J. Mater. Sci. Technol. ›› 2021, Vol. 68: 112-123.DOI: 10.1016/j.jmst.2020.06.053

• Research Article • Previous Articles     Next Articles

Overcoming the strength-ductility trade-off by tailoring grain-boundary metastable Si-containing phase in β-type titanium alloy

X. Luoa, L.H. Liua, C. Yanga,*(), H.Z. Lua, H.W. Maa, Z. Wanga, D.D. Lic, L.C. Zhangd, Y.Y. Lia,b   

  1. a National Engineering Research Center of Near-net-shape Forming for Metallic Materials, South China University of Technology, Guangzhou, 510640, China
    b State Key Laboratory of Materials Processing and Die & Mould Technology, Huazhong University of Science and Technology, Wuhan, 430074, China
    c Key Laboratory of Automobile Materials of MOE, Department of Materials Science, Jilin University, Changchun, 130012, China
    d School of Engineering, Edith Cowan University, 270 Joondalup Drive, Joondalup, Perth, WA 6027, Australia
  • Received:2020-05-07 Revised:2020-05-29 Accepted:2020-06-09 Published:2021-03-30 Online:2021-05-01
  • Contact: C. Yang
  • About author:*E-mail address: cyang@scut.edu.cn (C. Yang).

Abstract:

It is well accepted that grain-boundary phases in metallic alloys greatly deteriorate the mechanical properties. In our work, we report on a novel strategy to prepare high strength-ductility β-type (Ti69.71Nb23.72Zr4.83Ta1.74)97Si3 (at.%) (TNZTS) alloys by tailoring grain-boundary metastable Si-containing phase. Specifically, the thin shell-shaped metastable S1 phase surrounding the columnar β-Ti grain was intercepted successfully via nonequilibrium rapid solidification achieved by selective laser melting (SLM). Subsequently, the thin shell-shaped metastable (Ti, Nb, Zr)5Si3 (called S1) phase was transformed into globular (Ti, Nb, Zr)2Si (called S2) phase by the solution heat treatment. Interestingly, the globular S2 phases reinforced TNZTS alloy exhibits ultrahigh yield strength of 978 MPa, ultimate strength of 1010 MPa and large elongation of 10.4 %, overcoming the strength-ductility trade-off of TNZTS alloys by various methods. Especially, the reported yield strength herein is ∼55 % higher than that of conventionally forged TNZT alloys. Dynamic analysis indicates the globularization process of the metastable S1 phase is controlled by the model of termination migration. The quantitative analysis on strengthening mechanism demonstrates that the increase in yield strength of the heat-treated alloys is mainly ascribed to the strengthening of the precipitated silicide and the dislocations induced by high cooling rate. The obtained results provide some basis guidelines for designing and fabricating β-titanium alloys with excellent mechanical properties, and pave the way for biomedical application of TNZTS alloy by SLM.

Key words: Selective laser melting, β titanium alloys, Heat treatment