Keith Millis

Keith Millis

Keith Dwight Millis (1915–1992) was an American metallurgical engineer and inventor of ductile iron.

Keith Millis grew up in Rensselaer, New York and earned his Bachelor of Science in Metallurgical Engineering as a 1938 graduate of Rensselaer Polytechnic Institute. A year later he was conferred a Master of Science degree in Metallurgical Engineering at RPI.

Early in the Second World War, chromium was considered critical to the war effort and experimentation was conducted by Millis to find a substitute. He made his discovery while experimenting with molten iron and magnesium. The original intent was to find another element that would cause all the carbon in the cast iron alloy to be combined as carbide. Magnesium was a known carbide former. Instead, the graphite in the iron formed into spheroidal shapes, and the cast iron had high tensile strength plus it exhibited ductility. Thus was born ductile iron in 1943.

Millis and others at the International Nickel Company (Inco) sought and obtained U.S. patent 2,485,760 on October 25, 1949 for magnesium additions to cast iron that would spheroidize the graphite and dramatically ductilize the material.

As an employee of Inco, Millis worked to promote the use of ductile iron as it began to be used as a commercial material. He also helped to found the Ductile Iron Society, and organization whose purpose is to promote the production and application of ductile iron castings.

Millis died in 1992.