Effect of Austempering Time on the Microstructure and Carbon Partitioning of Ultrahigh Strength Steel 56NiCrMoV7
Abstract
:1. Introduction
2. Experimental
3. Results
3.1. Hardness Property of Austempered Samples
3.2. Microstructure Observed in Optical Microscopy
3.3. Microstructure Observed in Scanning Electron Microscopy
3.4. Results of X-ray Diffraction Analyses
4. Discussion
4.1. Hardening Mechanism in Austempering Treatment
4.2. Effect of Austempering Time on the Resultant Microstructure
5. Conclusions
- (1)
- Soaking super-cooled austenite at a temperature above its Ms temperature favours the refining of the transformed ferritic microstructure, which may be related to short-range spinodal decomposition of carbon in the incubation period;
- (2)
- The best hardening state is obtained prior to remarkable carbide precipitation, i.e., when most carbon atoms remain supersaturated in the bct-structured ferrite;
- (3)
- Following longer austempering time, the bainitic ferrite becomes increasingly decarbonised through continuous carbon clustering and carbide precipitation.
Acknowledgments
Author Contributions
Conflicts of Interest
References
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Luo, Q.; Kitchen, M.; Abubakri, S. Effect of Austempering Time on the Microstructure and Carbon Partitioning of Ultrahigh Strength Steel 56NiCrMoV7. Metals 2017, 7, 258. https://doi.org/10.3390/met7070258
Luo Q, Kitchen M, Abubakri S. Effect of Austempering Time on the Microstructure and Carbon Partitioning of Ultrahigh Strength Steel 56NiCrMoV7. Metals. 2017; 7(7):258. https://doi.org/10.3390/met7070258
Chicago/Turabian StyleLuo, Quanshun, Matthew Kitchen, and Shahriar Abubakri. 2017. "Effect of Austempering Time on the Microstructure and Carbon Partitioning of Ultrahigh Strength Steel 56NiCrMoV7" Metals 7, no. 7: 258. https://doi.org/10.3390/met7070258