Elastic Strain Measurement of Miniature Tensile Specimens

Akbary, Farideh Hajy; Santofimia, M.J.; Sietsma, Jilt

doi:10.1007/s11340-013-9785-7

Cited by 27 publications

(12 citation statements)

References 11 publications

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“…Partial martensite transformation was found to accelerate the subsequent bainite transformation, because the dislocations introduced by martensite transformation are profoundly contributing to the bainite acceleration phenomenon caused by the pre‐existing martensite . Moreover, bainite transformation during I&Q&P heat treatment is a very complex process, because it can be affected by carbon partitioning and precipitation of carbides upon different quenching and partitioning temperatures, and conversely bainite transformation has an effect on the stability of retained austenite …”

Section: Introductioncontrasting

confidence: 61%

“…The bainite transformation during partitioning has been demonstrated in many studies . Furthermore, the reaction is unavoidable, especially in low carbon and low alloy steels . The supersaturated first martensite may have an effect on the bainite transformation.…”

Section: Introductionmentioning

confidence: 99%

“…[28,[31][32][33] Furthermore, the reaction is unavoidable, especially in low carbon and low alloy steels. [34] The supersaturated first martensite may have an effect on the bainite transformation. Partial martensite transformation was found to accelerate the subsequent bainite transformation, because the dislocations introduced by martensite transformation are profoundly contributing to the bainite acceleration phenomenon caused by the pre-existing martensite.…”

Section: Introductionmentioning

confidence: 99%

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Modeling of Bainite Transformation During Partitioning Process and Atomic‐Scale Characterization of Bainite

Song

Lü

et al. 2018

steel research int.

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This paper presents a detailed investigation of the interaction between bainite transformation and carbon partitioning during isothermal holding of intercritical heating, quenching, and partitioning (I&Q&P) steel. The kinetics of isothermal bainite transformation is modeled based on the assumption of displacive mechanism. A systematic analysis of the autocatalytic parameters extracted from the fitting curves reveals that autocatalysis plays only a minor role in bainite transformation due to quite small size of parent austenite grains transforming into bainite, independent from each other. Atom probe tomography (APT) is used to investigate the localized composition changes at the interface between bainitic ferrite and retained austenite. The results indicate that carbon enrichment of austenite occurs and Mn atoms segregate at phase grain boundary. Furthermore, in terms of the thermodynamic analysis, bainitic ferrite forms under diffusionless growth followed by tempering, and in present work, the growth of bainitic ferrite can be divided into two parts: bainite transformation quickly (BTQ) and bainite transformation slowly (BTS).

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Section: Introductioncontrasting

confidence: 61%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Modeling of Bainite Transformation During Partitioning Process and Atomic‐Scale Characterization of Bainite

Song

Lü

et al. 2018

steel research int.

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“…Microtensile tests were performed using a Deben Microtest 5000N Tensile Stage. Elongation of the miniature specimens was determined by subtracting the machine compliance from the total crosshead displacement, on the basis of the approach that was given in [34]. This step is taken due to the fact that the machine compliance is recorded along with the specimen elongation as the crosshead displacement [34].…”

Section: Microtensile Testmentioning

confidence: 99%

An improved X-ray diffraction analysis method to characterize dislocation density in lath martensitic structures

HajyAkbary

Sietsma

Böttger

et al. 2015

Materials Science and Engineering: A

262

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“…A method to estimate strain from the crosshead displacement has been investigated by Akbary et al [25] using mathematical models to correct for the (elastic) deformations of the shoulder areas and of the machine itself. In parallel, strain was optically measured.…”

Section: Digital Image Correlationmentioning

confidence: 99%

Characterisation of weld heterogeneity through hardness mapping and miniature tensile testing

Bally

Waele

Verleysen

et al. 2015

SCAD

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Abstract:Welding is a widely adopted industrial process used for joining components. A fusion weld has a highly heterogeneous microstructure and characterisation of strength heterogeneity is difficult because of the potentially large variations over a limited distance. Hardness mapping and miniature tensile tests are two distinct approaches to this problem. This paper reports on the possibilities and limitations of both techniques. Hardness mapping is a well-documented procedure as opposed to miniature tensile testing, where the dimensions of the dogbone shaped specimens are smaller than what standards prescribe. A particular challenge is the measurement of strains in such small specimens. The authors have achieved this measurement by means of Digital Image Correlation (DIC). To that end, a sufficiently fine speckling method has been developed.Keywords: heterogeneity; hardness mapping; miniature tensile testing; DIC INTRODUCTIONWelding is one of the most common joining methods due to its generally high production speed and low associated costs. It is often associated with flexibility, integrity and reliability [1]. An example application showing the economic importance of welding is pipeline installation. Costs associated to fusion welding are estimated to make up 20% of the total cost of pipe laying. These include aligning the pipe sections, cleaning and grinding, welding, checking the weld for flaws and coating the weld [2].Notwithstanding the economical appeal of welding, the localized application of heat and melting results in a high susceptibility to material discontinuities, flaws and residual stresses, whose presence may lead to structural failure and lifetime reduction. The prediction of weld flaw acceptability ('structural integrity') is hampered by the potential presence of strongly heterogeneous microstructures. Modern day weld flaw assessment ignores this heterogeneity by assuming a homogeneous weld. As such, a generally accepted method to characterise weld heterogeneity does not yet exist. STATE OF THE ARTHeterogeneity is inherent to fusion welds, because in order to melt the weld metal and fuse it with the base metal, heat has to be locally applied. For thicker sections, weldments are created in several passes (deposition of multiple layers), resulting in a variety of zones undergoing a succession of particular heat cycles. The heat cycle determines what the microstructure transforms into, each structure having a different stress-strain response. Not only the weld metal is heterogeneous due to this, but the heat affected zone (HAZ) of the base metal (heated but non-melted metal in close vicinity of the weld) also transforms.Many conventional steel welds show a hardened HAZ due to the occurrence of stronger microstructures. In contrast, a broad range of high strength low alloy steels obtain their properties from a fine grain size, resulting from a specific heat treatment, often combined with mechanical deformation. These steels may show a softened HAZ due to grain coarsening. To quantify variations ...

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Elastic Strain Measurement of Miniature Tensile Specimens

Cited by 27 publications

References 11 publications

Modeling of Bainite Transformation During Partitioning Process and Atomic‐Scale Characterization of Bainite

Modeling of Bainite Transformation During Partitioning Process and Atomic‐Scale Characterization of Bainite

An improved X-ray diffraction analysis method to characterize dislocation density in lath martensitic structures

Characterisation of weld heterogeneity through hardness mapping and miniature tensile testing

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