Low-carbon cast microalloyed steel intercritically heat-treated at different temperatures: microstructure and mechanical properties
| Autor: | David San-Martin, Yahya Palizdar, Javier Vivas, Shahram Raygan, Carlos García Mateo, H. Torkamani, J. Rassizadehghani |
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| Přispěvatelé: | Ministerio de Economía y Competitividad (España), Luleå University of Technology |
| Rok vydání: | 2021 |
| Předmět: |
Austenite
Quenching Yield (engineering) Materials science 020502 materials Mechanical Engineering Mechanical properties 02 engineering and technology engineering.material 021001 nanoscience & nanotechnology Cast low-carbon steel Indentation hardness 0205 materials engineering Ferrite (iron) Martensite Ultimate tensile strength engineering Microalloyed steel Composite material Dual-phase structure 0210 nano-technology Intercritical heat treatment Civil and Structural Engineering |
| Zdroj: | Digital.CSIC. Repositorio Institucional del CSIC instname |
| Popis: | In this study, dual-phase (DP, ferrite + martensite) microstructures were obtained by performing intercritical heat treatments (IHT) at 750 and 800 °C followed by quenching. Decreasing the IHT temperature from 800 to 750 °C leads to: (i) a decrease in the volume fraction of austenite (martensite after quenching) from 0.68 to 0.36; (ii) ~ 100 °C decrease in martensite start temperature (Ms), mainly due to the higher carbon content of austenite and its smaller grains at 750 °C; (iii) a reduction in the block size of martensite from 1.9 to 1.2 μm as measured by EBSD. Having a higher carbon content and a finer block size, the localized microhardness of martensite islands increases from 380 HV (800 °C) to 504 HV (750 °C). Moreover, despite the different volume fractions of martensite obtained in DP microstructures, the hardness of the steels remained unchanged by changing the IHT temperature (~ 234 to 238 HV). Applying lower IHT temperature (lower fraction of martensite), the impact energy even decreased from 12 to 9 J due to the brittleness of the martensite phase. The results of the tensile tests indicate that by increasing the IHT temperature, the yield and ultimate tensile strengths of the DP steel increase from 493 to 770 MPa, and from 908 to 1080 MPa, respectively, while the total elongation decreases from 9.8 to 4.5%. In contrast to the normalized sample, formation of martensite in the DP steels could eliminate the yield point phenomenon in the tensile curves, as it generates free dislocations in adjacent ferrite. The authors are grateful to the Phase Transformations and Microscopy labs from CENIM-CSIC. Mr. Javier Vara Miñambres from the Phase Transformations lab (CENIM-CSIC) is gratefully acknowledged for his continuous experimental support. J. Vivas acknowledges financial support in the form of a FPI Grant BES-2014-069863 from the Ministerio de Economia y Competitividad (MINECO). Open access funding provided by Lulea University of Technology. |
| Databáze: | OpenAIRE |
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