title: Orientation relationship of eutectoid FeAl and FeAl2.
abstract: Fe-Al alloys in the aluminium range of 55-65 at.% exhibit a lamellar microstructure of B2-ordered FeAl and triclinic FeAl2, which is caused by a eutectoid decomposition of the high-temperature Fe5Al8phase, the so-called ∊ phase. The orientation relationship of FeAl and FeAl2has previously been studied by Bastinet al.[J. Cryst. Growth(1978 ▸),43, 745] and Hirataet al.[Philos. Mag. Lett.(2008 ▸),88, 491]. Since both results are based on different crystallographic data regarding FeAl2, the data are re-evaluated with respect to a recent re-determination of the FeAl2phase provided by Chumaket al.[Acta Cryst.(2010 ▸), C66, i87]. It is found that both orientation relationships match subsequent to a rotation operation of 180° about a 〈112〉 crystallographic axis of FeAl or by applying the inversion symmetry of the FeAl2crystal structure as suggested by the Chumak data set. Experimental evidence for the validity of the previously determined orientation relationships was found in as-cast fully lamellar material (random texture) as well as directionally solidified material (∼〈110〉FeAl|| solidification direction) by means of orientation imaging microscopy and global texture measurements. In addition, a preferential interface between FeAl and FeAl2was identified by means of trace analyses using cross sectioning with a focused ion beam. On the basis of these habit planes the orientation relationship between the two phases can be described by ([Formula: see text]01)FeAl|| (114)[Formula: see text] and [111]FeAl|| [1[Formula: see text]0][Formula: see text]. There is no evidence for twinning within FeAl lamellae or alternating orientations of FeAl lamellae. Based on the determined orientation and interface data, an atomistic model of the structure relationship of Fe5Al8, FeAl and FeAl2in the vicinity of the eutectoid decomposition is derived. This model is analysed with respect to the strain which has to be accommodated at the interface of FeAl and FeAl2.
authors.affiliation: Institute of Applied Materials (IAM-WK), Karlsruhe Institute of Technology (KIT) , Karlsruhe, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Scherf
authors.affiliation: Institute of Applied Materials (IAM-WK), Karlsruhe Institute of Technology (KIT) , Karlsruhe, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Kauffmann
authors.affiliation: Institute for Technical Physics (ITEP), Karlsruhe Institute of Technology (KIT) , Karlsruhe, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Kauffmann-Weiss
authors.affiliation: Institute of Nanotechnology (INT), Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany; Karlsruhe Nano Micro Facility (KNMF), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, Eggenstein-Leopoldshafen, 76344, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Scherer
authors.affiliation: Structure and Nano-/Micromechanics of Materials, Max-Planck-Institut für Eisenforschung , Düsseldorf, Germany.
authors.forename: X
authors.initials: X
authors.lastname: Li
authors.affiliation: Structure and Nano-/Micromechanics of Materials, Max-Planck-Institut für Eisenforschung , Düsseldorf, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Stein
authors.affiliation: Institute of Applied Materials (IAM-WK), Karlsruhe Institute of Technology (KIT) , Karlsruhe, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Heilmaier
keywords: electron backscatter diffraction; eutectoid decomposition; interfaces; iron aluminides