A new ‘designer’ titanium alloy is made using 3D printing

(Nanowerk News) A research team has created a new class of titanium alloy that is strong and not brittle under tension, by integrating alloy and 3D printing process design.

Breakthrough, published in Natural (“Strong and ductile titanium-oxygen-iron alloy with additive manufacturing”), can help broaden the applications of titanium alloys, improve sustainability, and drive innovative alloy designs.

Their findings hold promise for a new class of high-performance titanium alloys that are more sustainable for applications in aerospace, biomedical, chemical engineering, aerospace and energy technology.

RMIT University and the University of Sydney are leading the innovation, working with Hong Kong Polytechnic University and Melbourne company Hexagon Manufacturing Intelligence.

Lead researcher Professor Ma Qian of RMIT said the team instilled circular economy thinking into their design, creating great promise for producing their new titanium alloy from industrial waste and low-grade materials.

“Reusing waste and low quality materials has the potential to add economic value and reduce the high carbon footprint of the titanium industry,” said Qian of RMIT’s Center for Additive Manufacturing in the School of Engineering.

What kind of titanium alloy does the team make?

The team’s titanium alloy is composed of a mixture of two crystalline forms of titanium, called the alpha-titanium phase and the beta-titanium phase, each corresponding to a specific atomic arrangement.

This alloy class has become the backbone of the titanium industry. Since 1954, this alloy has been produced mainly by adding aluminum and vanadium to titanium.

The research team investigated the use of oxygen and iron – the two most powerful stabilizers and enhancers of the alpha and beta-titanium phases – which are abundant and inexpensive.

Two challenges have hindered the development of strong and ductile alpha-beta titanium-oxygen-iron alloys through conventional manufacturing processes, Qian said.

“One of the challenges is that oxygen – colloquially known as ‘kryptonite to titanium’ – can make titanium brittle, and another is that adding iron can cause serious defects in the form of large patches of beta-titanium.”

The team used Laser Directed Energy Deposition (L-DED), a 3D printing process suitable for making large, complex parts, to print the alloy from metal powder.

“The main driver for us is the combination of our alloy design concept with 3D printing process design, which has identified a series of alloys that are strong, ductile and easy to print,” said Qian.

The attractive properties of this new alloy that can rival commercial alloys are associated with its microstructure, said the team.

“This research provides a novel titanium alloy system capable of broad and tunable mechanical properties, high manufacturability, great potential for emission reductions and insights for material design in such systems,” said one of the principal investigators at the University of Sydney Pro-Vice-Chancellor. Professor Simon Ringer.

“An important driver is the unique distribution of oxygen and iron atoms within and between the alpha-titanium and beta-titanium phases.

“We have engineered a nanoscale gradient of oxygen in the alpha-titanium phase, featuring strong high-oxygen segments, and ductile low-oxygen segments allowing us to exercise control over local atomic bonding thereby reducing the potential for brittleness.”

What are the potential applications of the research findings?

Lead author Dr Tingting Song, RMIT Vice-Chancellor Research Fellow, said the team is “at the start of a big journey, from our new proof of concept here, to industrial applications”.

“There is reason to be excited – 3D printing offers a fundamentally different way of creating new alloys and has distinct advantages over traditional approaches,” he said.

“There is a potential opportunity for the industry to reuse waste spongy titanium-oxygen-iron alloys, recycled ‘off-spec’ high-oxygen titanium powder, or titanium powder made from spent high-oxygen titanium using our approach.”

Co-author Dr Zibin Chen, who joined Hong Kong Polytechnic University from the University of Sydney in the final stages of the collaboration, said the research had wider implications.

“Oxygen embrittlement is a major metallurgical challenge not only for titanium, but also for other important metals such as zirconium, niobium and molybdenum and their alloys,” he said.

“Our work can provide a template for reducing this oxygen embrittlement problem through 3D printing and microstructural design.”