Duplex stainless steels are called “duplex” because they have a two-phase microstructure consisting of grains of ferritic and austenitic stainless steel. They have significantly better toughness and ductility than ferritic grades; about twice as strong as regular austenitic or ferritic stainless steels ,a range of corrosion resistance, similar to the range for austenitic stainless steels and show very good stress corrosion cracking.