The aim of this study was to investigate the influence of austempering on the mechanical properties of solutionstrengthened ferritic cast ductile irons. The microstructural examinations of the samples were conducted using optical microscopy, scanning electron microscopy, and X-ray diffraction. Hardness, impact, and tensile tests were performed to determine the mechanical features. After the impact test, the fracture surface morphology was analyzed with scanning electron microscopy. The austempering results showed that the matrix structure with 70% ferrite and 30% bainite had the highest fracture toughness and yield strength. The ausferrite phase in microstructure played a positive role in ductility, toughness, and strain rates. The mechanical properties were strongly related to the amounts of ausferrite and retained ferrite ratio.
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