Influence of Nickel on Microstructure and Property in Die-Cast Ductile Iron

Information from the abstract

This study examines the influence of nickel (Ni) additions on the microstructure and hardness of Ductile Iron (DI) produced in permanent molds, where higher cooling rates significantly affect solidification behavior. Ductile iron melts were prepared in a 100-kg induction furnace with varying Ni levels (0.06–12.30 wt.%), and Y-block castings were produced in accordance with ASTM A536. Optical microscopy and image analysis were employed to evaluate graphite morphology and matrix phases, while color etching was used to differentiate bainite and martensite. Results show that increasing Ni reduced the nodule count but promoted the formation of primary graphite due to hypereutectic solidification. The matrix evolved sequentially from ferrite to pearlite, and then to bainite and martensite with higher Ni content. At Ni levels above 9–12 wt.%, retained austenite was observed. Hardness increased with Ni additions up to ~10 wt.% but decreased slightly at higher contents due to the presence of retained austenite. These findings demonstrate that controlled Ni additions can produce ductile iron with comparable hardness to the Austempered Ductile Iron (ADI) without heat treatment.

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Related topics: Microstructure and Mechanical Properties of Steels · Metallurgical Processes and Thermodynamics · Powder Metallurgy Techniques and Materials