Anisotropic distribution of the micro residual stresses in lath martensite revealed by FIB ring-core milling technique

Archie, Fady Mamdouh Fawzy; Mughal, Muhammad Zeeshan; Sebastiani, Marco; Bemporad, Edoardo; Zaefferer, Stefan

doi:10.1016/j.actamat.2018.03.030

Cited by 48 publications

(15 citation statements)

References 37 publications

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“…They are hydrostatic and lead to a shift of the diffraction peaks of the phases.Internal stress heterogeneities in the martensitic microstructure have been fewly addressed in literature. Thus, on one hand, Archie et al[39] and Fukui et al[40] recently reported an anisotropic strain distribution by SEM-FIB based ring-core method at the scale of the martensite variants, while Nakada et al have reported an anisotropic distribution of the micro residual strains in the austenite[36]. It is possible to assume that the effect of the internal stresses on the FWHM might become more important with the progress of the transformation as the size effect is more important.In our case, the experimental method used is not able to deconvolute internal stress heterogeneities from the dislocation density contribution within the phases.…”

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confidence: 99%

Dislocation densities in a low-carbon steel during martensite transformation determined by in situ high energy X-Ray diffraction

Macchi

Gaudez

Géandier

et al. 2021

Materials Science and Engineering: A

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The evolution of the dislocation densities in martensite and in austenite during the quench of a low-carbon (0.215 wt.% C) steel is investigated in situ by the mean of a High Energy X-Ray Diffraction experiment on a synchrotron beamline. The line configuration offers an excellent time resolution well adapted to the studied martensitic transformation kinetics. The mean density of dislocations in martensite increases as the transformation proceeds confirming that dislocations are not homogeneously distributed between the laths in agreement with some recent post-mortem observations. The resulting spatial distribution of dislocations and the associated strain-hardening support the views assuming that lath martensite is a heterogeneous microstructure and behaves as a "multiphase" aggregate. In austenite, the increase in dislocation densities is even more significant meaning that austenite in martensite is also a hard phase, contradicting some recent theories attributing to films of retained austenite a major role in the plasticity of martensite.

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confidence: 99%

Dislocation densities in a low-carbon steel during martensite transformation determined by in situ high energy X-Ray diffraction

Macchi

Gaudez

Géandier

et al. 2021

Materials Science and Engineering: A

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“…Both samples reached a milling depth of ~3 μm (30% of the ring diameter). It is reported from previous literature that a milling depth ≥20% of the ring diameter should sufficiently relax the pillar to provide reliable results [36,37]. The FIB-DIC results for both samples are displayed in Fig.…”

Section: Residual Stress Relaxationmentioning

confidence: 85%

Reducing hot tearing by grain boundary segregation engineering in additive manufacturing: example of an AlxCoCrFeNi high-entropy alloy

et al. 2021

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One major hindrance that alloy design for additive manufacturing (AM) faces nowadays is hot tearing. Contrary to the previous works which either try to reduce solidification range or introduce grain refinement, the current work presents a new approach of employing segregation engineering to alter the residual stress states at the interdendritic and grain boundary regions and consequently prevent hot tearing. Here, in situ Al alloying is introduced into an existing hot-cracking susceptible highentropy alloy CoCrFeNi. It is found that within a certain range of compositions, such as Al0.5CoCrFeNi, the hot crack density was drastically decreased. During the solidification of this specific alloy composition, Al is firstly ejected from the primary dendritic face-centred cubic (FCC) phase and segregates into the interdendritic regions. Spinodal decomposition then occurs in these Al-enriched regions to form the ordered B2 NiAl and disordered body-centred cubic (BCC) Cr phases. Due to the higher molar volume and lower homologous temperatures of these B2/BCC phases, the inherent residual strain is accommodated and transformed from a maximum 0.006 tensile strain in CoCrFeNi to a compressive strain of ~0.001 in Al0.5CoCrFeNi. It is believed that this grain boundary segregation engineering method could provide a new pathway to systematically counteract the hot tearing problem in additive manufacturing of metals and alloys, using available thermodynamic and kinetic database information.

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“…Recently, Archie et al (2018) experimentally determined considerable residual stresses in a lath martensite microstructure by using a micro ring-core milling technique. It could be shown that anisotropically distributed residual micro-stresses correlate with the morphology and lath crystallography.…”

Section: Discussionmentioning

confidence: 99%

Parameterization of a Non-local Crystal Plasticity Model for Tempered Lath Martensite Using Nanoindentation and Inverse Method

2019

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Anisotropic distribution of the micro residual stresses in lath martensite revealed by FIB ring-core milling technique

Cited by 48 publications

References 37 publications

Dislocation densities in a low-carbon steel during martensite transformation determined by in situ high energy X-Ray diffraction

Dislocation densities in a low-carbon steel during martensite transformation determined by in situ high energy X-Ray diffraction

Reducing hot tearing by grain boundary segregation engineering in additive manufacturing: example of an AlxCoCrFeNi high-entropy alloy

Parameterization of a Non-local Crystal Plasticity Model for Tempered Lath Martensite Using Nanoindentation and Inverse Method

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