Monitoring of Bainite Transformation Using in Situ Neutron Scattering

Nishijima, Hikari; Tomota, Yō; Su, Yuhua; Gong, Wu; Suzuki, Jun–ichi

doi:10.3390/met6010016

Cited by 10 publications

(4 citation statements)

References 32 publications

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“…Thus, finally the microstructure will consist of partially carbon-supersaturated plates of bainitic ferrite, α b , and C enriched austenite (γ + ), the latter as thin films between ferrite plates and submicron blocks between sheaves of bainite [5,6]. This microstructure has a high hardness and strength, owing to the combined influence of several types of obstacles to dislocation motion, such as interfaces and dislocations, and also to solid solution strengthening and to the interaction between carbon and defects [3,[7][8][9][10][11][12][13][14][15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Quantitative Assessment of the Time to End Bainitic Transformation

Santajuana

Eres-Castellanos

Ruiz-Jimenez

et al. 2019

Metals

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Low temperature bainite consists of an intimate mixture of bainitic ferrite and retained austenite, usually obtained by isothermal treatments at temperatures close to the martensite start temperature and below the bainite start temperature. There is widespread belief regarding the extremely long heat treatments necessary to achieve such a microstructure, but still there are no unified and objective criteria to determine the end of the bainitic transformation that allow for meaningful results and its comparison. A very common way to track such a transformation is by means of a high-resolution dilatometer. The relative change in length associated with the bainitic transformation has a very characteristic sigmoidal shape, with low transformation rates at the beginning and at end of the transformation but rapid in between. The determination of the end of transformation is normally subjected to the ability and experience of the “operator” and is therefore subjective. What is more, in the case of very long heat treatments, like those needed for low temperature bainite (from hours to days), differences in the criteria used to determine the end of transformation might lead to differences that might not be assumable from an industrial point of view. This work reviews some of the most common procedures and attempts to establish a general criterion to determine the end of bainitic transformation, based on the differential change in length (transformation rate) derived from a single experiment. The proposed method has been validated by means of the complementary use of hardness measurements, X-ray diffraction and in situ high energy X-ray diffraction.

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Section: Introductionmentioning

confidence: 99%

Quantitative Assessment of the Time to End Bainitic Transformation

Santajuana

Eres-Castellanos

Ruiz-Jimenez

et al. 2019

Metals

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“…In situ investigations on microstructure and phase evaluations from the bulk of material are most important to develop modern high-strength, transformation-induced plasticity steels. Here, Nishijima et al [7] present small-angle neutron scattering simultaneously taken with dilatometry in order to determine the precipitation and evolution of ferrite in austenite, after quenching from 1173 K to 573 K and subsequent holding. Furthermore, the quantitative phase evolution is monitored in wide-momentum-transfer neutron diffraction, revealing not only phase fractions but also strain in the lattice parameters.…”

Section: Sintering Techniques and Microstructure Evolutionmentioning

confidence: 99%

Metals Challenged by Neutron and Synchrotron Radiation

2018

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In the past one and a half decades, neutron and synchrotron radiation techniques have come to the forefront as an excellent set of tools for the wider investigation of material structures and properties, becoming available to a large user community. This holds especially true for metals, which are a fascinating class of materials with both structural and functional applications. With respect to these application classes, metals are used to engineer bridges and automotive engines as well as to exploit magnetic and electric properties in computer storage, optics, and electronics. Both neutron sources and synchrotrons are large user facilities of quantum-beam installations [3] with the implementation of a common accelerator or nuclear reactor-based source, often serving over 50 beamlines simultaneously and even more end stations. Up to a few thousand experiments are undertaken yearly, utilizing specialized beam conditions, sample environments, and detection systems. Their variations range across spectroscopy, diffraction, small-angle scattering, and inelastic scattering for sample sizes ranging from nanometers to meters. Examples of such installations can be found in the Topical Collection Facilities of Metals' sister journal Quantum Beam Science. The scope of the present Special Issue in Metals comprises articles on research case studies on individually selected systems. Fields of interest range from engineering, through materials design, to fundamental materials science, including non-exclusively, strain scanning, texture analysis, phase transformation, precipitation, microstructure reconstruction, crystal defects, atomic structures (both crystalline and amorphous), order and disorder, kinetics, timeresolved microstructure evolution, local structure correlations, phonons, deformation and transformation mechanisms, response to extreme conditions, local and integrated studies, both within the bulk and at interfaces. Regarding the breadth of the discipline, this contribution is not exhaustive by far, but stimulates important and evolving studies throughout the metals community.

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“…Here, Nishijima et al [7] present small-angle neutron scattering simultaneously taken with dilatometry in order to determine the precipitation and evolution of ferrite in austenite, after quenching from 1173 K to 573 K and subsequent holding. Furthermore, the quantitative phase evolution is monitored in wide-momentum-transfer neutron diffraction, revealing not only phase fractions but also strain in the lattice parameters.…”

Section: Sintering Techniques and Microstructure Evolutionmentioning

confidence: 99%