New titanium gold alloy four times harder than most steels

Rice university researchers say new allow could set new standard for bio-medical implants.

2 July 27, 2016
by Design Engineering staff

Crystal structure of beta titanium-3 gold (image credit: Rice University)

Crystal structure of beta titanium-3 gold (image credit: Rice University)

Physicists at Rice University have published a study on a new titanium and gold alloy that is not only significantly harder than most grades of steal as well as titanium alone, but also wear-resistant and highly bio-compatible.

“It is about 3-4 times harder than most steels,” said Emilia Morosan, the lead scientist on a new study in Science Advances that describes the properties of a 3-to-1 mixture of titanium and gold with a specific atomic structure that imparts hardness. “It’s four times harder than pure titanium, which is what’s currently being used in most dental implants and replacement joints.”

Morosan, a physicist who specializes in the design and synthesis of compounds with exotic electronic and magnetic properties, said the new study is “a first for me in a number of ways. This compound is not difficult to make, and it’s not a new material.”

While easy to create, the researchers say the material’s almost pure crystalline structure makes is surprisingly hard to destroy. During an experiment on a number of titanium/gold alloys, the team found the titanium-3-gold alloy resistant to even its hardest grinding equipment.

“When we tried to grind up titanium-gold, we couldn’t,” she recalled. “I even bought a diamond (coated) mortar and pestle, and we still couldn’t grind it up.”

The key to the alloy’s resilience is that it was produced at relatively high temperature, which creates the beta form of the alloy (β-Ti3Au), the researchers say. At lower temperatures, the atoms tend to arrange in another cubic structure—the alpha form of titanium-3-gold—which is about as hard as regular titanium.

The obvious application of the alloy, researchers say, is for biomedical implants, where bio-compatibility and wear resistance are key. Working in conjunction with the University of Texas MD Anderson Cancer Center in Houston, the team determined that the new alloy was even more bio-compatible than pure titanium, as well as more wear resistance.

Morosan said she has no plans to become a materials scientist or dramatically alter her lab’s focus, but she said her group is planning to conduct follow-up tests to further investigate the crystal structure of beta titanium-3-gold and to see if chemical dopants might improve its hardness even further.
www.rice.edu



2 Comments » for New titanium gold alloy four times harder than most steels
  1. Justin Hetrick says:

    As a machinist I have several questions. If it is so hard that diamond can’t touch it, how can you make anything out of it? Have you tried making the Alpha form, machining it to the shape you need, then heat treating to the Beta form? I do think this is an interesting discovery.

    • Mike McLeod Mike McLeod says:

      Hi Justin: To get the answers to your questions, you may need to contact the researchers at Rice University. My guess is the beta form has to be melted and molded. After that, it would seem there are other metals that are harder that could be used to shape it. Also, I would assume that once the alpha form of the metal sets, it would take melting point heat to break that lattice to allow the beta variant to form. That’s just a guess though. I think the import of this discovery is that this metal is the hardest of the highly bio-compatible alloys, potentially opening the door for longer lasting hip replacements and such.

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