SPP 2006:  Compositionally Complex Alloys - High Entropy Alloys (CCA - HEA)

• Subject Area: Materials Science and Engineering ; Chemistry ; Mechanical and Industrial Engineering ; Physics
• Term: since 2017
• Website: Homepage
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 313773923

Recently, a novel class of metallic alloys, referred to as “high entropy alloys” (HEA) or "compositionally complex alloys" (CCA), has been introduced. These alloys consist of near-equiatomic concentrations of multiple metallic elements. As such, they fundamentally differ from conventional alloys, which commonly consist of a primary element with additions of secondary (alloying) elements in order to achieve desired properties. This new concept of alloy design with no base element opens up a huge multi-component space with significant technological potential and poses challenging scientific questions.The aim of this Priority Programme is to develop CCA and HEA with outstanding mechanical properties or displaying unusual phenomena, which cannot be obtained in conventional alloys, or be explained by current textbook-level theory. Within this programme, alloys with five or more elements are targeted, each having a concentration between 5 and 35 at. %. Lower-order subsets of these alloys, namely binaries, ternaries and quaternaries, may be investigated in supporting roles only, in order to gain basic understanding of CCA and HEA. In order to optimise targeted materials properties, small additions of minor alloying elements such as C, B, Hf, Zr, Si, etc., are permitted.The Priority Programme will comprise two branches:High entropy alloys, HEA, which are defined within this Priority Programme as single solid solution phases, preferably with simple crystal structures.Compositionally complex alloys, CCA, consisting of multiphase microstructures with two or more phases, which may include a solid solution phase.The HEA branch aims at the achievement of a basic-scientific understanding of materials properties that are due to the high entropy effect:Identification of specific properties that occur as a consequence of the salient features of HEA.Repudiation of interpretations mistakenly ascribing properties as being specific to HEA.Fundamental understanding of the characteristic structural and microstructural features of HEA, with particular attention to their influence on mechanical properties.The CCA branch will follow a more application-oriented approach. The aim is to identify and to tailor chemical, crystallographic or microstructural features that govern promising mechanical properties of CCA, making them attractive for future application. Alloys considered should have additional characteristics such as:Adequate room-temperature properties (including tensile ductility and fracture toughness).Ability to be produced in sufficiently large quantities (> 100 g and > 100 mm in size), which allow for conclusive determination of materials properties.Machinability, so that desired specimen geometries can be prepared.In the CCA branch, special emphasis shall be placed on thorough characterisation of mechanical properties of the alloys, resulting in the need to include tensile testing. However, in order to support the application-oriented approach,

• DFG Programme: Priority Programmes
• International Connection: India, Slovakia, USA

Projects

• Coordination Funds (Applicant Glatzel, Uwe )
• Deformation Mechanisms in FCC and BCC High Entropy Alloys Under Various Conditions (Applicants Kauffmann, Alexander ;  Weiss, Klaus-Peter )
• Design and mechanical properties of compositionally complex alloys from twinning-induced towards bidirectional transformation-induced plasticity (MULTI-TRIP CCAs) (Applicants Körmann, Fritz ;  Raabe, Dierk )
• Development of refractory metal-based CCAs with improved mechanical properties (Applicants Christ, Hans Jürgen ;  Heilmaier, Martin )
• High-throughput experimental and Calphad screening of CCAs (Hi-TeCC) - towards new alloys with exceptional mechanical properties (Applicants Haase, Christian ;  Hallstedt, Bengt )
• Identification of the intrinsic deformation mechanisms of single phase body-centered cubic high entropy alloys (Applicants Gruber, Patric Alfons ;  Schwaiger, Ruth )
• Local-to-average crystal structures and mechanical properties in High-Entropy and Compositionally Complex fcc, bcc and hcp-based alloys studied by synchrotron methods (Applicant Fantin, Ph.D., Andrea )
• Materials Development and Mechanical Properties of Single-Phase High Entropy Alloys (Applicants Feuerbacher, Michael ;  Glatzel, Uwe )
• Mechanical properties and hydrogen tolerance of particle-reinforced CCA produced by additive manufacturing (MarioCCArt) (Applicants Dehm, Gerhard ;  Ellendt, Nils ;  Jägle, Eric A. )
• New Quinary and Senary High Entropy Shape Memory Alloys (HE-SMA) – Exploring and Exploiting Martensitic Transformations and Shape Memory Effects in Chemically Complex Systems (Applicants Eggeler, Gunther ;  Frenzel, Jan ;  Maier, Hans Jürgen )
• Phase stability, precipitation kinetics, nanoscale elemental distributions and their effect on tensile properties in refractory TiZrNbHfTa BCC high-entropy alloys (Applicants Laplanche, Ph.D., Guillaume ;  Li, Ph.D., Tong )
• Polycrystalline High Entropy Superalloys (PHESA) – Combining novel strengthening mechanisms in compositionally complex CoNiCr-based superalloys with a large fraction of multicomponent intermetallic precipitates (Applicant Neumeier, Steffen )
• Strength and deformation of precious high entropy alloys (Applicant Freudenberger, Jens )
• Tailored precipitation (B2, L21) strengthened, compositionally complex FeAlCr (Mn, Co, Ni, Ti) alloys for high temperature applications (Applicants Liebscher, Christian ;  Schneider, Ph.D., Jochen M. )
• Thermomechanical properties and microstructure of fcc and bcc high-entropy alloys (Applicants Albe, Karsten ;  Durst, Karsten ;  Wilde, Gerhard )

• Spokesperson: Professor Dr.-Ing. Uwe Glatzel