Multi-modal characterization of the B2 phase in the Ta-Re binary system

Bryan J. Crossman; Junxin Wang; Loic Perrière; Si Athena Chen; Jean Philippe Couzinié; Maryam Ghazisaeidi; Michael J. Mills

doi:10.1016/j.actamat.2025.121097

Multi-modal characterization of the B2 phase in the Ta-Re binary system

Bryan J. Crossman
, Junxin Wang
, Loic Perrière
, Si Athena Chen
, Jean Philippe Couzinié
, Maryam Ghazisaeidi
, Michael J. Mills

Powder Diffraction

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3 Scopus citations

Abstract

The energy and transportation industries demand materials that retain their mechanical property at high temperatures. Refractory complex concentrated alloys (RCCAs) with a BCC + B2 microstructure offer a potential solution, where maintaining the high temperature mechanical properties can be achieved by precipitation strengthening. This depends on the B2 phase in RCCAs being thermodynamically stable with a high solvus temperature. Recently, we predicted the high temperature stability of the B2 structure in the Ta-Re binary system, using density functional theory. Here, we provide experimental evidence for the existence of this phase for the first time, using a Ta₆₅Re₃₅ alloy. Despite Ta-Re binary phase diagrams predicting a single-phase BCC microstructure for Ta₆₅Re₃₅, we show that a high Z nanoscale secondary phase appears after heat treatment at 1550 °Cand 1100 °C. Scanning transmission electron microscopy (STEM) revealed that this phase has a cubic structure and is equiatomic TaRe though B2 superlattice reflections were absent in fast Fourier transforms (FFT) and diffraction patterns (DPs). DP simulations indicate that the B2 TaRe superlattice reflections are up to two orders of magnitude weaker than their fundamental reflections, making their detection challenging via electron microscopy. Neutron diffraction confirmed the second phase had a B2 structure. This study identified a previously unobserved high temperature stable B2 phase in the Ta-Re system, enabling the development of new high temperature BCC + B2 RCCAs.

Original language	English
Article number	121097
Journal	Acta Materialia
Volume	293
DOIs	https://doi.org/10.1016/j.actamat.2025.121097
State	Published - Jul 1 2025

Funding

This work is supported by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, grant DE-SC0022043. A portion of this research used resources at the High Flux Isotope Reactor, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory with the aid of Dr. Clarina Dela Cruz. The beam time was allocated to HB-2C WAND² on proposal number IPTS-33577. All the electron microscopy was performed at the Center for Electron Microscopy and Analysis (CEMAS) at The Ohio State University. The authors would like to thank Eric Leroy (ICMPE) for the EPMA analysis of the Ta-Re alloy. A special thanks to Robert Williams (CEMAS) for his insightful discussions related to STEM characterization, specimen preparation, and 4D STEM. Computational resources are provided by the Ohio Supercomputer Center.

Keywords

Electron microscopy
Neutron diffraction
Phase stability
Refractory complex concentrated alloys (RCCAs), Intermetallic phases

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10.1016/j.actamat.2025.121097

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title = "Multi-modal characterization of the B2 phase in the Ta-Re binary system",

abstract = "The energy and transportation industries demand materials that retain their mechanical property at high temperatures. Refractory complex concentrated alloys (RCCAs) with a BCC + B2 microstructure offer a potential solution, where maintaining the high temperature mechanical properties can be achieved by precipitation strengthening. This depends on the B2 phase in RCCAs being thermodynamically stable with a high solvus temperature. Recently, we predicted the high temperature stability of the B2 structure in the Ta-Re binary system, using density functional theory. Here, we provide experimental evidence for the existence of this phase for the first time, using a Ta65Re35 alloy. Despite Ta-Re binary phase diagrams predicting a single-phase BCC microstructure for Ta65Re35, we show that a high Z nanoscale secondary phase appears after heat treatment at 1550 °Cand 1100 °C. Scanning transmission electron microscopy (STEM) revealed that this phase has a cubic structure and is equiatomic TaRe though B2 superlattice reflections were absent in fast Fourier transforms (FFT) and diffraction patterns (DPs). DP simulations indicate that the B2 TaRe superlattice reflections are up to two orders of magnitude weaker than their fundamental reflections, making their detection challenging via electron microscopy. Neutron diffraction confirmed the second phase had a B2 structure. This study identified a previously unobserved high temperature stable B2 phase in the Ta-Re system, enabling the development of new high temperature BCC + B2 RCCAs.",

keywords = "Electron microscopy, Neutron diffraction, Phase stability, Refractory complex concentrated alloys (RCCAs), Intermetallic phases",

author = "Crossman, \{Bryan J.\} and Junxin Wang and Loic Perri{\`e}re and Chen, \{Si Athena\} and Couzini{\'e}, \{Jean Philippe\} and Maryam Ghazisaeidi and Mills, \{Michael J.\}",

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AU - Crossman, Bryan J.

AU - Wang, Junxin

AU - Perrière, Loic

AU - Chen, Si Athena

AU - Couzinié, Jean Philippe

AU - Ghazisaeidi, Maryam

AU - Mills, Michael J.

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N2 - The energy and transportation industries demand materials that retain their mechanical property at high temperatures. Refractory complex concentrated alloys (RCCAs) with a BCC + B2 microstructure offer a potential solution, where maintaining the high temperature mechanical properties can be achieved by precipitation strengthening. This depends on the B2 phase in RCCAs being thermodynamically stable with a high solvus temperature. Recently, we predicted the high temperature stability of the B2 structure in the Ta-Re binary system, using density functional theory. Here, we provide experimental evidence for the existence of this phase for the first time, using a Ta65Re35 alloy. Despite Ta-Re binary phase diagrams predicting a single-phase BCC microstructure for Ta65Re35, we show that a high Z nanoscale secondary phase appears after heat treatment at 1550 °Cand 1100 °C. Scanning transmission electron microscopy (STEM) revealed that this phase has a cubic structure and is equiatomic TaRe though B2 superlattice reflections were absent in fast Fourier transforms (FFT) and diffraction patterns (DPs). DP simulations indicate that the B2 TaRe superlattice reflections are up to two orders of magnitude weaker than their fundamental reflections, making their detection challenging via electron microscopy. Neutron diffraction confirmed the second phase had a B2 structure. This study identified a previously unobserved high temperature stable B2 phase in the Ta-Re system, enabling the development of new high temperature BCC + B2 RCCAs.

AB - The energy and transportation industries demand materials that retain their mechanical property at high temperatures. Refractory complex concentrated alloys (RCCAs) with a BCC + B2 microstructure offer a potential solution, where maintaining the high temperature mechanical properties can be achieved by precipitation strengthening. This depends on the B2 phase in RCCAs being thermodynamically stable with a high solvus temperature. Recently, we predicted the high temperature stability of the B2 structure in the Ta-Re binary system, using density functional theory. Here, we provide experimental evidence for the existence of this phase for the first time, using a Ta65Re35 alloy. Despite Ta-Re binary phase diagrams predicting a single-phase BCC microstructure for Ta65Re35, we show that a high Z nanoscale secondary phase appears after heat treatment at 1550 °Cand 1100 °C. Scanning transmission electron microscopy (STEM) revealed that this phase has a cubic structure and is equiatomic TaRe though B2 superlattice reflections were absent in fast Fourier transforms (FFT) and diffraction patterns (DPs). DP simulations indicate that the B2 TaRe superlattice reflections are up to two orders of magnitude weaker than their fundamental reflections, making their detection challenging via electron microscopy. Neutron diffraction confirmed the second phase had a B2 structure. This study identified a previously unobserved high temperature stable B2 phase in the Ta-Re system, enabling the development of new high temperature BCC + B2 RCCAs.

KW - Electron microscopy

KW - Neutron diffraction

KW - Phase stability

KW - Refractory complex concentrated alloys (RCCAs), Intermetallic phases

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Multi-modal characterization of the B2 phase in the Ta-Re binary system

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