Effects of B addition on microstructure and thermal conductivity of Cu–B composites produced by hot-extrusion of elemental powders

ABSTRACT

This work proposes a new neutron absorber, Cu–B composites, with excellent thermal conductivity and good neutron absorbing capability. Mixtures of elemental Cu and B powders with the B contents varying between 10 and 40 at.-% were consolidated into round bars by hot extrusion. The addition of B significantly refined the grain structure, which is related to the suppression of dynamic recrystallisation during hot extrusion and extended recovery during subsequent annealing. Such fine-grained structure in Cu–B composites together with dispersion hardening by B particles contributed to the higher hardness of Cu–B composites. The thermal conductivity of Cu–B composites, being roughly two times higher than that of Al–B₄C MMC, decreases with increasing the B contents, which is mainly due to higher volume fraction B particles with lower thermal conductivity, and partly to texture randomisation and refined grain structure in the Cu–B composites.

KEYWORDS:

• Neutron absorber
• spent nuclear fuel
• thermal conductivity
• powder metallurgy
• hot extrusion
• texture

Acknowledgements

The authors wish to thank Mr. Jihoon Kang for sample preparation for metallography and to Dr. Daejong Kim for the measurement of thermal properties. The authors also thank Daehan Industry for hot extrusion of Cu–B composites.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was financially supported by the Korea Atomic Energy Research Institute R&D program with a contract number of 524480-23 and partially by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) (NRF Project No.: 2022M3H4A3046292).

Notes on contributors

Young-Bum Chun

Young-Bum Chun is a principal researcher at Korea Atomic Energy Research Institute.

SeungHyeok Chung

Seung Hyeok Chung is a professor and Ph.D student, respectively, at Korea Advanced Institute of Science and Technology.

Chang-Kyu Rhee

Chang-Kyu Rhee is a principal researcher at Korea Atomic Energy Research Institute.

Ho Jin Ryu

Ho Jin Ryu is a professor and Ph.D student at Korea Advanced Institute of Science and Technology.