Abstract
Formable ultra high-strength TRIP-aided steel with bainitic ferrite matrix structure (TBF
steel) contributes to a drastic weight reduction and an improvement of crash safety of automobile.
In this study, fatigue strength of 0.2%C-1.5%Si-1.5%Mn TBF steels was investigated. High fatigue
limit was achieved in TBF steels austempered at 400-450oC, containing a large amount of stable
retained austenite. The fatigue limit was linearly related with mobile dislocation density, as well as
TRIP effect of retained austenite. When compared to conventional martensitic steel, the TBF steel
exhibited lower notch-sensitivity or higher notched fatigue performance. Complex additions of
0.5%Al, 0.05%Nb and 0.2%Mo considerably improved the notched fatigue performance, as well as
the smooth fatigue strength. This was associated with the stabilized retained austenite and refined
microstructure which suppress fatigue crack initiation and/or propagation.
Publisher
Trans Tech Publications, Ltd.
Subject
Mechanical Engineering,Mechanics of Materials,General Materials Science
Cited by
6 articles.
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