Thermal and microstructural characterization of a novel ductile cast iron mod-ified by aluminum addition

• Published in: 矿物冶金与材料学报 Vol. 27; no. 2; pp. 190 - 199
• Main Authors: Gül?ah Akta? ?elik, Maria-Ioanna T. Tzini, eyda Polat, Hakan Atapek, Gregory N. Haidemenopoulos
• Format: Journal Article
• Language: English
• Published: Department of Metallurgical and Materials Engineering, Kocaeli University, Kocaeli 41001, Turkey%Laboratory of Materials, Department of Mechanical Engineering, University of Thessaly, Volos 38334, Greece%Laboratory of Materials, Department of Mechanical Engineering, University of Thessaly, Volos 38334, Greece 2020; Department of Mechanical Engineering, Khalifa University of Science and Technology, Abu Dhabi 127788, UAE
• Subjects: alloy design; high-temperature material; ductile cast iron; Thermo-Calc
• ISSN: 1674-4799; 1869-103X

In high-temperature applications, like exhaust manifolds, cast irons with a ferritic matrix are mostly used. However, the increasing de-mand for higher-temperature applications has led manufacturers to use additional expensive materials such as stainless steels and Ni-resist austen-itic ductile cast irons. Thus, in order to meet the demand while using low-cost materials, new alloys with improved high-temperature strength and oxidation resistance must be developed. In this study, thermodynamic calculations with Thermo-Calc software were applied to study a novel ductile cast iron with a composition of 3.5wt％ C, 4wt％ Si, 1wt％ Nb, 0–4wt％ Al. The designed compositions were cast, and thermal analysis and microstructural characterization were performed to validate the calculations. The lowest critical temperature of austenite to pearlite eutectoid transformation, i.e., A1, was calculated, and the solidification sequence was determined. Both calculations and experimental data revealed the im-portance of aluminum addition, as the A1 increased by increasing the aluminum content in the alloys, indicating the possibility of utilizing the al-loys at higher temperature. The experimental data validated the transformation temperature during solidification and at the solid state and con-firmed the equilibrium phases at room temperature as ferrite, graphite, and MC-type carbides.