Microstructure stability and self-diffusion in the equiatomic HfScTiZr HCP multi-principal element alloy

Journal of Alloys and Compounds, vol. 976, pp. 173196

Abstract

Tracer diffusion of 44Ti, 46Sc and 89Zr in the hexagonal close-packed (HCP) HfScTiZr multicomponent alloy is investigated using the radiotracer technique. The microstructure stability is thoroughly examined by conducting prolonged heat treatments between 873 K and 1373 K to mimic the diffusion conditions. Electron microscopy analysis reveals that the alloy contains a mixture of two HCP phases with similar lattice constants, among which the major phase is enriched in Sc, whereas the minor phase is strongly enriched in Ti. The thermal stability is assessed by ab initio-informed calculations which support the existence of the two HCP phases. The Sc diffusion coefficients differ markedly between the HCP phases, while only marginal influence is found for the diffusion of Zr and Ti. The Arrhenius parameters are determined, i.e., the activation energy and the pre-factor. The diffusion properties are analyzed in correlation with the microstructure stability and the ab initio-informed thermodynamic results. The DFT-calculated mean squared atomic displacements, which represent the lattice distortions, are found to provide an appropriate parameter for predicting the diffusion trends of the individual elements. The phase analysis is further compared with existing CALPHAD-type predictions, and the discrepancies between the theoretical assessments and experimental observations are examined and discussed.

Authors 11

1. Garlapati Mohan Muralikrishna corresponding

   University of Münster

   Affiliation as printed

   Institute of Materials Physics, University of Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany

2. Sandipan Sen

   University of Münster

   Affiliation as printed

   Institute of Materials Physics, University of Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany

3. Sai Kumaran Ayyappan

   Indian Institute of Technology Madras

   Affiliation as printed

   Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Madras 600036, Chennai, India

4. Krishnamoorthy Guruvidyathri

   University of Hyderabad

   Affiliation as printed

   School of Engineering Sciences and Technology, University of Hyderabad, Prof CR Rao Road, Gachibowli, Hyderabad 500046, India

5. Juliana Schell

   University of Duisburg-Essen · European Organization for Nuclear Research

   Affiliation as printed

   European Organization for Nuclear Research (CERN), CH-1211 Geneva, Switzerland

   Institute for Materials Science and Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen, Essen, Germany

6. Łukasz Rogal

   Institute of Metallurgy and Materials Science · Polish Academy of Sciences

   Affiliation as printed

   Institute of Metallurgy and Materials Science, Polish Academy of Sciences, Reymonta 25 St., 30-059, Krakow, Poland

7. Xi Zhang

   University of Stuttgart

   Affiliation as printed

   Institute for Materials Science, University of Stuttgart, Pfaffenwaldring 55, Stuttgart 70569, Germany

8. Joachim Mayer Aachen Central Facility for Electron Microscopy

   Forschungszentrum Jülich · Ernst Ruska Centre · RWTH Aachen University

   Affiliation as printed

   Central Facility for Electron Microscopy, RWTH Aachen University, 52074 Aachen, Germany

   Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Forschungszentrum Jülich, 52425 Jülich, Germany

9. Blazej Grabowski

   University of Stuttgart

   Affiliation as printed

   Institute for Materials Science, University of Stuttgart, Pfaffenwaldring 55, Stuttgart 70569, Germany

10. Gerhard Wilde

    University of Münster

    Affiliation as printed

    Institute of Materials Physics, University of Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany

11. Sergiy V. Divinski corresponding

    University of Münster

    Affiliation as printed

    Institute of Materials Physics, University of Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany