Microstructural and mechanical properties of low-carbon ultra-fine bainitic steel produced by multi-step austempering process

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:734

Article

Mousalou, Hamid¹  Yazdani, Sasan¹  Avishan, Behzad²  Ahmadi, Naghi Parvini¹  Chabok, Ali³  Pei, Yutao³ 

[1] Sahand Univ Technol, Fac Mat Engn, Tabriz, Iran

[2] Azarbaijan Shahid Madani Univ, Dept Mat Engn, Tabriz, Iran

[3] Univ Groningen, Fac Sci & Engn, Dept Adv Prod Engn, Nijenborgh 4, NL-9747 AG Groningen, Netherlands

关键词: Bainite;    Multi-step austempering;    Mechanical properties;    EBSD;    SEM;    XRD;   

DOI  :  10.1016/j.msea.2018.08.008

来源: Elsevier

【 摘 要 】

The multi-step isothermal austempering heat treatment to achieve an ultra-fine bainitic microstructure and maximum volume fraction of bainite was conducted on a steel containing 0.26 wt% carbon. The microstructural and crystallographic characteristics, as well as the mechanical properties and fracture behavior were studied. The results showed that the subsequent austempering heat treatment at a lower temperature, immediately after partial bainite formation at a higher temperature, would replace the coarse austenite/martensite areas with much refined bainite consisting nanoscale plates of bainitic ferrite and filmy austenite which ultimately leads to the refinement of the bainitic microstructure. This microstructural modification, in addition to the increased yield strength, causes a significant increase in the impact fracture toughness of the multi-step austempered steels. The EBSD analysis also showed that the subsequent austempering heat treatment at a lower temperature results in a finer structure of Bain groups and increase in the fraction of high angle grain boundaries leading to higher resistance against crack propagation and subsequently higher impact energy absorption.

【 授权许可】

Free