Researchers develop new titanium alloys for aerospace, biomedical, and other applications

A team of researchers, in collaboration with RMIT University, the University of Sydney, Hong Kong Polytechnic University, and Hexagon Manufacturing Intelligence, has made a significant breakthrough in the field of titanium alloys. Their findings, recently published in the journal Nature, introduce a new class of titanium alloys that possess both strength and resilience under tension. This development has the potential to expand the applications of titanium alloys, enhance sustainability, and drive innovative alloy design.

The lead researcher, Professor Ma Qian from RMIT University’s Center for Additive Manufacturing in the School of Engineering, explained that the team incorporated circular economy principles into their design process. By doing so, they have opened up the possibility of producing these new titanium alloys using industrial waste and low-grade materials. This approach not only holds economic value but also has the potential to reduce the carbon footprint associated with the titanium industry.

The discovery of these sustainable and high-performance titanium alloys could revolutionize various industries such as aerospace, biomedical, chemical engineering, space, and energy technologies. With the ability to integrate alloy and 3D-printing process designs, these alloys demonstrate great promise for advancing materials science and promoting a more sustainable future.

The making of a titanium alloy on the laser 3D printer that the team used at for their research (note that this is not an alloy the team made for this particular research). Credit: RMIT

What type of titanium alloys has the team made?

In their groundbreaking research, the team focused on a novel approach to creating titanium alloys. Traditionally, titanium alloys have been composed of a combination of two distinct forms of titanium crystals: the alpha-titanium phase and the beta-titanium phase. These phases correspond to specific atomic arrangements within the alloy.

For over half a century, titanium alloys have been essential to the titanium industry. These alloys have typically been produced by introducing aluminum and vanadium into titanium. However, the research team sought to explore alternative methods by harnessing the power of oxygen and iron.

Both oxygen and iron are known for their exceptional stabilizing and strengthening properties when it comes to the alpha- and beta-titanium phases. Moreover, these elements are abundant and cost-effective. Recognizing these advantages, the team delved into the utilization of oxygen and iron as key components in their innovative alloy design.

By incorporating these abundant and affordable elements into their titanium alloys, the team has paved the way for a new generation of titanium materials with enhanced characteristics and potential applications across various industries.

Atomic-scale microstructure across an alpha-beta interphase interface from a new alloy 3D-printed by the team using laser directed energy deposition. Credit: Ma Qian, Simon Ringer and colleagues

The development of strong and ductile alpha-beta titanium-oxygen-iron alloys has faced two significant challenges within conventional manufacturing processes, as highlighted by Professor Qian. Firstly, the presence of oxygen, often referred to as ‘the kryptonite to titanium,’ can render titanium alloys brittle. Secondly, the addition of iron has the potential to cause serious defects in the form of large patches of beta-titanium.

To overcome these challenges, the research team employed Laser Directed Energy Deposition (L-DED), a 3D printing process well-suited for fabricating intricate and sizable components, to manufacture their alloys using metal powder.

The successful realization of these alloys with superior properties, comparable to commercial alloys, can be attributed to their unique microstructure, according to the team. The integration of alloy design concepts with 3D-printing process design proved to be a pivotal factor in identifying a range of alloys that exhibit strength, ductility, and excellent printability.

Co-lead researcher Professor Simon Ringer, the Pro-Vice-Chancellor of the University of Sydney, emphasized the significance of this research. He noted that the newly developed titanium alloy system offers a broad and adjustable spectrum of mechanical properties, exceptional manufacturability, substantial potential for reducing emissions, and valuable insights for materials design in related systems.

The key breakthrough lies in the precise distribution of oxygen and iron atoms within and between the alpha-titanium and beta-titanium phases. The researchers engineered a nanoscale gradient of oxygen in the alpha-titanium phase, featuring segments with high oxygen content that contribute to strength, and segments with low oxygen content that promote ductility. This control over local atomic bonding mitigates the risk of embrittlement and contributes to the alloy’s remarkable properties.

What are the potential applications of the research findings?

Dr. Tingting Song, the lead author of the study and a Vice-Chancellor’s Research Fellow at RMIT, expressed enthusiasm for the team’s findings and emphasized that they are embarking on a significant journey towards industrial applications. She highlighted the transformative potential of 3D printing, which offers distinct advantages over traditional manufacturing methods, making it a promising avenue for producing novel alloys.

Dr. Song also pointed out the possibility of utilizing waste sponge titanium-oxygen-iron alloys, recycled high-oxygen titanium powders that do not meet specifications, or titanium powders derived from high-oxygen scrap titanium using their approach. This presents an exciting opportunity for the industry to recycle and repurpose materials that would otherwise go to waste.

Co-lead author Dr. Zibin Chen, who joined Hong Kong Polytechnic University from the University of Sydney during the collaboration, emphasized the broader implications of their research. He explained that oxygen embrittlement is a significant challenge not only for titanium but also for other important metals such as zirconium, niobium, and molybdenum, as well as their alloys. The team’s work could serve as a blueprint for addressing oxygen embrittlement issues through the combination of 3D printing and microstructure design.

According to Professor Simon Ringer, the Pro-Vice-Chancellor of the University of Sydney, the team’s achievements were made possible through sustained investment in research infrastructure by national and state governments, as well as universities. He highlighted the success of Australia’s national collaborative research infrastructure strategy and expressed the potential for extending this strategy into the realm of advanced manufacturing.

The team’s research paper, titled “Strong and ductile titanium-oxygen-iron alloys by additive manufacturing,” has been published in the journal Nature. Additionally, an editorial on the team’s work, titled “Designer titanium alloys created using 3D printing,” is also published in Nature, further emphasizing the significance of their research.

Source: RMIT University

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