 2
pp. 327 – 338

Abstract

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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 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 underwent fragmentation. 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.

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