The Story of Nitinol

The shape-retaining alloy Nitinol (Nickel Titanium Naval Ordance Laboratory), the “metal with a memory,” is revolutionizing manufacturing, engineering, and medicine as countless products that “think” for themselves enter the marketplace. This article recounts its discovery in 1959 by William J. Buehler of the U.S. Naval Ordnance Laboratory, its subsequent development by Buehler and Frederick E. Wang, and its applications in orthopedic and cardiovascular surger, orthodontics, solid-state heat engines, “shrink-to-fit” pipe couplers for aircraft, safety products, eyeglass frames, and toys. The serendipitous nature of the discovery, the solid-to-solid (austenite to martensite) phase transition that produces the alloy’s unusual properties, its numerous practical applications, and the ready availability of samples make the alloy an ideal, exciting, and thought-provoking topic for chemistry courses at all levels in both lecture and laboratory.