Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10142054 | Materials Science and Engineering: A | 2018 | 37 Pages |
Abstract
In a 0.05C-5.4Mn-0.2Si-0.8Cr-wt% steel intercritically tempered at 700â¯Â°C for 50â¯min a new hexagonal closed-packed phase (ε-martensite) appears on former reversed austenite by an air-cooled process. The tensile strength of the tested steel increased from ~â¯840â¯MPa after intercritical tempering at 650â¯Â°C for 50â¯min to ~â¯1002â¯MPa with the tempering temperature increased to 700â¯Â°C, and the product of strength and elongation was improved from 19.9â¯GPaâ¯% to 21.6â¯GPaâ¯%; moreover, the impact energy at ââ¯40â¯Â°C was decreased from 143â¯J to 68â¯J, and the yield ratio was reduced from 0.84 to 0.50. This result was attributed to the weakening of TRIP effect in existence of ε-martensite. The partitioning of alloying elements at different intercritical tempering conditions and the calculation of SFE (stacking faults energy) indicated that ε-martensite was produced in the ~â¯50-100â¯Â°C temperature range while cooling in air after tempering at 700â¯Â°C for 50â¯min ε-Martensite affected the stability of the reversed austenite and the fracture mode. The fracture mode was changed with the increased tempering temperature. The results reveal that a multiphase low-C medium-Mn steel can be produced via intercritical tempering accompanied by a unique phase transformation process. A high-temperature and long-time tempering condition will lead to a thermally-induced ε-martensite transformation due to lower SFE possibly associated with more homogenized (or less amount of) alloying elements in austenite, and affects the mechanical behaviors of medium Mn steel.
Related Topics
Physical Sciences and Engineering
Materials Science
Materials Science (General)
Authors
Guanqiao Su, Xiuhua Gao, Ting Yan, Dazheng Zhang, Chenshuo Cui, Linxiu Du, Zhenguang Liu, Yan Tang, Jun Hu,