Nitinol — an alloy of nickel and titanium — takes a long, hot journey from the Earth’s crust to the deepest parts of the human anatomy. It starts with ore heaved from deep mines undergound or stripped from the soil and refined into titanium and nickel.
To make raw nitinol, suppliers melt pure titanium — in the form of sponge or top-shelf crystal bar — with pure nickel. They must be combined at a roughly 1:1 atomic ratio, which comes out to around 55% nickel and 45% titanium. A nitinol at that ratio would be referred to as nitinol 55.
To be used for medical devices, the resulting nitinol should meet standards set by…