The effect of phase continuity on the fatigue and crack closure behavior of a dual-phase steel
The effect of phase continuity on the low cycle fatigue and fatigue crack growth behavior of a Fe-C-Mn dual-phase steel has been investigated. Two microstructures, one consisting of continuous ferrite and the other continuous martensite, were examined. Although there was no difference in the low cycle fatigue lives between the two microstructures, the continuous martensite structure exhibited an extremely high fatigue threshold value of 20 MPa m/sup 1/2/, compared to 16 MPa m/sup 1/2/ for the continuous ferrite microstructure. A major effect of phase continuity has also been found in the crack closure levels during fatigue crack propagation studied over three decades of crack growth rates. The continuous martensite microstructure exhibited much higher closure levels due to the martensite constraining the plastic deformation in the ferrite and bearing a larger portion of the applied cyclic load. This effect is similar to the extrinsic toughening phenomenon cited in the literature. After accounting for the closure levels the intrinsic or effective fatigue crack growth rates are similar for the two microstructures. These intrinsic thresholds are predicted by employing experimentally obtained low cycle fatigue parameters and the ferrite grain size.
- Research Organization:
- Dept. of Materials Science, Univ. of Virginia, Thornton Hall, Charlottesville, VA (US)
- OSTI ID:
- 7079624
- Journal Information:
- Metall. Trans., A; (United States), Journal Name: Metall. Trans., A; (United States) Vol. 18A:7; ISSN MTTAB
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360102 -- Metals & Alloys-- Structure & Phase Studies
360103* -- Metals & Alloys-- Mechanical Properties
ALLOYS
CARBON ADDITIONS
CRACK PROPAGATION
CRYSTAL STRUCTURE
DYNAMIC LOADS
FATIGUE
FERRITIC STEELS
FRACTURE MECHANICS
FRACTURE PROPERTIES
GRAIN SIZE
IRON ALLOYS
IRON BASE ALLOYS
MARTENSITE
MECHANICAL PROPERTIES
MECHANICS
MICROSTRUCTURE
PLASTICITY
SIZE
STEELS
STRUCTURAL CHEMICAL ANALYSIS
THERMAL FATIGUE