The influence of austempering temperature on the microstructure and mechanical properties of a high carbon high silicon steel

In this investigation a new bainitic steel with high strength and exceptionally high fracture toughness has been developed. This steel has been synthesized using the concepts from Austempered Ductile Cast Iron (ADI) technology. The influence of austempering temperature on the microstructure and mechanical properties of this steel at room temperature and ambient atmosphere has been examined. The influence of microstructure on plane strain fracture toughness of this steel was also investigated.; Compact tension and cylindrical tensile specimens prepared from the steel were initially Austenitized at 927°C for 2 hours and then subsequently austempered at several temperatures between 260°C and 400°C to produce different microstructures. The microstructures were characterized by X-ray diffraction and optical metallography; and fracture surfaces were studied using scanning electron microscope. The test results show that exceptionally high fracture of toughness of 116 MPa√m (comparable to Maraging steel) is produced in the steel after austempering at 315°C. Potential applications of this steel include armored plates and other high penetration resistance applications.