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Fundamental Study of Strong and Ductile Single BCC Phase Refractory High-entropy Alloys for High-temperature Applications

Author: Date:2020-06-26 Source:

Speaker: Dr. Chanho Lee

Affiliation: Los Alamos National Laboratory, U.S.

Contact: Prof. Yong Zhang

Date: July 03rd (Friday), 2020

ZOOM Cloud Meeting ID: 5610133397

Abstract: Severe distortion is one of the four core effects in single phase high entropy alloys (HEAs) and contributes significantly to the yield strength. However, the connection between the atomic scale lattice distortion and macro scale mechanical properties through experimental verifications has yet to be fully achieved, owing to two critical challenges: (1) the difficulty in the development of homogeneous single phase solid solution HEAs and (2) the ambiguity in describing the lattice distortion and related measurements and calculations. We have developed the single phase body centered cubic (BCC) refractory HEA, NbTaTiVZr, using thermodynamic modeling coupled with experimental verifications. Compared to our previously developed single phase NbTaTiV HEA, the NbTaTiVZr HEA shows a higher yield strength. The increase in yield strength is systematically and quantitatively studied in terms of lattice distortion using a theoretical model, first principles calculations, synchrotron X ray/neutron diffraction, and scanning transmission electron microscopy techniques. These results demonstrate that severe lattice distortion is a core factor for developing high strengths in refractory HEAs.

Speaker’s short biography: Dr. Chanho Lee now is working as a Post Doc with Materials Science in Radiation & Dynamic Extremes in Center for Integrated Nanotechnologies, Los Alamos National Laboratory. He obtained his Dr. degree in University of Tennessee, Knoxville. He participated in several scientific research projects on high entropy alloys. His Dissertation Title for PhD. was Design and Development of Strong and Ductile Single BCC Refractory High entropy Alloys for High temperature Applications. He has obtained Chancellor’s Citation Award Extraordinary Professional Promise, The University of Tennessee, Knoxville for three times, and other awards like best student poster award and excellent paper award . He has published more than ten SCI publications in Acta Materialia, J. Alloys and Comps., Metallurgy and Materials Transaction A etc. of which the highest citations is 63 times per article. He participated in the international conferences such as TMS and gave oral presentations more than ten times. He is a reviewer for Acta Materialia, Scripta Materialia, Journal of Materials Research, and Scientific Reports.