Influence of defects on damage tolerance of Metal-Injection-Molded β titanium alloys under static and dynamic loading

ABSTRACT

The β titanium alloys are key materials in lightweight and biomedical applications, due to the combination of excellent biocompatibility and mechanical properties. However, the Binder-based Powder Technologies such as Metal-Injection-Molding (MIM), Binder-Jetting and Fused-Filament-Fabrication, normally introduce three major processing-related defects in the as-sintered Ti-parts: (i) residual porosity, (ii) high impurity level and (iii) coarse-grained structure. The previous studies revealed that these processing defects invariably tend to be even more severe in β titanium alloys than in α/β Ti-6Al-4V alloy, all fabricated by powder metallurgical route. In this work, these processing defects and their likely origins in MIM β titanium alloys are analysed. Furthermore, the influence of these defects on damage tolerance and fracture mechanisms of MIM β titanium alloys under either static or dynamic loading is investigated. Based on the studies, strategic technical improvements in the processing to improve the reliability of MIM β titanium alloys products are proposed.

KEYWORDS:

• Powder metallurgy
• metal-injection-molding
• sintering
• titanium alloy
• defect
• mechanical property
• fracture mechanism

Acknowledgements

And authors would like to thank W. Limberg, A. Dobernowsky, K. Erdmann, S. Riekehr, Dr. N. Kashaev and C. Horstmann for their technical help in materials processing and mechanical testing. In addition, Dr. P. Xu wants to thank, the two most important people in his educational experience, Dr. Thomas Ebel and Mrs. Lijun Ren.

Disclosure statement

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

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

The authors acknowledge the financial support of the National Natural Science Foundation of China [grant number 32071327]; the Science and Technology Program of Shaanxi Province [grant number 2021ZDLSF03-11].

Notes on contributors

Peng Xu

Peng Xu (Pöng Schü) is currently an associate scientist and a senior engineer at Northwest Academy of Nonferrous Metals, Xi'an, China. He did his PhD program at Helmholtz-Zentrum Hereon (formerly Helmholtz Forschungszentrum GKSS) and later worked as a research fellow there. He has studied beta titanium alloys of metal-injection-molding and sinter-based additive manufacturing for seven years as well as contributed six scientific papers, as the first and corresponding author, being published in Applied Materials Today, Materials & Design, etc. He is also a Keynote presenter at Euro PM2021 Congress & Exhibition.

Thomas Ebel

Dr. Thomas Ebel studied Physics at Hamburg University, Germany, and got his PhD title for a fundamental study in materials science by neutron scattering. After his post-doc time, he worked ten years in a medical company and focused on Metal Injection Moulding of titanium alloys. 2006 he returned to research and since then is head of department in the Institute of Metallic Biomaterials of the public research centre Hereon in Germany. Focus of his work is processing of titanium and magnesium powders for the manufacture of novel medical implants. This includes both the technical side and the scientific one, in particular how to achieve robust alloys and processes as well as high properties, in particular fatigue properties. Dr. Thomas Ebel acts as reviewer for scientific journals, published three book chapters on MIM of titanium and supervised several PhD students. Furthermore, he is member of several committees organising powder metallurgical conferences.

Florian Pyczak

Florian Pyczak earned his doctorate in Materials Science and Engineering from the Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany, in 2002. After working as a research assistant until 2008 at the Friedrich-Alexander-Universität specialising in the research of superalloys he went to Helmholtz-Zentrum Hereon in Geesthacht, Germany. There as head of department of Metal Physics he broadened his research portfolio to alloy and process development of intermetallic TiAl alloys, light metals and Co-base superalloys. A special focus of his research is microstructure characterisation by electron microscopy and high energy X-ray diffraction as well as powder metallurgy of Ti- and TiAl-based materials. Since 2009 he holds a professorship for ‘Microstructure based materials design’ at the Brandenburgisch Technische Universität Cottbus-Senftenberg, Germany.

Regine Willumeit-Römer

Regine Willumeit-Römer holds a professorship for „Biological interfaces of implants“ at the Faculty of Engineering, Christian-Albrechts-University Kiel, Germany, and she is the director of the Institute of Metallic Biomaterials at Helmholtz-Zentrum Hereon, Germany. From 1985 to 1996, she studied physics at the University of Hamburg, where she obtained her university diploma and doctorate. She has been responsible for a variety of research projects ranging from utilizing neutron and synchrotron radiation in structure determination of biomolecules and materials to the development of degradable Mg-based implant materials. She coordinated third party projects totalling more than 16 million euros and published more than 300 scientific articles.

Sen Yu

Prof. Sen Yu is the head of Biomaterials Research Center at Northwest Institute for Non-ferrous Metal Research, the chief of Shaanxi Key Laboratory of Biomedical Metallic Materials, and the director of China-Australia Joint Research Centre for Biomedical Metallic Materials. He has been active in medical biomaterials for more than 15 years and is the author of 120+ publications, 50+ inventional patents, and 5 provincial/ministerial awards. He has hosted and participated in approximately 40 research projects with a total fund of more than 40 million CNY (ca. $6MM).