IMPACT TOUGHNESS OP AUSTEMPERED DUCTILE CAST IRON

Abu-Elfotouh, H.; Abu-Zeid, O. A.; Elsarnagawy, B. A.; Eleiche, A. M.

doi:10.21608/amme.1986.57076

IMPACT TOUGHNESS OP AUSTEMPERED DUCTILE CAST IRON

Document Type : Original Article

Authors

¹ Dept. of Metallurgy,Military Technical College,Cairo,Egypt.

² Dept. of Mech. Design and Prod.,Cairo University,Egypt.

³ On leave to Dept. of Engineering,The American University in Cairo, Egypt.

10.21608/amme.1986.57076

Abstract

The influence of austempering temperature and time, as main austempering control parameters, on the impact toughness and microstructure of a ductile cast iron alloy having a carbon equivalent of 3.88 percent has been investigated. Two transformation temperatures were chosen at 270°C and 400°C such as to obtain microstructure falling within the zones of lower and upper bainite, respectively. Austempering time intervals ranging from 5 minutes to 5 hours were selected for each austempering temperature. Peak values of U-notch Charpy impact toughness of 7.55 and 17.23 Joule/cm² have been attained at time interval of 60 minutes for specimens austempered at 270°C and 400°C, respectively. The changes in mechanical properties with the transformation temperature and time has been observed to be directly related to the phase transformations in the micro-structure. The study of fracture surfaces of impact toughness samples revealed the great complexity of the crack propagation process in austempered ductile iron due to the nature of its structure.

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