Microstructure and mechanical properties of ultrahigh-strength TRIP-aided steels

Koh Ichi Sugimoto, Junya Kobayashi, Tomohiko Hojo

Research output: Contribution to journalReview articlepeer-review

14 Citations (Scopus)

Abstract

This paper introduces the microstructure, retained austenite characteristics, strain-induced transformation-deformation mechanism and mechanical properties of transformation-induced plasticity (TRIP)-aided martensitic (TM) steels for the automotive applications. Because the microstructure consists of a wide lath-martensite structured matrix and a mixture of narrow lath-martensite and metastable retained austenite (MA-like phase), the TM steel produced a good combination of tensile strength and cold formability. If Cr and/or Mo were added into 0.2%C-1.5%Si-1.5%Mn steel to enhance its hardenability, the resultant TM steel achieved superior notch fatigue strength and impact and fracture toughness to conventional structural steel such as SCM420. These enhanced mechanical properties were found to be mainly caused by: (1) plastic relaxation of the stress concentration, which results from expansion strain on the strain-induced transformation of the metastable retained austenite; and (2) the presence of a large quantity of finely dispersed MA-like phase, which suppresses crack or void initiation and subsequent connection.

Original languageEnglish
Pages (from-to)1-11
Number of pages11
JournalTetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan
Volume103
Issue number1
DOIs
Publication statusPublished - 2017
Externally publishedYes

Keywords

  • Mechanical property
  • Microstructure
  • Retained austenite
  • Strain-induced martensite transformation
  • TRIP-aided martensitic steel

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Physical and Theoretical Chemistry
  • Metals and Alloys
  • Materials Chemistry

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