Thermal decomposition characteristics of retained austenite and its influence on impact toughness of B-containing 9Cr1Mo1Co(FB2) steel during the two-step tempering
The decomposition kinetics of retained austensite (RA) and the effect of its decomposition on the impact toughness of FB2 steel during the two-step tempering were studied by employing differential scanning calorimetry (DSC), magnetic saturation measurement (MSM) and transmission electron microscopy...
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| Language: | English |
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Elsevier
2021-05-01
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| Series: | Journal of Materials Research and Technology |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S223878542100332X |
| _version_ | 1818915523720642560 |
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| author | Yongqiang Zhang Jianfeng Gu Lizhan Han Gang Shen Chuanwei Li |
| author_facet | Yongqiang Zhang Jianfeng Gu Lizhan Han Gang Shen Chuanwei Li |
| author_sort | Yongqiang Zhang |
| collection | DOAJ |
| description | The decomposition kinetics of retained austensite (RA) and the effect of its decomposition on the impact toughness of FB2 steel during the two-step tempering were studied by employing differential scanning calorimetry (DSC), magnetic saturation measurement (MSM) and transmission electron microscopy (TEM). Furnace-cooling from 1100 °C produces 9.7vol.% filmy RA due to the contributions to Ms from the C enrichment (MS(Che) = 102 °C) and the high internal stress (ΔMS(stress) = -93.3 °C). With the increase of the first step tempering temperature from 570 °C to 630 °C for 1–10 h, RA involves into the different decomposition characteristics, forming θ phase, M3C particles, filmy M3C and M7C3, and also leading to the volume fraction of the carbon-depleted RA transformed into martensite fγRA→M decrease from 87.6% to 0.0% during the subsequent cooling process. During the second step tempering at 670 °C, these θ and M3C particles evolve into spherical M23C6, while film-like M3C and M7C3 evolve into filmy M23(C,B)6. Deteriorated by the filmy M23(C,B)6, the impact toughness increase from 72 J/cm2 to 118 J/cm2 with the increase of fγRA→M from 0% to 87.6%. While for the samples with fγRA→M=0, enhancing the second step tempering temperature to 690 °C for 10 h can further promote the spheroidization of filmy M23(C,B)6 and reduce hardness, resulting in the enhancement of impact toughness from 72 J/cm2 to 112 J/cm2. In summary, a two-step tempering process (570 °C for 1–5 h plus 670–690 °C for 10 h) for RA-containing FB2 steel is suggested to obtain excellent impact toughness and high hardness. |
| first_indexed | 2024-12-20T00:03:38Z |
| format | Article |
| id | doaj.art-401aed0f381a49d2ae0b854cb33d82fc |
| institution | Directory Open Access Journal |
| issn | 2238-7854 |
| language | English |
| last_indexed | 2024-12-20T00:03:38Z |
| publishDate | 2021-05-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Journal of Materials Research and Technology |
| spelling | doaj.art-401aed0f381a49d2ae0b854cb33d82fc2022-12-21T20:00:44ZengElsevierJournal of Materials Research and Technology2238-78542021-05-011224622475Thermal decomposition characteristics of retained austenite and its influence on impact toughness of B-containing 9Cr1Mo1Co(FB2) steel during the two-step temperingYongqiang Zhang0Jianfeng Gu1Lizhan Han2Gang Shen3Chuanwei Li4Institute of Materials Modification and Modelling, Shanghai Jiao Tong University, Shanghai, 200240, ChinaInstitute of Materials Modification and Modelling, Shanghai Jiao Tong University, Shanghai, 200240, China; Corresponding author.Institute of Materials Modification and Modelling, Shanghai Jiao Tong University, Shanghai, 200240, ChinaInstitute of Materials Modification and Modelling, Shanghai Jiao Tong University, Shanghai, 200240, China; School of Mechanical Engineering, Suzhou University of Science and Technology, Suzhou, Jiangsu, 215009, ChinaInstitute of Materials Modification and Modelling, Shanghai Jiao Tong University, Shanghai, 200240, ChinaThe decomposition kinetics of retained austensite (RA) and the effect of its decomposition on the impact toughness of FB2 steel during the two-step tempering were studied by employing differential scanning calorimetry (DSC), magnetic saturation measurement (MSM) and transmission electron microscopy (TEM). Furnace-cooling from 1100 °C produces 9.7vol.% filmy RA due to the contributions to Ms from the C enrichment (MS(Che) = 102 °C) and the high internal stress (ΔMS(stress) = -93.3 °C). With the increase of the first step tempering temperature from 570 °C to 630 °C for 1–10 h, RA involves into the different decomposition characteristics, forming θ phase, M3C particles, filmy M3C and M7C3, and also leading to the volume fraction of the carbon-depleted RA transformed into martensite fγRA→M decrease from 87.6% to 0.0% during the subsequent cooling process. During the second step tempering at 670 °C, these θ and M3C particles evolve into spherical M23C6, while film-like M3C and M7C3 evolve into filmy M23(C,B)6. Deteriorated by the filmy M23(C,B)6, the impact toughness increase from 72 J/cm2 to 118 J/cm2 with the increase of fγRA→M from 0% to 87.6%. While for the samples with fγRA→M=0, enhancing the second step tempering temperature to 690 °C for 10 h can further promote the spheroidization of filmy M23(C,B)6 and reduce hardness, resulting in the enhancement of impact toughness from 72 J/cm2 to 112 J/cm2. In summary, a two-step tempering process (570 °C for 1–5 h plus 670–690 °C for 10 h) for RA-containing FB2 steel is suggested to obtain excellent impact toughness and high hardness.http://www.sciencedirect.com/science/article/pii/S223878542100332XRetained austeniteDecomposition characteristicsMechanical propertiesTwo-step tempering |
| spellingShingle | Yongqiang Zhang Jianfeng Gu Lizhan Han Gang Shen Chuanwei Li Thermal decomposition characteristics of retained austenite and its influence on impact toughness of B-containing 9Cr1Mo1Co(FB2) steel during the two-step tempering Journal of Materials Research and Technology Retained austenite Decomposition characteristics Mechanical properties Two-step tempering |
| title | Thermal decomposition characteristics of retained austenite and its influence on impact toughness of B-containing 9Cr1Mo1Co(FB2) steel during the two-step tempering |
| title_full | Thermal decomposition characteristics of retained austenite and its influence on impact toughness of B-containing 9Cr1Mo1Co(FB2) steel during the two-step tempering |
| title_fullStr | Thermal decomposition characteristics of retained austenite and its influence on impact toughness of B-containing 9Cr1Mo1Co(FB2) steel during the two-step tempering |
| title_full_unstemmed | Thermal decomposition characteristics of retained austenite and its influence on impact toughness of B-containing 9Cr1Mo1Co(FB2) steel during the two-step tempering |
| title_short | Thermal decomposition characteristics of retained austenite and its influence on impact toughness of B-containing 9Cr1Mo1Co(FB2) steel during the two-step tempering |
| title_sort | thermal decomposition characteristics of retained austenite and its influence on impact toughness of b containing 9cr1mo1co fb2 steel during the two step tempering |
| topic | Retained austenite Decomposition characteristics Mechanical properties Two-step tempering |
| url | http://www.sciencedirect.com/science/article/pii/S223878542100332X |
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