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> Buehler was looking at alloys with two solid states as possible materials for the nose cone. He had selected roughly 60 alloys for further examination from a book entitled Constitution of Binary Alloys–nitinol being one of them. When he made the ingots for testing, he intentionally dropped one of the cold ones on the floor. Hoping to hear a clear bell-like ring, indicating that the metal had the properties he was hoping for. Instead, it returned a dull thud–similar to dropping a sack of flour on the ground. Worried that the ingot was filled with internal flaws, he dropped one of the ingots that hadn’t cooled yet. This returned a wonderful bell-like ring. However, after the ingot had been cooled in water, it returned a dull, leaden thud, just like the first one. This is the first indication that nitinol had a substantially different double state. Buehler named his alloy nitinol for Nickel-Titanium Naval Ordinance Laboratories. All of this occurred in 1959. However, the shape memory aspect of nitinol wasn’t discovered until a lab meeting in 1961. Buehler had been performing tests to determine the fatigue life of nitinol by bending a strip into an accordion like shape over and over again. His project was brought under review and his technician was demonstrating the fatigue properties to senior officials. During this presentation, one of the officials present heated the nitinol with a lighter, at which point it rapidly straightened out. This, of course, sent ripples throughout the scientific community. This material could take low grade heat and generate mechanical energy! Numerous scientists began experimenting with how to build engines with nitinol that would take low grade energy and transform it into very high grade energy that could be used to do work. This culminated in the Nitinol Heat Engine Conference, hosted by the Naval Surface Weapons Center (previously Naval Ordinance Labs) in 1974. At the Nitinol Heat Engine Conference, the NSWC gathered together the top scientists who had been working on nitinol to discuss what had been done and what still needed to be done to make nitinol heat engines a reality. The presentations from this conference are available in the book Proceedings of the Nitinol Heat Engine Conference. At this point, the activity surrounding nitinol seemed to all but dry up and disappear. Prior to the conference, nitinol researchers were featured on news channels like CNN and BBC. Afterwards, there was little to no attention given to nitinol by major television networks for over twenty years. This led to all kinds of conspiracy theories ranging from nitinol being kept for top secret government experiments to nitinol being an alien technology that was discovered in the Roswell accident. However, the reality is very different. Behind the scenes, material scientists were working hard to figure out HOW nitinol worked.

> In order to fully optimize a nitinol heat engine, it must be understood what happens when nitinol undergoes the shape memory effect. This will be discussed in greater detail in chapter 2. The next time nitinol appeared in public, it wasn’t referred to as nitinol, it was called just plain titanium. Of course, this is a misnomer since nitinol is slightly more nickel than titanium. This new public appearance didn’t even exhibit the shape memory effect as people were so excited about earlier. No, this was completely different and it was marketed under the trade name FlexonÒby the company Marchon Eyewear. Released for public sale in 1995, Flexonâwas unusual in that you could bend it through incredible distortions and it would just snap back to its original shape once you released it. Once Nike began to use it in their Vision line of glasses, athletes everywhere began buying it up. Gone were the days of breaking your glasses on a regular basis just because you lived an active lifestyle. You could sit on them, you could intentionally bend them, you could tackle someone in football, and they would just bounce back. These glasses would forgive those bumps and bangs over and over again–seemingly forever. People who broke their glasses every six months now could go several years on a single frame. The frames were termed ‘superelastic’. Once superelastic nitinol was discovered, it wasn’t long before surgeons began using it as they worked on people. Vascular stents was one of the first applications because the stent could be folded so flat that it could be inserted through the tiniest of holes into the patient’s bloodstream–minimizing recovery time. Once in place, the superelastic nitinol wire could withstand severe deformation and outlast stainless steel by an order of magnitude. To put this in perspective, superelastic nitinol stents were capable of undergoing a 30% deformation with a cycles to failure life expectancy greater than 10,000,000. Stainless steel, on the other hand, could withstand a deformation of just 0.5% with fatigue life of around 1 million cycles.