β- and δ-Al-Fe-Si intermetallic phase, their intergrowth and polytype formation
Journal article, Peer reviewed
Accepted version
![Thumbnail](/ntnu-xmlui/bitstream/handle/11250/2640503/%25CE%25B2-%2band%2b%25CE%25B4-Al-Fe-Si%2bintermetallic%2bphase%252C%2btheir%2bintergrowth%2band%2bpolytype%2bformation.pdf.jpg?sequence=6&isAllowed=y)
Åpne
Permanent lenke
http://hdl.handle.net/11250/2640503Utgivelsesdato
2019Metadata
Vis full innførselSamlinger
- Institutt for fysikk [2703]
- Institutt for materialteknologi [2552]
- Publikasjoner fra CRIStin - NTNU [38484]
Sammendrag
Crystal structure characteristics of coexisting β and δ phase were investigated in a purely intermetallic Al-Fe-Si alloy and in plate-shaped intermetallic particles formed in a model secondary Al7.1Si1.2Fe0.3Mn alloy. The β- and the δ-Al-Fe-Si intermetallic phase are thermodynamic and crystallographic distinct phases despite some structural similarities. Nevertheless, both phases can appear severely intergrown within single plate-shaped particles after solidification of Fe-containing secondary Al-Si alloys under non-equilibrium conditions which is attributed to the good fit along the (001) planes of both phases. Thereby, few layers of the δ-like stacking sequences within the β phase can be considered as a typical planar defect of the β phase. The β phase exhibits polytype structures for which structural models have been formulated based on ordering of the constituting double layers being shifted by a/2 or b/2 displacements leading to 4 different double layer positions A, B, C, and D. An AB polytype with idealized Acam symmetry actually shows a monoclinic distortion towards A12/a1 symmetry. An ABCD polytype with idealized I41/acd symmetry has been derived, too. Next to the ordered polytypes, stackings with non-periodic sequences of A, B, C and D double layers exist.