Micromechanisms of Dynamic Crack Propagation in an AISI 4340 Steel
Abstract
The present work is aimed at understanding the micromechanisms of dynamic crack growth at room temperature and a low temperature (-100 C) in an AISI 4340 steel studied by Ravichandran and Clifton. For this purpose, a fractographic and metallographic examination of the specimens used by Ravichandran and Clifton was carried out. Results showed that the steel contained an appreciable amount of upper bainite (about 15%). The study suggests that dynamic crack propagation in the 4340 steel occurs in two stages, i.e., nucleation of microcracks in the upper bainite followed by propagation of these microcracks into the surrounding martensite. At low temperatures, failure of the martensite occurs by cleavage whereas, at room temperature, it occurs by shear localization, leading to microvoid growth and coalescence. At both temperatures, bainitic microcracks serves as failure initiation sites and reduce the dynamic fracture toughness of the steel.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1989
- Accession Number
- ADA213507
Entities
People
- G. Ravichandran
- R. Godse
- Rodney J. Clifton
Organizations
- Brown University