The role of nanoscale heterogeneous structure in simultaneously enhancing strength and ductility of high-oxygen Ti–6Al–4V alloy

ABSTRACT

A high-oxygen (∼0.5 wt-%) Ti–6Al–4V alloy with a nanoscale heterogeneous structure consisting of ultrathin-lamellar-structured and coarse-grained domains was fabricated by powder processing and thermomechanical consolidation. In investigating the effect of heat treatment on this alloy, it was found that changing such nanoscale heterogeneous structure into a regular α/β lamellar structure, which was commonly produced in conventional fabrication routes, caused not only a significant decrease of strength but also a clear drop in tensile ductility. Analysis revealed that the intrinsic plasticity of coarse-grained domains and deformation coordination across domain boundaries captured microcracks and increased strain hardening rate, leading to the enhanced ductility of heterogeneous structure. In contrast, the intergranular fracture mode and inadequate variation of crystallographic orientations of α lamellae were ductility-deterioration mechanisms for the regular lamellar structure.

KEYWORDS:

• Titanium alloy
• powder metallurgy
• microstructure
• tensile properties
• oxygen content

Acknowledgements

We wished to extend our thanks to Mrs. Xinqiu Guo for her helpful discussion.

Disclosure statement

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

Additional information

Funding

his work was supported by National Natural Science Foundation of China [Grant number 51971143] and The National Key Research and Development Program of China [Grant number 2017-VI-0013-0085].

Notes on contributors

Yifei Luo

Yifei Luo received his Bachelor degree in Metallurgical Engineering from Northeastern University, China. He is currently a PhD candidate at Shanghai Jiao Tong University.

Zhen Zhang

Zhen Zhang received the Master degree at University of New South Wales, Australia. He is currently a PhD candidate at Shanghai Jiao Tong University.

Yuehuang Xie

Yuehuang Xie received a PhD degree in Materials Science and Engineering in 2020 from Shanghai Jiao Tong University.

Jiamiao Liang

Jiamiao Liang is an engineer at Shanghai Jiao Tong University, where he obtained the PhD degree in Materials Science and Engineering in 2016.

Deliang Zhang

Deliang Zhang is a distinguished professor in School of Materials Science and Engineering in Northeastern University, China. He received the PhD degree from Oxford University and subsequently worked as a postdoctoral research fellow at Oxford University and Carnegie Mellon University. Since then he has worked as a research academic at University of Queensland (1993–1996), University of Waikato (1996–2013), Shanghai Jiao Tong University (2010–2016) and Northeastern University (since 2016).