Effect of In-mold Al, Ti and Ca Additions on Austenite Morphology, Grain Size and Mechanical Properties of Nickel-Alloyed Ductile Iron

This research investigates the impact of in-mold additions of Al, Ti and Ca on the austenite morphology, grain size and mechanical properties of nickel-alloyed ductile iron. A hypoeutectic alloy with primary austenite phase was designed using thermodynamic calculations. Different alloying additions were placed into separate molds prior to the pour. Castings with various additions were produced for assessing their impact on the macrostructure, microstructure and tensile properties. Macrostructural analysis revealed the austenite grain structure. Microstructural examination with a scanning electron microscope (SEM) equipped with energy-dispersive X-ray and automated feature analysis was used to classify the non-metallic inclusions dispersed in the matrix of the cast samples. Thermal analysis was utilized to reveal the solidification characteristic temperatures and tensile tests were performed. The results indicated effects of different additions on the austenite grain structure and resultant impacts on the mechanical properties of the nickel-alloyed ductile irons.