Development of a high strength high toughness ausferritic steel

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 513; pp. 329 - 339
• Main Authors: Putatunda, Susil K., Singar, Arjun V., Tackett, Ronald, Lawes, Gavin
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 15-07-2009; Elsevier
• Subjects: Applied sciences; Austempering; Austenite; Ductility; Elasticity. Plasticity; Exact sciences and technology; Ferrite; Fracture toughness; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Strain hardening exponent; Tensile strength; Austempering; Ferrite; Strain hardening exponent; Ductility; Austenite; Tensile strength; Fracture toughness; Heat treatment; Electrical properties; Austenitic ferritic steel; High strength steel; Mechanical properties; Metallography; X ray diffraction; Thermal properties; Plane strain; Yield strength; Microstructure
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2009.02.013

A new ausferritic steel with high strength and exceptionally high fracture toughness has been developed. This steel has been synthesized integrating concepts from Austempered Ductile Cast Iron (ADI) technology. The influence of the austempering temperature on the microstructure and mechanical properties of this steel at room temperature and ambient atmosphere has been examined. The effect of microstructure on the plane strain fracture toughness and on the magnetic, electrical, and thermal properties was also investigated.
Compact tension and cylindrical tensile specimens prepared from the low alloy medium carbon steel with high silicon content were initially austenitized at 927
°C for 2
h and then subsequently austempered at several temperatures between 260
°C (500
F) and 400
°C (750
F) to produce different microstructures. The microstructures were characterized by X-ray diffraction, scanning electron microscopy and optical metallography. A combination of exceptionally high yield strength (1336
MPa) and a high fracture of toughness of 116
MPa√m (a value comparable to maraging steel) was obtained in this steel after austempering at 316
°C (600
F) for 2
h. Potential applications of this steel include the inexpensive fabrication of armored plates and components requiring high reliability and durability.