Australian scientists create new class of titanium alloys

Alloy 3D-printed from metal powder rivals the conventional ‘magic metal’ – used in aerospace and biomedical engineering – for strength and sustainability

Scientists have created a new class of titanium alloys using laser 3D printing, which they say could improve the sustainability of the titanium industry and be used in aerospace and biomedical engineering.

Titanium is a key metal in many industries and is prized for its high strength, lightness and durability.

Prof Ma Qian of RMIT University in Melbourne, who led the new alloy development, described titanium as "a magic metal".

"It's biocompatible and every year more than 1,000 tonnes of titanium metal is made into bone implants [globally]," he said. More corrosion-resistant than stainless steel in seawater, it is also used widely in submarines and desalination plants.

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"Without titanium alloys, we wouldn't be able to fly as we can today," Qian said, adding that titanium constitutes about 20% of the weight of a typical aircraft.

The mainstay of the titanium industry is an alloy known as Ti-6Al-4V, which contains 6% aluminium and 4% vanadium. Invented in 1954, this single alloy accounts for more than 50% of the entire market of titanium, Qian said.

The new alloy, 3D-printed from metal powder, does away with the need for aluminium and vanadium, using the readily abundant elements oxygen and iron instead, which are also cheaper to source.

Alloys with a high oxygen and iron content have traditionally been considered scrap titanium. The presence of oxygen can make the metal brittle – often referred to as the "kryptonite of titanium" – while iron has a tendency to segregate into defect flecks.

Using 3D printing, however, allowed the scientists to produce nanoscale-sized titanium crystals within the alloy and to carefully control the distribution of oxygen and iron atoms. As a result, some parts of the alloy are stronger and others more ductile (able to be drawn into wire) – and the material is not brittle under tension.

The new material rivals conventional titanium alloys in strength, said co-lead researcher Prof Simon Ringer, who is also pro-vice-chancellor at the University of Sydney.

One advantage of the 3D-printed alloy was the ability to tweak parameters during production to give the material "gradient properties", Ringer said. "You can build a thing that would have certain properties in one bit and other properties in another bit."

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Sustainability is another advantage, the researchers say, because titanium with a high iron and oxygen content could be recycled into the new alloy.

Having established the proof of concept, the researchers are still some way off industrial applications, such as in biomedical implants, and in the space and aerospace industries.

Advanced manufacturing and materials technology is one of seven fields that the federal government recently included on its list of critical technologies.

"Australia is No 1 in terms of the amount of reserves of titanium minerals in the world," Ringer said. "Many of us engineers in Australia are really excited about the opportunity that advanced manufacturing is creating for onshoring of production."

The study was published in the journal Nature.