Ductile iron

In October 1949 Keith Dwight Millis, Albert Paul Gagnebin and Norman Boden Pilling, all working for INCO, received U.S. patent 2,485,760 on a cast ferrous alloy using magnesium for ductile iron production.

Whereas sharp graphite flakes create stress concentration points within the metal matrix, rounded nodules inhibit the creation of cracks, thus providing the enhanced ductility that gives the alloy its name.

[citation needed] Elements such as copper or tin may be added to increase tensile and yield strength while simultaneously reducing ductility.

Improved corrosion resistance can be achieved by replacing 15–30% of the iron in the alloy with varying amounts of nickel, copper, or chromium.

It competes with polymeric materials such as PVC, HDPE, LDPE and polypropylene, which are all much lighter than steel or ductile iron; being softer and weaker, these require protection from physical damage.