The key goals of the World Congress on High Entropy Alloys (HEA 2019) are to convene stakeholders from across areas of modeling and simulation, experimental characterization, and alloy design, to address many fundamental issues in both single-phase and multiphase high entropy alloys (HEAs). This conference will also examine HEA properties and potential engineering applications. Abstracts are encouraged for a range of HEA-related topics, including, but not limited to:
Chain Tsuan Liu City University of Hong Kong, Hong Kong
Presenting: "High Entropy Alloys Based on NiCoFeAlxTiy Hardening with Multicomponent Intermetallic Nanoparticles"
Abstract This paper summarizes our recent work on the study of microstructures and mechanical properties of high-entropy alloys (HEAs) based on NiCoFeAlxTiy. The precipitation of L12-type multi-component nanoparticles strongly enhances the strength of these HEAs at ambient and cryogenic temperatures. The tensile ductility of these HEAs depends on particle sizes, heat treatments, and alloy compositions. A careful control of the precipitation reaction results in a high tensile strength more than 1.5 GPa while still retaining an extraordinary tensile ductility of 50% at room temperature. On the other hand, these precipitation-hardened HEAs exhibit a serious of embrittlement at certain elevated temperatures. Our study reveals that the mid-temperature embrittlement can be alleviated by control of the precipitation reaction on grain boundaries. A brief discussion of the possible development of new high-temperature materials will be also discussed.
About the Speaker
Dierk Raabe Max-Planck-Institut fuer Eisenforschung GmbH, Germany
Presenting: "Metastable High Entropy Alloys"
Abstract The lecture deals with the design of high entropy alloys where metastable phase states are not coincidentally inherited from processing, but rather are engineered. Phase stability can be tuned by chemical composition (thermodynamics, e.g. partitioning), tempering (kinetics, e.g. nucleation), and microstructure (confinement, e.g. size effects). When exposed to loads metastable phases can trigger athermal transformation effects such as TRIP and TWIP. The concept works at the bulk scale and also at a spatially confined microstructure scale, such as at lattice defects. In the latter case, local stability tuning works primarily through segregation engineering, i.e. through targeted elemental partitioning to dislocation cores, stacking faults, interfaces, and precipitates with the aim to render only these confined regions metastable. Depending on stability, spatial confinement, misfit, and dispersion, both bulk and local load-driven athermal transformations can equip high entropy alloys with substantial gain in strength, ductility, and damage tolerance.
Oleg Senkov Air Force Research Laboratory, USA
Presenting: "Refractory Complex Concentrated Alloys for High Temperature Applications: Opportunities and Challenges"
Abstract Refractory complex concentrated alloys (RCCAs), which also include refractory high entropy alloys, are widely studied as candidates for high temperature applications. They are based on three or more refractory elements, have BCC or B2 matrix and may have non-refractory elements and secondary phases. Knowledgeable selection of alloying elements allows production of RCCAs with a wide range of densities and mechanical properties. Simultaneous presence of BCC and B2 phases in some of RCCAs may result in a coherent, superalloy-like nano-phase structure and unique mechanical properties. This new field of research still experiences many challenges, and the effects of the combinations of the alloying elements, thermal and thermo-mechanical processing conditions on the microstructure, mechanical properties and oxidation behavior need to be understood. High-temperature strengthening and deformation mechanisms operating in RCCAs need to be explored. This talk will review current RCCA efforts and will develop ideas to guide future research.
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