Metallurgical and Materials Transactions A

, Volume 32, Issue 9, pp 2207–2217

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

Authors

  • Asim Bag
    • Materials and Corrosion Assessment and Testing, Det Norske Veritas Pte Ltd.DNV Technology Centre
  • K. K. Ray
    • the Department of Metallurgical and Materials EngineeringIndian Institute of Technology
  • E. S. Dwarakadasa
    • the Department of MetallurgyIndian Institute of Science
Article

DOI: 10.1007/s11661-001-0196-5

Cite this article as:
Bag, A., Ray, K.K. & Dwarakadasa, E.S. Metall and Mat Trans A (2001) 32: 2207. doi:10.1007/s11661-001-0196-5

Abstract

A series of high-martensite dual-phase (HMDP) steels exhibiting a 0.3 to 0.8 volume fraction of martensite (Vm), 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 (KICV) increases with increasing Vm in the range between Vm=0.3 and 0.6 and then decreases, whereas the dynamic fracture-toughness parameters (KID, KD, and JID) exhibit a significant increase in their magnitudes for steels containing 0.45 to 0.60 Vm 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 Vm 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 Vm, with an attendant decrease in the pre-exponential factor (C).

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