Effect of Heterogeneous Microstructure on Refining Austenite Grain Size in Low Alloy Heavy-Gage Plate
Abstract
:1. Introduction
2. Experimental Material and Procedure
3. Results and Discussion
3.1. Refining Prior Austenite Grain
3.2. Crystallographic Characteristics of Pre-Annealed Microstructure
3.3. Enrichment of Alloying Elements
3.4. Role of Heterogeneous Microstructure
3.5. Nucleation Rate of Reversed Austenite
4. Conclusions
- The heterogeneous microstructures of alloying elements-enriched fresh martensite and -depleted intercritical ferrite were obtained after intercritical annealing. The fresh martensite was distributed at prior austenite grain boundary (G-M) and inter-lath (L-M). G-M was transformed by equiaxed reversed austenite and the L-M was formed by acicular reversed austenite, when the reversed austenite obtained during intercritical annealing was quenched to room temperature.
- The heterogeneous microstructure increased the intrinsic energy difference of fcc phase and bcc phase below 763 °C or above 815 °C, and the interface energy decreased because of alloying element enrichment at the interface, which reduces the nucleation energy barrier according to the nucleation theory under ideal state. Therefore, the nucleation driving energy of equiaxed reversed austenite is less. The heterogeneous microstructure can enhance the equiaxed reversed austenite nucleation at intragranular and prior austenite grain boundary during reheating, which effectively refined the coarse prior austenite grains in the core of hot rolled heavy plate processed by TMCP.
- The prior austenite grains in the core of heavy plate processed by TMCP was very large (~105 μm). The austenite grains were inhomogeneous when the hot rolled specimen was reheated by one-step heat treatment process. However, for the two-step heat treatment process, fine and uniform austenite grain size (~12 μm) was obtained, which was two times finer compared to the one-step heat treatment. An effective way of improving strength, ductility and low temperature toughness in alloy steel is to refine the prior austenite grain size. This study provides a possible way of effectively refining prior austenite grain size.
Author Contributions
Funding
Conflicts of Interest
References
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Position | Mn | Ni | Cu | Cr |
---|---|---|---|---|
1# | 1.89 | 1.59 | 0.68 | 0.51 |
2# | 2.08 | 1.67 | 0.85 | 0.68 |
3# | 1.81 | 1.56 | 0.72 | 0.56 |
4# | 1.95 | 1.57 | 0.79 | 0.59 |
5# | 2.09 | 1.74 | 0.82 | 0.65 |
Mean | 1.96 | 1.63 | 0.77 | 0.60 |
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Yuan, S.; Xie, Z.; Wang, J.; Zhu, L.; Yan, L.; Shang, C.; Misra, R.D.K. Effect of Heterogeneous Microstructure on Refining Austenite Grain Size in Low Alloy Heavy-Gage Plate. Metals 2020, 10, 132. https://doi.org/10.3390/met10010132
Yuan S, Xie Z, Wang J, Zhu L, Yan L, Shang C, Misra RDK. Effect of Heterogeneous Microstructure on Refining Austenite Grain Size in Low Alloy Heavy-Gage Plate. Metals. 2020; 10(1):132. https://doi.org/10.3390/met10010132
Chicago/Turabian StyleYuan, Shengfu, Zhenjia Xie, Jingliang Wang, Longhao Zhu, Ling Yan, Chengjia Shang, and R. D. K. Misra. 2020. "Effect of Heterogeneous Microstructure on Refining Austenite Grain Size in Low Alloy Heavy-Gage Plate" Metals 10, no. 1: 132. https://doi.org/10.3390/met10010132
APA StyleYuan, S., Xie, Z., Wang, J., Zhu, L., Yan, L., Shang, C., & Misra, R. D. K. (2020). Effect of Heterogeneous Microstructure on Refining Austenite Grain Size in Low Alloy Heavy-Gage Plate. Metals, 10(1), 132. https://doi.org/10.3390/met10010132