ON THE MICROSTRUCTURAL SENSITIVITY OF FRACTURE TOUGHNESS,
Abstract
Deformation of a metastable 0.25C-5Cr-Mo-V austenite at 405 C, or about 40 C above the M sub s temperature, produced a two-phase microstructure of bainite and martensite. This microstructure exhibited abnormally high toughness at crack-instability (4000 in. -lb/sq. in. for 240-Ksi yield strength material) and a relatively low value at the initiation of crack propagation (70 in. -lb/sq. in.). Deformation at the M sub s or more than 100 C aboce the M sub s produced a one-phase martensite structure that exhibited toughness at crack-instability that was lower by a factor of 100. The uniaxial stress-strain curves were identical for both microstructures and thus contradict current continuum mechanics fracture theories derived from uniaxial tensile behavior. This anomaly is explained in terms of a model that considers the micromechanics of crack arrest and reinitiation in a two-phase microstructure where the bainite constituent is considerably tougher than martensite.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1966
- Accession Number
- AD0486333
Entities
People
- Louis Raymond
- Walter G. Reuter
- William W. Gerberich
Organizations
- The Aerospace Corporation