Influence of microstructure on fracture toughness of austempered ductile iron

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Physical metallurgy and materials science, 1997-07, Vol.28 (7), p.1457-1470
• Main Authors: PRASAD RAO, P, PUTATUNDA, S. K
• Format: Article
• Language: English
• Subjects: Applied sciences; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Fatigue, corrosion fatigue, embrittlement, cracking, fracture and failure; Fatigue, embrittlement, and fracture; Materials science; Metals. Metallurgy; Physics; Treatment of materials and its effects on microstructure and properties
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-997-0208-1

An investigation was carried out to examine the influence of microstructure on the plane strain fracture toughness of austempered ductile iron. Austempered ductile iron (ADI) alloyed with nickel, copper, and molybdenum was austenitized and subsequently austempered over a range of temperatures to produce different microstructures. The microstructures were characterized through optical microscopy and x-ray diffraction. Plane strain fracture toughness of all these materials was determined and was correlated with the microstructure. The results of the present investigation indicate that the lower bainitic microstructure results in higher fracture toughness than upper bainitic microstructure. Both volume fraction of retained austenite and its carbon content influence the fracture toughness. The retained austenite content of 25 vol.% was found to provide the optimum fracture toughness. It was further concluded that the carbon content of the retained austenite should be as high as possible to improve fracture toughness.