Structure and thermodynamic properties of a high-entropy TiZrNbHfTa alloy

• Applicant: Dr.-Ing. Junhee Han
• Subject Area: Thermodynamics and Kinetics as well as Properties of Phases and Microstructure of Materials ; Mechanical Properties of Metallic Materials and their Microstructural Origins
• Term: from 2016 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 298786643

The proposed research aims at contributing to a fundamental understanding of structure-property relationship of the so-called high-entropy alloys (HEAs). HEAs are a new type of metallic materials and originally defined as homogeneous solid solution alloys composed of more than five constituent elements in equal or near equal atomic proportions with simple crystal structures such as fcc and bcc instead of formation of multiple intermetallic phases. In the refractory HEAs formation of the disordered single-phase bcc microstructure with comparable high-temperature mechanical properties to conventional superalloys was reported.In this project, one particular refractory HEA, the equiatomic TiZrNbHfTa alloy and its corresponding subsystems will be investigated in terms of structure formation and thermodynamic properties aiming to aid the design of alloys for optimal properties. This alloy system was chosen because its structure formation and thermodynamic stability are yet unknown in detail despite the fact that its high-temperature mechanical performance is relatively well determined. Thus, for such high-temperature materials, the understanding of structure formation and thermodynamic stability would be not only of great scientific interest but also of practical importance especially for thermal cycling in high-temperature applications.The main objectives of this project are: 1) to determine the thermodynamic properties and thermal stability of the bcc phase of the equiatomic TiZrNbHfTa alloy, as well as the corresponding subsystems under equilibrium and non-equilibrium conditions. 2) To derive a quantitative determination of the structure formation especially with respect to the lattice distortion in both bulk and atomic scale and the local atomic structure in the bcc crystal lattice of the high-entropy TiZrNbHfTa alloy. Based on the findings in this project, a deeper understanding of the structure-properties relationship for HEAs is expected.

• DFG Programme: Research Grants
• International Connection: Austria, South Korea, USA
• Cooperation Partners: Dr. Jozef Bednarcik; Professor Dr.-Ing. Jürgen Eckert; Professor Do-Hyang Kim, Ph.D.; Dr.-Ing. Yue Zhang