Grain refinement in titanium prevents low temperature oxygen embrittlement

• Published in: Nature communications Vol. 14; no. 1; pp. 404 - 11
• Main Authors: Chong, Yan, Gholizadeh, Reza, Tsuru, Tomohito, Zhang, Ruopeng, Inoue, Koji, Gao, Wenqiang, Godfrey, Andy, Mitsuhara, Masatoshi, Morris, J. W., Minor, Andrew M., Tsuji, Nobuhiro
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.02.2023; Nature Publishing Group; Nature Portfolio
• Subjects: 119/118; 639/301/1023/1026; 639/301/1023/303; Alloy systems; Alloys; Cryogenic temperature; Ductility; Elongation; Grain boundaries; Grain Boundary Segregation; Grain refinement; Grain size; High strength alloys; Humanities and Social Sciences; Interstitial solutions; Low temperature; MATERIALS SCIENCE; Microstructure; multidisciplinary; Oxygen; Oxygen content; Science; Science (multidisciplinary); Solution strengthening; Strain hardening; Titanium; Titanium base alloys; Ultrafines
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-023-36030-0

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. Oxygen has long been considered as a detrimental impurity in pure titanium since it can severely deteriorate the ductility. Here, the authors propose a simple, yet effective strategy via grain refinement to solve this long-standing issue, while preserving its potential hardening effect.