Effects of Titanium, Cerium or Aluminum Addition on Microstructure and Mechanical Properties of Ductile Iron Castings

Fineness of microstructural constituents in the metallic alloys affects their mechanical properties. This study sought to determine the effects of selected levels of titanium, cerium and aluminum on the fineness of microstructural constituents within ductile iron. A hypoeutectic iron was studied. Cerium additions in the amounts of 0.01 wt.% and 0.03 wt.%, titanium additions in the amounts of 0.02 wt.% and 0.04 wt.%, and aluminum addition at the amount of 0.02 wt.% were tested. The influences of the selected additions were determined using three methods: direct secondary dendrite arm spacing (SDAS) measurement, liquidus recalescence analysis and tensile testing. The results of the study showed that at above a critical value, cerium refined the SDAS effectively within a distance of 22 mm from the casting bottom surface, whereas for the locations with slower cooling rates, Ce did not refine microstructure and impaired elongation. Titanium had an adverse effect on refining the microstructure when Al-containing inoculant was used. The addition of Al was found effective at achieving a refined microstructure and improved mechanical properties. The inclusion composition and number density change as a result of alloy additions were measured.