Scientists from Rice University have created a new type of alloy, using a 3-to-1 mixture of titanium and gold, which could vastly improve the quality and durability of medical implants and prosthetics.
Because it is biocompatible (non-toxic) and resistant to wear, titanium is the standard material for medical prosthetics like artificial joints. Unfortunately, they eventually do wear down and require replacement every 10 years or so. In testing their new alloy, called beta-Ti3Au, Rice University researchers found it to be four times harder than pure titanium – suggesting it could be used to create prosthetics that last much longer. Since the alloy is extraordinarily strong, it could also have applications in mining, drilling, and safety equipment.
Since it is also biocompatible, it’s easy to imagine gold being used in new types of medical implants. However, gold is also the most malleable metal – which begs the question: how does gold combine with titanium to form such a strong alloy? The answer lies in the way the atoms of the alloy are arranged.
The researcher’s key discovery was not the idea to combine gold and titanium – it was the change that occurs when the metals are combined at higher temperatures. Combining the metals at a low temperature creates alpha-Ti3Au, a known alloy which has properties comparable to regular titanium. High temperatures cause the atoms to arrange into a more crystalline structure, creating the beta alloy. According to the research abstract, the alloy’s structure allows for “elevated valence electron density, reduced bond length, and pseudogap formation” – all of which increase its hardness.
Image attribution: Svanidze, Eteri, et al. “Fig. 2 Structural analysis of the Ti0.75Au0.25 alloy.” Figure. Science Advances, 20 July 2016, advances.sciencemag.org/content/2/7/e1600319.figures-only. Accessed 2016.