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Chemical Industry and Chemical Engineering Quarterly 2022 Volume 28, Issue 2, Pages: 161-167
https://doi.org/10.2298/CICEQ201222027J
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Microstructure and fracture mode of unalloyed dual-phase austempered ductile iron

Janjatović Petar D. ORCID iD icon (Department of Production Engineering, Faculty of Technical Science, University of Novi Sad, Novi Sad, Serbia)
Erić-Cekić Olivera A. ORCID iD icon (Innovation Center of Mechanical Engineering Faculty, University of Belgrade, Belgrade, Serbia + Faculty of Mechanical and Civil Engineering, University of Kragujevac, Kraljevo, Serbia), olivera66eric@gmail.com
Rajnović Dragan M. ORCID iD icon (Department of Production Engineering, Faculty of Technical Science, University of Novi Sad, Novi Sad, Serbia)
Baloš Sebastian S. ORCID iD icon (Department of Production Engineering, Faculty of Technical Science, University of Novi Sad, Novi Sad, Serbia)
Grabulov Vencislav K. (Institute for testing of materials-IMS, Belgrade, Serbia)
Šiđanin Leposava P. (Department of Production Engineering, Faculty of Technical Science, University of Novi Sad, Novi Sad, Serbia)

Dual-phase ADI material microstructure consists of different amounts and morphologies of ausferrite and free ferrite, obtained by subjecting ductile iron to specific heat treatment. Its strength is lower compared to comparable ADI materials but exhibits a higher ductility, the major disadvantage of ADI. In the current study, an unalloyed ductile iron was intercritical austenitized in two-phase regions (α+Ƴ) at four temperatures from 840 to 780 °C for 2 h and austempered at 400 °C for 1 h to obtain dual-phase ADI with different percentages of free ferrite and ausferrite. Light and scanning electron microscopy was performed for the metallographic and fracture studies, respectively. Microscopy results were correlated to tensile testing results. The results indicated that, as the amount of ausferrite present in the matrix increases, higher values of strength and lower ductility are obtained. The fracture surfaces of dual-phase ADI microstructures with 22.8% of ausferrite in their matrix have regions of quasi-cleavage fracture around last-to-freeze zones, related to the presence of ausferrite in those areas. The specimens with the highest values of ausferrite of 86.8% among the dual-phase microstructure have a dominant quasi-cleavage type of fracture.

Keywords: dual matrix structure, austempered ductile iron, microstructure, surface of fracture

Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 451-03-68/2020-14/200156

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