Grain refinement in titanium prevents low temperature oxygen embrittlement

Yan Chong; Reza Gholizadeh; Tomohito Tsuru; Ruopeng Zhang; Koji Inoue; Wenqiang Gao; Andy Godfrey; Masatoshi Mitsuhara; J W Morris Jr; Andrew M Minor; Nobuhiro Tsuji

doi:10.1038/s41467-023-36030-0

Grain refinement in titanium prevents low temperature oxygen embrittlement

Nat Commun. 2023 Feb 1;14(1):404. doi: 10.1038/s41467-023-36030-0.

Authors

Yan Chong^{1

2

3

4}, Reza Gholizadeh², Tomohito Tsuru^{5

6}, Ruopeng Zhang^{1

4}, Koji Inoue⁷, Wenqiang Gao⁸, Andy Godfrey⁸, Masatoshi Mitsuhara⁹, J W Morris Jr¹, Andrew M Minor^{10

11}, Nobuhiro Tsuji^{12

13}

Affiliations

¹ Department of Materials Science and Engineering, University of California, Berkeley, CA, USA.
² Department of Materials Science and Engineering, Kyoto University, Kyoto, Japan.
³ Elements Strategy Initiative for Structural Materials (ESISM), Kyoto University, Kyoto, Japan.
⁴ National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
⁵ Elements Strategy Initiative for Structural Materials (ESISM), Kyoto University, Kyoto, Japan. tsuru.tomohito@jaea.go.jp.
⁶ Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Tokai-mura, Ibaraki, Japan. tsuru.tomohito@jaea.go.jp.
⁷ Institute for Materials Research, Tohoku University, Oarai, Ibaraki, Japan.
⁸ Key Laboratory of Advanced Materials (MoE), School of Materials Science and Engineering, Tsinghua University, Beijing, China.
⁹ Department of Advanced Materials Science and Engineering, Kyushu University, Fukuoka, Japan.
¹⁰ Department of Materials Science and Engineering, University of California, Berkeley, CA, USA. aminor@berkeley.edu.
¹¹ National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, USA. aminor@berkeley.edu.
¹² Department of Materials Science and Engineering, Kyoto University, Kyoto, Japan. tsuji.nobuhiro.5a@kyoto-u.ac.jp.
¹³ Elements Strategy Initiative for Structural Materials (ESISM), Kyoto University, Kyoto, Japan. tsuji.nobuhiro.5a@kyoto-u.ac.jp.

Abstract

Interstitial oxygen embrittles titanium, particularly at cryogenic temperatures, which necessitates a stringent control of oxygen content in fabricating titanium and its alloys. Here, we propose a structural strategy, via grain refinement, to alleviate this problem. Compared to a coarse-grained counterpart that is extremely brittle at 77 K, the uniform elongation of an ultrafine-grained (UFG) microstructure (grain size ~ 2.0 µm) in Ti-0.3wt.%O is successfully increased by an order of magnitude, maintaining an ultrahigh yield strength inherent to the UFG microstructure. This unique strength-ductility synergy in UFG Ti-0.3wt.%O is achieved via the combined effects of diluted grain boundary segregation of oxygen that helps to improve the grain boundary cohesive energy and enhanced <c + a> dislocation activities that contribute to the excellent strain hardening ability. The present strategy will not only boost the potential applications of high strength Ti-O alloys at low temperatures, but can also be applied to other alloy systems, where interstitial solution hardening results into an undesirable loss of ductility.