Symposium PM04-High-Entropy Alloys

Unlike most conventional alloys that consist of a major principal element, the new class of high-entropy alloys (HEAs) comprise multiple principal elements in high concentrations. The original rationale for the name was that high configurational entropy of mixing was expected to promote formation of solid solutions by suppressing intermetallic compounds. As it turns out, this happens infrequently; multi-phase alloys tend to be more common. Therefore, a broader name for these alloys is compositionally complex alloys (CCAs). Together, HEAs and CCAs occupy a vast unexplored space near the centers of phase diagrams where there are many new materials waiting to be discovered with potentially superior properties. Furthermore, within this space, there are fascinating unanswered questions about how to quantify compositional complexity and its effects on basic structure-property relationships.

This symposium focuses on both fundamental and practical aspects of HEAs and CCAs and their governing structure-property relationships. We solicit papers that address these issues using experimental and/or theoretical approaches. Of special interest are new developments in alloy design targeting properties beyond those possible with conventional alloys, as well as unique aspects of HEAs/CCAs attributable to their chemical and structural complexity.

• Thermodynamics of phase stability, kinetics, diffusion mechanisms.
• Mechanical properties: ductility, strength, fatigue, fracture, and their temperature and strain rate dependences.
• Governing mechanisms: solid solution strengthening, precipitation strengthening, twinning, dislocation structures, work hardening.
• Microstructure control for property optimization, similarities/differences to TWIP/TRIP materials.
• Effects of compositional complexity on physical and mechanical properties.
• Theoretical descriptions and experimental measurements of local and long-range disorder/atomic displacements and their effects on properties.
• Theoretical/experimental approaches to efficiently identify useful compositions in multi-dimensional space.
• Potential/realized applications and the critical/relevant properties that make them possible.

• Hongbin Bei (Oak Ridge National Laboratory, USA)
• Jean-Philippe Couzinie (ICMPE-CNRS, Paris Est, France)
• William Curtin (École Polytechnique Fédérale de Lausanne, Switzerland)
• Guillaume Laplanche (Ruhr University Bochum, Germany)
• Zhaoping Lu (University of Science and Technology Beijing, China)
• Michael Mills (The Ohio State University, USA)
• Jörg Neugebauer (Max Planck Institute for Iron Research, Germany)
• Shigenobu Ogata (Osaka University, Japan)
• Robert Ritchie (Lawrence Berkeley National Laboratory, USA)
• Ming-Hung Tsai (National Chung Hsing University, Taiwan)
• Nobuhiro Tsuji (Kyoto University, Japan)
• Qian Yu (Zhejiang University, China)