A net-shape forming process of Ti–6Al–4V sphere joints

ABSTRACT

Near-net shape forming of the hollow sphere joints (60 mm in diameter) used in large space truss structure of spacecraft was realised by powder injection molding and diffusion bonding. For metal injection molding (MIM) process, two binder systems based on polyoxymethylene (POM) and paraffin wax (PW) are comparatively studied. The powder loading, power law index, viscous flow activation energy and integrated rheological factors of feedstock were systematically studied. Except powder loading, The feedstock based on POM system has a smaller strain and temperature sensitivity (n = 0.368, E = 17.95 kJ mol⁻¹) and better rheological properties (α = 6.3). The lowest interstitials contents of as-sintered samples are 0.05 wt-% for C, 0.28 wt-% for O and 0.046 wt-% for N, which meet the Grade 5 PM (Ti–6Al–4V) specifications according to ASTM B988-13. The tensile strength and ductility reach 978 MPa and 6.3%, respectively, after 1300 °C sintering and capsule-free hot isostatic pressing (HIP).

KEYWORDS:

• Titanium alloys
• hollow sphere joints
• powder injection molding
• microstructure
• mechanical properties

Acknowledgements

This research work is supported by the National Natural Science Foundation of China (51922004, 51874037), State Key Lab of Advanced Metals and Materials, University of Science and Technology Beijing (2019-Z14,2020Z-04), Fundamental Research Funds for the Central Universities (FRF-TP-19005C1Z).

Disclosure statement

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

Additional information

Funding

This work was supported by the National Natural Science Foundation of China: [grant number 51922004, 51874037].

Notes on contributors

Ce Zhang

Ce Zhang received a PhD degree in 2020 Now he is postdoctor in University of Science and Technology Beijing.

Yu Pan

Yu Pan is a doctoral student in University of Science and Technology Beijing.

Jianzhuo Sun

Jianzhuo Sun is a doctoral student in University of Science and Technology Beijing.

Xin Lu

Xin Lu is a distinguished professor in University of Science and Technology Beijing. She is an expert in the field of powder metallurgy titanium alloys.

Jiazhen Zhang

Jiazhen Zhang is a part-time Professor of University of Science and Technology Beijing. He is also a deputy chief engineer of COMAC Beijing Research Center.