Fatigue properties of nitrogen added ultra high-strength low alloy, TRIP-aided steels

Tomohiko Hojo, Junya Kobayashi, Koh Ichi Sugimoto

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

To develop ultra high-strength steels for automotive impact safety parts and forging parts, the fatigue properties of ultra high-strength low alloy TRIP-aided steels with martensite (TM), bainitic ferrite (TBF) and martensite-bainite (TBM) matrix were investigated. TM steels achieved both high tensile strength of 1370 MPa grade and excellent fatigue properties compared with TBF and TBM steels. This was caused by the suppression of crack initiations and propagations due to the effective transformation induced plasticity of retained austenite because of the existence of fine marteniste lath matrix and interlath retained austenite. TM and TBM steels indicated excellent fatigue properties compared with TBF steels. This was caused by the fine and uniform lath matrix and interlath retained austenite and increased tensile strength and yield strength due to the austempering treatment at low tempertature. Fatigue properties of ultra high-strength low alloy TRIP-aided steels were increased by the addition of nitrogen. Particularly, the nitrogen addition of 100 ppm improved fatigue properties. This suggested that initiation and propagation of cracks were suppressed by the effective strain induced plasticity of fine and stable retained austenite.

Original languageEnglish
Title of host publicationMaterials Science and Technology Conference and Exhibition 2013, MS and T 2013
Pages169-176
Number of pages8
Publication statusPublished - 2013 Dec 1
Externally publishedYes
EventMaterials Science and Technology Conference and Exhibition 2013, MS and T 2013 - Montreal, QC, Canada
Duration: 2013 Oct 272013 Oct 31

Publication series

NameMaterials Science and Technology Conference and Exhibition 2013, MS and T 2013
Volume1

Other

OtherMaterials Science and Technology Conference and Exhibition 2013, MS and T 2013
CountryCanada
CityMontreal, QC
Period13/10/2713/10/31

Keywords

  • Fatigue properties
  • Nitrogen
  • Retained austenite
  • TRIP
  • Ultra high strength steel

ASJC Scopus subject areas

  • Mechanics of Materials

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  • Cite this

    Hojo, T., Kobayashi, J., & Sugimoto, K. I. (2013). Fatigue properties of nitrogen added ultra high-strength low alloy, TRIP-aided steels. In Materials Science and Technology Conference and Exhibition 2013, MS and T 2013 (pp. 169-176). (Materials Science and Technology Conference and Exhibition 2013, MS and T 2013; Vol. 1).