Revisit Deformation Behavior of Lath Martensite

Harjo, Stefanus; Gong, Wu; Kawasaki, Takuro; Morooka, Shigenori; Yamashita, Takayuki

doi:10.2355/isijinternational.isijint-2022-207

Cited by 3 publications

(3 citation statements)

References 51 publications

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“…On the contrary, martensitic transformation in steels introduces high-density dislocations of 10 15 − 10 16 m − 2 , and some of their short-range motion as mobile dislocations can generate sufficient plastic strain. 1,[5][6][7][8] Therefore, in martensitic steels, the effect of newly-formed dislocations is small, and the onset of plastic deformation will be controlled by the average dislocation velocity of mobile dislocations dx/dt, as indicated by Eq. (6b).…”

Section: Resultsmentioning

confidence: 99%

“…A macroscopic mechanical test using a uniaxial tensile test is commonly used to evaluate the mechanical properties of martensitic steels. Especially, stress relaxation test, 1,[5][6][7][8] in which the crosshead is stopped at stress near the elastic limit, and the decrease in load caused by plastic strain is measured, is also used to evaluate the elastic limit. However, this method is not always easy, because it is sometimes difficult to prepare a specimen of sufficient dimensions from a fully quenched material.…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of Elastic-Plastic Deformation Behavior of Lath Martensite by Nanoindentation Technique

Shiki,

Nagashima,

Nakada

2024

ISIJ Int.

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It is well known that ferritic steels yield discontinuously with a clear yield point, while martensitic steels yield continuously with a low elastic limit followed by significantly large strain hardening.To evaluate the unique elastic-plastic deformation behavior of martensitic steels easily and accurately, nanoindentation tests were conducted using martensitic steels with lath martensitic structure, and the obtained results were then compared with that of ferritic steel while taking into account the pop-in phenomenon. In the normal load-displacement curves, ferritic steel had pop-in clearly, but no pop-in was observed for martensitic steels, regardless of carbon content. However, the analysis based on Hertz's contact theory made it possible to quantitatively evaluate the elastic limit of martensitic steel as well as ferritic steel. As a result, it was found that the elastic limit of martensitic steel is much lower than that of ferritic steel, and the plastic strain at yielding is also quite small. The plastic deformation behavior based on dislocation theory suggests that the yielding of ferritic steels is governed by dislocation nucleation and subsequent dislocation avalanche. In contrast, the yielding phenomenon of martensitic steels might be greatly influenced by the motion of pre-existing mobile dislocations introduced through martensitic transformation.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Evaluation of Elastic-Plastic Deformation Behavior of Lath Martensite by Nanoindentation Technique

Shiki,

Nagashima,

Nakada

2024

ISIJ Int.

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“…to re-evaluate the changes in the lattice constant of austenite during martensitic transformation 8,17,18) , tetragonality 19) , and the transformation and deformation behavior of martensite 20) . There are several reports on martensitic transformation behavior during quenching from high temperatures 8,17,18) .…”

Section: Introductionmentioning

confidence: 99%

Martensitic Transformation Behavior of Fe–Ni–C Alloys Monitored by <i>In-situ</i> Neutron Diffraction during Cryogenic Cooling

et al. 2024

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In-situ neutron diffraction measurements were performed on Fe-33Ni-0.004C alloy (33Ni alloy) and Fe-27Ni-0.5C alloy (27Ni-0.5C alloy) during cooling from room temperature to the cryogenic temperature (4 K) to evaluate changes in the lattice constants of austenite and martensite, and changes in the tetragonality of martensite due to thermally induced martensitic transformation.As the martensitic transformation progressed, the lattice constants of austenite in both alloys deviated to smaller values than those predicted considering the thermal shrinkage, accompanied by an increase in the full width at half maximum of austenite. The fresh martensite formed in both alloys had a body-centered tetragonal (BCT) structure, regardless of the carbon content. The tetragonality of martensite decreased with progressive martensitic transformation during cooling in the 33Ni alloy, but was almost constant in the 27Ni-0.5C alloy. This suggests that carbon is necessary to maintain the tetragonality of martensite during cooling. The tetragonality of martensite in the 27Ni-0.5C alloy decreased during room temperature aging because of carbon mobility.

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Effects of Manganese on Microstructure and Work-hardening Behavior of Low-carbon Lath Martensitic Steel

Ueno,

Fujimura,

Mitsuhara

et al. 2024

Tetsu-to-Hagane

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Microstructures of lath martensite have been studied intensively to understand their effect on the mechanical properties of steels. It is, however, said that the relation between microstructural factors and mechanical properties has not been clarified yet. The plastic deformation behavior of fully lath martensitic steels has become important because they are applied to automobile body structures such as bumper reinforcement. It is, therefore, important to understand the microstructural factors that control the work-hardening behavior of fully martensitic steels. Although we could not clarify differences in microstructural factors when manganese (Mn) concentrations of steels are altered, the work-hardening of 8 mass%Mn martensitic steel is much higher than that of 5 mass%Mn martensitic steel. It was found using the digital image correlation (DIC) method, that the strain concentration due to the in-lath-plane slip deformation is more developed in 5 mass%Mn martensitic steel than 8 mass%Mn martensitic steel. Transmission electron microscope (TEM) observations revealed the existence of two types of fine twins inside laths. Long twins that are parallel to the longitude of the lath are observed both in 5 mass%Mn and 8 mass%Mn martensitic steels. Short twins that partially cross the laths, on the other hand, can only be found in 8 mass%Mn martensitic steel. Since twin boundaries are high angle boundaries, the short twins are supposed to prevent the development of in-lath-plane slip deformation. This seems to be the mechanism of higher work-hardening behavior observed in 8 mass%Mn martensitic steel.

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Revisit Deformation Behavior of Lath Martensite

Cited by 3 publications

References 51 publications

Evaluation of Elastic-Plastic Deformation Behavior of Lath Martensite by Nanoindentation Technique

Evaluation of Elastic-Plastic Deformation Behavior of Lath Martensite by Nanoindentation Technique

Martensitic Transformation Behavior of Fe–Ni–C Alloys Monitored by <i>In-situ</i> Neutron Diffraction during Cryogenic Cooling

Effects of Manganese on Microstructure and Work-hardening Behavior of Low-carbon Lath Martensitic Steel

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