Titanium-gold alloy four times harder than most steels

Titanium is the leading material for artificial knee and hip joints because it's strong, wear-resistant and nontoxic, but an unexpected discovery by Rice University physicists shows that the gold standard for artificial joints can be improved with the addition of some actual gold.
A new study in Science Advances describes the properties of a 3-to-1 mixture of titanium and gold with a specific atomic structure that imparts hardness.
According to the authors of the study, this alloy is about 3-4 times harder than most steels and four times harder than pure titanium, which is what's currently being used in most dental implants and replacement joints.
Most important, this compound is not difficult to make, and it's not a new material.
In fact, the atomic structure of the material—its atoms are tightly packed in a "cubic" crystalline structure that's often associated with hardness—was previously known. It's not even clear that Rice University scientists were the first to make a pure sample of the ultrahard "beta" form of the compound. But due to a couple of lucky breaks, they and their co-authors are the first to document the material's remarkable properties.

http://phys.org/news/2016-07-lab-titanium-gold-alloy-harder-steels.html