In this study, the effect of austenitizing temperatures and low-temperature isothermal heat treatment (below martensite start temperature) on the microstructure and mechanical properties of AISI 9254 high silicon spring steel has been investigated. Experimental studies show that ultra-fine carbide-free bainite, tempered martensite and carbon enriched retained austenite could be observed in isothermally heat-treated samples where the as-received sample consisted of fine pearlite. A high tensile strength of ~2060 MPa, a total elongation of ~8 %, and absorbed energy of 105 J were achieved in a commercial high-Si steel by austempering below the Ms temperature. A good combination of strength and ductility has been obtained in prolonged austempering below the martensite start temperature (225 °C) from an austenitizing temperature of 870 °C.
About the authors
Mr. Ömer Faruk Murathan was born in 1989, received his BSc from the Metallurgical and Materials Engineering Department, Faculty of Engineering, Atilim University, Ankara, Turkey, in 2013. He earned his MSc degrees at Gazi University, Ankara, Turkey in 2015. Currently, he is a PhD Student at the Department of Metallurgical and Materials Engineering, Faculty of Technology, Gazi University, Ankara, Turkey. His research interests are heat treatments of steel and cast iron.
Assist. Prof. Dr. Kemal Davut was born in 1982 and works at the at the Department of Metallurgical and Materials Engineering, Faculty of Engineering, Atilim University, Ankara, Turkey. He received his BSc and MSc degrees from the Department of Metallurgical and Materials Engineering, Middle East Technical University in 2004 and 2006, respectively. He earned his PhD degree in 2013 at the RWTH Aachen University. His areas of interest include crystallographic texture analysis, EBSD technique, SEM, quantitative metallography, magnetic Barkhausen noise, heat treatment of ferrous alloys and advanced high strength steels.
Assist. Prof. Dr. Volkan Kilicli was born in 1980 and works at the Department of Metallurgical and Materials Engineering, Faculty of Technology, Gazi University, Ankara, Turkey. He graduated in Metallurgy Education from Gazi University, Ankara, Turkey, in 2001. He received his MSc and PhD degrees from Gazi University, Ankara, Turkey in 2004 and 2010, respectively. His research interests include the heat treatment of steel and cast iron, semi-solid processing of aluminum alloys, self- healing metallic materials and metal matrix composites.
The authors wish to express their gratitude for the financial support of Gazi University Scientific Research Fund (Project code: GÜBAP 07/2013-01). The authors’ gratitude is also extended to the Metal Forming Center of Excellence at Atilim University for providing electron microscopy, X-RD and quenching dilatometer facilities.
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