title: Influence of W, Mo and Ti trace elements on the phase separation in Al8Co17Cr17Cu8Fe17Ni33 based high entropy alloy.
abstract: Compositionally complex alloys, also called high entropy alloys, have been investigated for over a decade in view of different applications, but so far only a small number of alloys can be considered as presenting good enough properties for industrial application. The most common family of elements is Al-Co-Cr-Cu-Fe-Ni. The equiatomic alloy having 5 phases and being too brittle, the composition has been modified in order to improve the mechanical properties. Different compositions have been tested and as a first result ductile Al8Co17Cr17Cu8Fe17Ni33 has been chosen for deeper investigation. It shows a dendritic segregation into Co-Cr-Fe rich cores and Al-Cu-Ni rich interdendritic sites. The as-cast state is characterized mainly by two phases, namely Al-Cu-Ni rich precipitates of L12 structure inside a solid solution matrix. After homogenization both alloys consists of a single solid solution phase. Results are compared to calculations by ThermoCalc. In order to further improve the properties of the alloy the Cr content has been decreased and replaced by trace elements W, Mo and Ti, which, according to ThermoCalc, increase the melting point and the phase transition temperature which leads to the formation of the L12 phase. As-cast and heat treated samples of the base and the modified alloy have been investigated by transmission electron microscopy and three dimensional atom probe. Results of the investigations will be discussed in terms of microstructure, hardness and coherence with Thermo Calc predictions.
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany. Electronic address: anna.manzoni@helmholtz-berlin.de.
authors.forename: Anna M
authors.initials: AM
authors.lastname: Manzoni
authors.affiliation: Metals and Alloys, University Bayreuth, Lu dwig-Thoma-Str. 36b, 95447 Bayreuth, Germany.
authors.forename: Haneen M
authors.initials: HM
authors.lastname: Daoud
authors.affiliation: Metals and Alloys, University Bayreuth, Lu dwig-Thoma-Str. 36b, 95447 Bayreuth, Germany.
authors.forename: Rainer
authors.initials: R
authors.lastname: Voelkl
authors.affiliation: Metals and Alloys, University Bayreuth, Lu dwig-Thoma-Str. 36b, 95447 Bayreuth, Germany.
authors.forename: Uwe
authors.initials: U
authors.lastname: Glatzel
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany.
authors.forename: Nelia
authors.initials: N
authors.lastname: Wanderka
keywords: Atom probe tomography; Compositionally complex alloys; High entropy alloys; Transmission electron microscopy