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Microstructural evolution of bainitic steel severely deformed by equal channel angular pressing
M Nili-Ahmadabadi1, F Haji Akbari, F Rad
1School of Metallurgy and Materials Engineering, Faculty of Engineering, University of Tehran, P.O. Box: 14395-731, Tehran, Iran.
Journal of Nanoscience and Nanotechnology
|December 8, 2010
Summary
Severe plastic deformation using Equal Channel Angular Pressing transforms retained austenite to martensite in high silicon bainitic steel. This transformation enhances the steel
Area of Science:
- Materials Science
- Metallurgy
- Mechanical Engineering
Background:
- High silicon bainitic steel offers a unique combination of ultra-high strength, good ductility, and wear resistance.
- This steel grade is of significant interest for applications requiring robust mechanical performance.
- Understanding its behavior under extreme deformation is crucial for optimizing its properties.
Purpose of the Study:
- To investigate the impact of severe plastic deformation on the microstructure and properties of high silicon bainitic steel.
- To analyze the role of retained austenite during plastic deformation.
- To correlate microstructural changes with mechanical property enhancements.
Main Methods:
- Utilized a high Si bainitic steel (Fe-0.22C-2.0Si-3.0Mn) with a microstructure suitable for severe plastic deformation.
- Applied Equal Channel Angular Pressing (ECAP) for two passes at room temperature to induce severe plastic deformation.
- Employed optical, Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM) for microstructural examination.
- Used X-ray diffraction (XRD) to quantify retained austenite levels before and after ECAP.
Main Results:
- Microstructural analysis revealed significant changes after ECAP processing.
- X-ray diffraction indicated the disappearance of retained austenite peaks post-ECAP.
- The transformation of retained austenite to martensite during severe plastic deformation was observed.
- A notable enhancement in hardness values was recorded with increasing ECAP passes.
Conclusions:
- Severe plastic deformation via ECAP effectively modifies the microstructure of high Si bainitic steel.
- The transformation of retained austenite to martensite during ECAP is a key mechanism for property enhancement.
- ECAP processing offers a viable route to further improve the strength and hardness of this advanced bainitic steel.
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