Metallurgical and Materials Transactions A

, Volume 32, Issue 9, pp 2207–2217 | Cite as

Influence of martensite content and morphology on the toughness and fatigue behavior of high-martensite dual-phase steels

  • Asim Bag
  • K. K. Ray
  • E. S. Dwarakadasa
Article

Abstract

A series of high-martensite dual-phase (HMDP) steels exhibiting a 0.3 to 0.8 volume fraction of martensite (V m ), produced by intermediate quenching (IQ) of a vanadium and boron-containing microalloyed steel, have been studied for toughness and fatigue behavior to supplement the contents of a recent report by the present authors on the unusual tensile behavior of these steels. The studies included assessment of the quasi-static and dynamic fracture toughness and fatigue-crack growth (FCG) behavior of the developed steels. The experimental results show that the quasi-static fracturetoughness (K ICV ) increases with increasing V m in the range between V m =0.3 and 0.6 and then decreases, whereas the dynamic fracture-toughness parameters (K ID , K D , and J ID ) exhibit a significant increase in their magnitudes for steels containing 0.45 to 0.60 V m before achieving a saturation plateau. Both the quasi-static and dynamic fracture-toughness values exhibit the best range of toughnesses for specimens containing approximately equal amounts of precipitate-free ferrite and martensite in a refined microstructural state. The magnitudes of the fatigue threshold in HMDP steels, for V m between 0.55 and 0.60, appear to be superior to those of structural steels of a similar strength level. The Paris-law exponents (m) for the developed HMDP steels increase with increasing V m , with an attendant decrease in the pre-exponential factor (C).

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Copyright information

© ASM International & TMS-The Minerals, Metals and Materials Society 2001

Authors and Affiliations

  • Asim Bag
    • 1
  • K. K. Ray
    • 2
  • E. S. Dwarakadasa
    • 3
  1. 1.Materials and Corrosion Assessment and Testing, Det Norske Veritas Pte Ltd.DNV Technology CentreSingapore
  2. 2.the Department of Metallurgical and Materials EngineeringIndian Institute of TechnologyKharagpurIndia
  3. 3.the Department of MetallurgyIndian Institute of ScienceBangaloreIndia

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