Cast iron where graphite forms nodular spheroids, providing high ductility.
Core Principles & Analysis
It was invented in 1943 by Keith Millis at the International Nickel Company, who found magnesium additions make graphite grow as spheres instead of flakes.
Nodular graphite removes the stress-concentrating flake tips of grey iron, giving ferritic grades tensile elongations above 18%.
It dominates pressurized water and sewer pipe, and massive ductile iron castings form wind turbine hubs and diesel crankshafts.