Mechanisms for improving tensile properties at elevated temperature in fire-resistant steel with Mo and Nb

Jo, Hyo-Haeng; Shin, Changsoo; Moon, Joonoh; Jang, Jae Hoon; Ha, Heung Yong; Park, Seongjun; Lee, Tae‐Ho; Lee, Bong Ho; Chung, Jihoon; Speer, John G.; Findley, Kip O.; Jacobs, Taylor R.; Lee, Chang‐Hoon; Kim, Sung Dae

doi:10.1016/j.matdes.2020.108882

Cited by 42 publications

(40 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…According to our results, summarized in Figure 1, it is expected that Nb could reduce almost 16 % of the vacancy formation energy compared to pure ferrite (2.23 eV), or 11 % compared to those alloys containing Mo (2.13 eV), in remarkable agreement with previous theoretical calculations [11].…”

Section: Propertiessupporting

confidence: 92%

“…Therefore, such enhancement must be imperative to the macroscopic properties of this class of steels. Furthermore, as also pointed out by Jo et al [11], the formation of solute-vacancy pairs and related lattice defects were also observed in other iron binary alloys with refractory metals [22][23][24][25], further reinforcing their importance in high-temperature resistance. Our results put a new piece in the puzzle, with B being a potentially central actor in the ongoing fire-resistant steels endeavor.…”

Section: Propertiessupporting

confidence: 67%

“…Also an important ingredient for the strength of steels, the hindering of dislocation mobility is highly desirable to improve the mechanical properties at elevated temperatures since it mitigates the dislocation annihilation with increasing temperature. Recently, Jo et al [11] proposed that the addition of transition metal solutes, especially Mo and Nb elements, significantly lowers the vacancy formation energy in Fe-BCC, paving the way for these lattice defects to be easily formed. Notably, the predicted fraction of vacancy-related defects was indeed confirmed through positron annihilation lifetime spectroscopy by the same authors [11].…”

Section: Propertiesmentioning

confidence: 99%

“…Recently, Jo et al [11] proposed that the addition of transition metal solutes, especially Mo and Nb elements, significantly lowers the vacancy formation energy in Fe-BCC, paving the way for these lattice defects to be easily formed. Notably, the predicted fraction of vacancy-related defects was indeed confirmed through positron annihilation lifetime spectroscopy by the same authors [11]. These observations led us to search for novel solute combinations through first-principles electronic-structure calculations 1 , aiming to optimize this mechanism.…”

Section: Propertiesmentioning

confidence: 99%

See 3 more Smart Citations

Synergism between B and Nb improves fire resistance in microalloyed steels

Ferreira¹,

Carvalho²,

Ariza-Echeverri³

et al. 2022

Preprint

View full text Add to dashboard Cite

The development of new fire-resistant steels represents a challenge in materials science and engineering of utmost importance. Alloying elements such as Nb and Mo are generally used to improve the strength at both room-and high-temperatures due to, for example, the formation of precipitates and harder microconstituents. In this study we show alternatively that the addition of small amounts of boron in Nb-microalloyed steels may play a crucial role in maintaining the mechanical properties at high temperatures. The 66 % yield-strength criteria for fire resistance is achieved at ≈ 574 °C for a boron steel, whereas without boron this value reaches ≈ 460 °C, a remarkable boron-induced mechanical strengthening enhancement. DFT calculations show that boron additions can lower the vacancy formation energy when compared to pure ferrite and, for Nb-B steels, there is a further 24 % reduction, suggesting that the boron-niobium combination acts as an effective pinning-based strengthening agent.

show abstract

Section: Propertiessupporting

confidence: 92%

Section: Propertiessupporting

confidence: 67%

Section: Propertiesmentioning

confidence: 99%

Section: Propertiesmentioning

confidence: 99%

See 2 more Smart Citations

Synergism between B and Nb improves fire resistance in microalloyed steels

Ferreira¹,

Carvalho²,

Ariza-Echeverri³

et al. 2022

Preprint

View full text Add to dashboard Cite

show abstract

“…[ 1–3 ] Studies have shown that the addition of Mo not only improves precipitation strengthening and solid‐solution strengthening of steel at elevated temperatures but also promotes bainitic transformation [ 1,2 ] and hinders the dislocation movement. [ 6 ] When the volume fraction of bainite exceeds ≈15%, the fire resistance is significantly improved. [ 2 ] It has also been shown that the fire resistance of bainite with high boundary density is relatively more superior than ferrite with low boundary density.…”

Section: Introductionmentioning

confidence: 99%

Effect of Microstructures on the Mechanical Behavior of Fire‐Resistant Dual‐Phase Steels at Elevated Temperature

Cong

Zhao

et al. 2021

steel research int.

View full text Add to dashboard Cite

Herein, the start laminar cooling temperature to obtain different volume fractions of ferrite and bainite/martensite is optimized. Lower start laminar cooling temperature yields a higher volume fraction of ferrite and also decreases the transformation temperature of bainite/martensite. The yield strength of the experimental dual‐phase steel at 600 °C increases from ≈484.8 to ≈526.2 MPa by decreasing the start laminar cooling temperature from 650 to 600 °C. To understand the effect of microstructure, the dislocation density, volume fraction of precipitates, and Young's modulus at elevated temperature are statistically analyzed. A machine learning method, known as gradient boosting decision tree, is used to classify the grain boundaries. The statistical results suggest that the steel subject to lower start laminar cooling temperature shows higher Young's modulus and larger volume fraction of precipitates at elevated temperature. Furthermore, at elevated temperature, the boundary is stable and the proportion of Σ3 boundary is greater, when lower start laminar cooling temperature is adopted. Theoretical calculations results suggest that the lower transformation temperature of bainite/martensite improves the fire resistance of dual‐phase steels.

show abstract

Mechanical Properties and Precipitation Behaviors of a Low‐Mo Nb–V–Ti Complex Microalloyed Fire‐Resistant Steel with Two Kinds of Microstructure

Li¹,

Zhang²,

Wang³

et al. 2021

steel research int.

View full text Add to dashboard Cite

A new type of low‐Mo Nb–V–Ti complex microalloyed fire‐resistant steel is designed. Two kinds of controlled rolling and controlled cooling processes are employed to obtain the two steels with predominantly composed of fine‐grained proeutectoid ferrite (1#) and coarse‐grained full bainite (2#), respectively. The microstructures and precipitates of the experimental steels in room temperature and 600 oC are characterized by means of the scanning electron microscope (SEM), electron backscattered diffraction (EBSD), transmission electron microscope (TEM), and physicochemical phase analysis, and the strengthening mechanisms at room temperature and elevated temperature are quantitatively calculated and analyzed. The results show that the mechanical properties of the two steels are close to each other at room temperature. However, the fire resistance of bainite steel is much better than that of ferrite steel. Nanosized M(C, N) further precipitates from bainite at elevated temperature, which improves the stability of the bainitic structure and compensates for the loss of yield strength caused by the shear modulus decreased at high temperature. The grain refinement strengthening may not play a role at 600 oC in proeutectoid ferrite steel.

show abstract

Mechanisms for improving tensile properties at elevated temperature in fire-resistant steel with Mo and Nb

Cited by 42 publications

References 23 publications

Synergism between B and Nb improves fire resistance in microalloyed steels

Synergism between B and Nb improves fire resistance in microalloyed steels

Effect of Microstructures on the Mechanical Behavior of Fire‐Resistant Dual‐Phase Steels at Elevated Temperature

Mechanical Properties and Precipitation Behaviors of a Low‐Mo Nb–V–Ti Complex Microalloyed Fire‐Resistant Steel with Two Kinds of Microstructure

Contact Info

Product

Resources

About