Atomic-scale study on segregation behavior at austenite grain boundaries in boron- and molybdenum-added steels

“…The effect of the Cottrell atmosphere around boundaries may be responsible for this change. Carbon atoms segregate around boundaries and dislocations to reduce distortion energy, leading to the formation of the Cottrell atmosphere [36][37][38]. During the slipping process, the dislocations are forced to move along with the Cottrell atmospheres, resulting in the so-called "drag effect", which can effectively increase the resistance of the dislocation movement and pin the dislocation.…”

Section: Effect Of Carbon Content On the Effective Grain Size Of Strementioning

confidence: 99%

The Effect of Lath Martensite Microstructures on the Strength of Medium-Carbon Low-Alloy Steel

Sun

Liu

et al. 2020

Crystals

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Different austenitizing temperatures were used to obtain medium-carbon low-alloy (MCLA) martensitic steels with different lath martensite microstructures. The hierarchical microstructures of lath martensite were investigated by optical microscopy (OM), electron backscattering diffraction (EBSD), and transmission electron microscopy (TEM). The results show that with increasing the austenitizing temperature, the prior austenite grain size and block size increased, while the lath width decreased. Further, the yield strength and tensile strength increased due to the enhancement of the grain boundary strengthening. The fitting results reveal that only the relationship between lath width and strength followed the Hall–Petch formula of. Hence, we propose that lath width acts as the effective grain size (EGS) of strength in MCLA steel. In addition, the carbon content had a significant effect on the EGS of martensitic strength. In steels with lower carbon content, block size acted as the EGS, while, in steels with higher carbon content, the EGS changed to lath width. The effect of the Cottrell atmosphere around boundaries may be responsible for this change.

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“…Molybdenum had retarded carbon diffusion towards the austenite grain boundaries [7]. Investigation of Mo and B added steel with advanced techniques like atomic probe field ion microscope (AP-FIM) by researchers revealed the fine dispersive Ti-Mo carbonitrides (Ti,Mo)(C,N) and Mo-C clusters in asrolled steels [9].…”

Section: J Min Metall Sect B-metall 54 (3) B (2018) 339 -347mentioning

confidence: 99%

Effect of molybdenum addition on hardenability of chromium-boron steels used for press hardening applications

Deepa¹,

Sahoo²,

Dhua³

2018

J min metall B Metall

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Two laboratory heats of low-Carbon low-alloy steels, one with boron and chromium additions and other with boron, chromium and molybdenum additions were made and cast into pencil ingots. These ingots were hot-rolled to 2 mm sheets suitable for press hardening application in an experimental rolling mill. A detailed study was made on the effect of various alloying elements on the microstructure and mechanical properties of these steels. A significantly higher hardness (~496 VHN), yield strength (~1137 MPa) and ultimate tensile strength (~1673 MPa) with comparable elongation (~6%) could be achieved in the as rolled and water-quenched Mo-Cr-B steel in comparison to Cr-B steel under similar processing condition. Moreover, a reduction of critical cooling rate by10 o C/s was observed in this steel to obtain fully martensitic structure. The combined addition of boron, chromium and molybdenum was found to be more effective than that of boron and chromium in enhancing the microstructure and mechanical properties of boron-added steels. Additionally, a few hot compression tests were carried out to simulate the press hardening process of these experimental steels. It was found that one of the press hardening process parameters, viz., prior strain had a greater impact on the transformation behaviour of Cr-B and Mo-Cr-B steels during cooling.

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Atomic-scale study on segregation behavior at austenite grain boundaries in boron- and molybdenum-added steels

Cited by 92 publications

References 37 publications

Effect of Molybdenum Content on the Combined Effect of Boron and Molybdenum on Hardenability of Low-Carbon Boron-Added Steels

Effect of Molybdenum Content on the Combined Effect of Boron and Molybdenum on Hardenability of Low-Carbon Boron-Added Steels

The Effect of Lath Martensite Microstructures on the Strength of Medium-Carbon Low-Alloy Steel

Effect of molybdenum addition on hardenability of chromium-boron steels used for press hardening applications

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