Impact Toughness of Subzones in the Intercritical Heat-Affected Zone of Low-Carbon Bainitic Steel
The subzones of the intercritical heat-affected zone (IC HAZ) of low-carbon bainitic steel were simulated by using a Gleeble-3500 simulator to study the impact toughness. The results showed that the IC HAZ is not entirely brittle and can be further divided into three subzones according to the impact...
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MDPI AG
2018-06-01
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| Online Access: | http://www.mdpi.com/1996-1944/11/6/959 |
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| author | Zhenshun Li Xuemin Zhao Dongri Shan |
| author_facet | Zhenshun Li Xuemin Zhao Dongri Shan |
| author_sort | Zhenshun Li |
| collection | DOAJ |
| description | The subzones of the intercritical heat-affected zone (IC HAZ) of low-carbon bainitic steel were simulated by using a Gleeble-3500 simulator to study the impact toughness. The results showed that the IC HAZ is not entirely brittle and can be further divided into three subzones according to the impact toughness or peak welding temperature; the invariant subzone heated between the critical transformation start temperature (Ac1) and 770 °C exhibited unchanged high impact toughness. Furthermore, an extremely low impact toughness was found in the embrittlement subzone, heated between 770 and 830 °C, and the reduction subzone heated between 830 °C and the critical transformation finish temperature (Ac3) exhibited toughness below that of the original metal. The size of the blocky martensite-austenite (M-A) constituents was found to have a remarkable level of influence on the impact toughness when heated below 830 °C. Additionally, it was found that, once the constituent size exceeds a critical value of 3.0 µm at a peak temperature of 770 °C, the IC HAZ becomes brittle regardless of lath or twinned martensite constitution in the M-A constituent. Essentially, embrittlement was observed to occur when the resolved length of initial cracks (in the direction of the overall fracture) formed as a result of the debonding of M-A constituents exceeding the critical Griffith size. Furthermore, when the heating temperature exceeded 830 °C, the M-A constituents formed a slender shape, and the impact toughness increased as the area fraction of the slender M-A constituents decreased. |
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| id | doaj.art-e572ae6d38fb4874800bcfea04a0abe2 |
| institution | Directory Open Access Journal |
| issn | 1996-1944 |
| language | English |
| last_indexed | 2024-04-13T04:31:51Z |
| publishDate | 2018-06-01 |
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| spelling | doaj.art-e572ae6d38fb4874800bcfea04a0abe22022-12-22T03:02:18ZengMDPI AGMaterials1996-19442018-06-0111695910.3390/ma11060959ma11060959Impact Toughness of Subzones in the Intercritical Heat-Affected Zone of Low-Carbon Bainitic SteelZhenshun Li0Xuemin Zhao1Dongri Shan2Engineering Training Center, Qilu University of Technology (Shandong Academy of Sciences), Jinan 250353, ChinaEngineering Training Center, Qilu University of Technology (Shandong Academy of Sciences), Jinan 250353, ChinaSchool of Mechanical and Automotive Engineering, Qilu University of Technology (Shandong Academy of Sciences), Jinan 250353, ChinaThe subzones of the intercritical heat-affected zone (IC HAZ) of low-carbon bainitic steel were simulated by using a Gleeble-3500 simulator to study the impact toughness. The results showed that the IC HAZ is not entirely brittle and can be further divided into three subzones according to the impact toughness or peak welding temperature; the invariant subzone heated between the critical transformation start temperature (Ac1) and 770 °C exhibited unchanged high impact toughness. Furthermore, an extremely low impact toughness was found in the embrittlement subzone, heated between 770 and 830 °C, and the reduction subzone heated between 830 °C and the critical transformation finish temperature (Ac3) exhibited toughness below that of the original metal. The size of the blocky martensite-austenite (M-A) constituents was found to have a remarkable level of influence on the impact toughness when heated below 830 °C. Additionally, it was found that, once the constituent size exceeds a critical value of 3.0 µm at a peak temperature of 770 °C, the IC HAZ becomes brittle regardless of lath or twinned martensite constitution in the M-A constituent. Essentially, embrittlement was observed to occur when the resolved length of initial cracks (in the direction of the overall fracture) formed as a result of the debonding of M-A constituents exceeding the critical Griffith size. Furthermore, when the heating temperature exceeded 830 °C, the M-A constituents formed a slender shape, and the impact toughness increased as the area fraction of the slender M-A constituents decreased.http://www.mdpi.com/1996-1944/11/6/959intercritical heat-affected zoneimpact toughnessmartensite-austenite constituentcritical sizelow-carbon bainitic steel |
| spellingShingle | Zhenshun Li Xuemin Zhao Dongri Shan Impact Toughness of Subzones in the Intercritical Heat-Affected Zone of Low-Carbon Bainitic Steel Materials intercritical heat-affected zone impact toughness martensite-austenite constituent critical size low-carbon bainitic steel |
| title | Impact Toughness of Subzones in the Intercritical Heat-Affected Zone of Low-Carbon Bainitic Steel |
| title_full | Impact Toughness of Subzones in the Intercritical Heat-Affected Zone of Low-Carbon Bainitic Steel |
| title_fullStr | Impact Toughness of Subzones in the Intercritical Heat-Affected Zone of Low-Carbon Bainitic Steel |
| title_full_unstemmed | Impact Toughness of Subzones in the Intercritical Heat-Affected Zone of Low-Carbon Bainitic Steel |
| title_short | Impact Toughness of Subzones in the Intercritical Heat-Affected Zone of Low-Carbon Bainitic Steel |
| title_sort | impact toughness of subzones in the intercritical heat affected zone of low carbon bainitic steel |
| topic | intercritical heat-affected zone impact toughness martensite-austenite constituent critical size low-carbon bainitic steel |
| url | http://www.mdpi.com/1996-1944/11/6/959 |
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