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Strengthening mechanisms of solid solution and precipitation at elevated temperature in fire-resistant steels and the effects of Mo and Nb addition

Title
Strengthening mechanisms of solid solution and precipitation at elevated temperature in fire-resistant steels and the effects of Mo and Nb addition
Authors
Moon, JoonohKim, Sung-DaeLee, Chang-HoonJo, Hyo-HaengHong, Hyun-UkChung, Jun-HoLee, Bong Ho
DGIST Authors
Moon, Joonoh; Kim, Sung-Dae; Lee, Chang-Hoon; Jo, Hyo-Haeng; Hong, Hyun-Uk; Chung, Jun-Ho; Lee, Bong Ho
Issue Date
2021-11
Citation
Journal of Materials Research and Technology, 15, 5095-5105
Type
Article
Author Keywords
Constant-load testDislocation annihilationFire-resistant steelHigh-temperature strengthStrengthening mechanism
Keywords
High resolution transmission electron microscopyHigh strength steelMolybdenumNiobiumNiobium compoundsPrecipitation (chemical)Solid solutionsStrengthening (metal)Titanium carbideCoarse particlesConstant load testsDislocation annihilationElevated temperatureFire resistant steelHigh temperature strengthHighest temperatureMo additionsStrengthening mechanismsTension testsTensile testingBuilding materialsCompression testingFire resistance
ISSN
2238-7854
Abstract
Fire–resistant properties of Mo-/Nb-added structural steels were evaluated using hot tension tests and constant-load tests. Hot tension tests showed that an increase in the Mo and Nb contents led to a slow decrease in the strength as the holding time increased at a high temperature (600 °C), enhancing the fire resistance. Transmission electron microscopy (TEM) and atom probe tomography analyses revealed that this improved fire resistance stemmed from the annihilation of dislocations at high temperatures, which was suppressed by the solid solution of Mo atoms and fine precipitation of Ti/Nb-enriched MC carbides. Meanwhile, an increase in Ti content decreased fire resistance via precipitation of coarse TiC particles, i.e., in-situ TEM observations showed that dislocations moved easily along the surface of coarse particles by climb, indicating that coarse particles did not play a role in disturbing dislocation movement during deformation at high temperatures. Next, constant-load tests were carried out with a constant load of 50% of the yield strength, while the temperature was increased linearly until failure. The results were in good agreement with the results of the hot tension tests; i.e., the failure temperature increased with an increase in the Mo and Nb contents, indicating improvement in fire resistance. © 2021 The Authors
URI
http://hdl.handle.net/20.500.11750/15836
DOI
10.1016/j.jmrt.2021.10.132
Publisher
Elsevier Editora Ltda
Related Researcher
Files:
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Collection:
Center for Core Research Facilities1. Journal Articles


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