Fatigue crack propagation in a dual-phase plain-carbon steel

Journal Article · Sat Jun 01 00:00:00 EDT 1985 · Scr. Metall.; (United States)

DOI:https://doi.org/10.1016/0036-9748(85)90039-0· OSTI ID:6394683

Tzou, J L; Ritchie, R O

The need for economical higher strength steels with good formability has led to the development in recent years of a class of low carbon steels with duplex ferrite-martensite, or dual-phase, microstructures. Such steels, which do not require extensive alloying to attain their desired properties, can be produced with a wide variety of strength and ductility combinations simply by intercritical heat treatment, involving quenching from the two-phase (..cap alpha.. + ..gamma..) field. The principle behind this is analogous to that of a composite, in that the strengthening is due primarily to the load carrying capacity of the martensite, which is located within the softer ferrite matrix which provides for ductility. The objective of this note is to demonstrate that the same concept can be applied to achieve even greater resistance to fatigue crack propagation in common mild steels. By developing a coarse duplex ferritic/martensitic microstructure to promote crack deviation and closure in AISI 1008 steel, we show that fatigue thresholds exceeding 20 MP a square root of m can be obtained, representing roughly a 50% increase over conventionally heat-treated mild steels at the same strength level.

• Research Organization: Materials and Molecular Research Division, Lawrence Berkeley Laboratory, and Department of Materials Science and Mineral Engineering, University of California, Berkeley, CA
• OSTI ID: 6394683
• Journal Information: Scr. Metall.; (United States), Journal Name: Scr. Metall.; (United States) Vol. 19:6; ISSN SCRMB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102 -- Metals & Alloys-- Structure & Phase Studies
360103* -- Metals & Alloys-- Mechanical Properties
ALLOYS
ANNEALING
CARBON ADDITIONS
CARBON STEELS
CRACK PROPAGATION
CRYSTAL GROWTH
CRYSTAL STRUCTURE
DUCTILITY
FATIGUE
FERRITE
FRACTURE MECHANICS
HEAT TREATMENTS
IRON ALLOYS
IRON BASE ALLOYS
MARTENSITE
MECHANICAL PROPERTIES
MECHANICS
MICROSTRUCTURE
STEELS
TENSILE PROPERTIES
THERMAL FATIGUE
YIELD STRENGTH