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The tempering behavior of martensite/austenite islands on the mechanical properties of a low alloy Mn-Ni-Mo steel with granular bainite

Authors :
Yiyi Li
Dianzhong Li
Zhen-Dan Yang
Pei Wang
Yong-Han Li
Jiang Zhonghua
Source :
Materials Today Communications. 26:102166
Publication Year :
2021
Publisher :
Elsevier BV, 2021.

Abstract

The effects of tempering on the microstructure and mechanical properties of a low alloy Mn-Ni-Mo steel were investigated. The results indicate that the steel is characterized by granular bainite consisting of bainitic ferrite, blocky islands of martensite and/or austenite (M-A islands) and film-type retained austenite (AR) before tempering. The volume fraction of AR decreases with an increase in the tempering temperature: slowly before 280°C, rapidly at 350°C, and approaching zero at 450°C. When tempered at 280°C, the steel has optimum mechanical properties because of the internal stress relaxation and the decomposition of blocky M-A islands, especially twinned martensite islands. Additionally, the enhancement of AR stability is to some extent responsible for improving the impact toughness. When tempered at 350−450°C, tempering brittleness occurs, which results from the decomposition of the AR films into discrete flake-type carbides along the interfaces. Further increase in the tempering temperature results in high toughness and low strength of the steel, mainly due to the recovery and recrystallization of bainitic ferrite, and the precipitation of globular M3C carbides.

Details

ISSN :
23524928
Volume :
26
Database :
OpenAIRE
Journal :
Materials Today Communications
Accession number :
edsair.doi...........6a6debb51585b836751e5850efb33a1c