Granular deformation mechanisms in semi-solid alloys

Gourlay, C.M.; Dahle, A. K.; Nagira, Tomoya; Nakatsuka, Noriaki; Nogita, Kazuhiro; Uesugi, Kentaro; Yasuda, Hideyuki

doi:10.1016/j.actamat.2011.04.038

Cited by 91 publications

(78 citation statements)

References 41 publications

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“…The synchrotron experimental procedure has been described in previous publications [8,14,16] and is schematized in Figure 1. It consisted of the specimen being held in a square, hollowed out, 200 µm thick Al2O3 mould sandwiched in between two 100 µm thick sapphire plates and held in between two boron nitride plates.…”

Section: Methodsmentioning

confidence: 99%

Dilatancy in semi-solid steels at high solid fraction

et al. 2017

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The study of mushy-zone deformation in steels is important for limiting defect formation in continuous casting. Here, we use in situ synchrotron radiography to quantify the shear deformation mechanisms of an equiaxed carbon steel at a solid fraction >0.9 and to understand how these mechanisms lead to casting defects. We show that the grain assembly undergoes shear-induced dilation (Reynolds' dilatancy) which opens liquid-filled fissures and cracks at high solid fraction. We further show a complex interaction between grain rearrangement, grain deformation and local coarsening, where rearrangement reduces the grain-grain contact area and coordination number which alters the stress network and also drives coarsening as grains move apart.

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Section: Methodsmentioning

confidence: 99%

Dilatancy in semi-solid steels at high solid fraction

et al. 2017

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“…7 Moreover, the exact mechanical loading within the material is not known as the deformation, localized in the hottest part of the specimen, is not measured. These tests are currently limited to Al-Cu alloys 8 to get a good contrast between the liquid and solid phases, and the alloy is tested after heating to the correct temperature within the solidification interval and not during solidification from the fully liquid state. The last point is particularly detrimental as solidifying microstructures are different from those obtained after heating owing to dendrite coarsening and redistribution of solute elements.…”

Section: Introductionmentioning

confidence: 99%

Determination of Coherency and Rigidity Temperatures in Al-Cu Alloys Using In Situ Neutron Diffraction During Casting

Drezet

Mireux

Száraz

et al. 2014

JOM

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The rigidity temperature of a solidifying alloy is the temperature at which the solid phase is sufficiently coalesced to transmit tensile stress. It is a major input parameter in numerical modeling of solidification processes as it defines the point at which thermally induced deformations start to generate internal stresses in a casting. This temperature has been determined for an Al-13 wt.% Cu alloy using in situ neutron diffraction during casting in a dog-bone-shaped mold. This setup allows the sample to build up internal stress naturally as its contraction is not possible. The cooling on both sides of the mold induces a hot spot at the middle of the sample that is irradiated by neutrons. Diffraction patterns are recorded every 11 s using a large detector, and the very first change of diffraction angles allows for the determination of the rigidity temperature. We measured rigidity temperatures equal to 557°C and 548°C depending on the cooling rate for grain refined Al-13 wt.% Cu alloys. At a high cooling rate, rigidity is reached during the formation of the eutectic phase. In this case, the solid phase is not sufficiently coalesced to sustain tensile load and thus cannot avoid hot tear formation.

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“…Particular research highlights have been the study of the role of solute build-up on remelting-driven fragmentation [12], the observa-tion of misorientations emerging during solidification [13,14], imaging eutectic solidification [15,16] and identifying the importance of granular behaviour in semi-solid alloys [17].…”

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Dendrite Bending during Directional Solidification

Aveson¹,

Reinhart²,

Nguyen-Thi³

et al. 2012

Superalloys 2012 (Twelfth International Symposium)

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In order to ascertain the origin of deformation and sub-grains in single crystal castings, an in situ, time-resolved X-ray radiographic imaging experiment was performed at the BM05 beam line of the European Synchrotron Radiation Facility (ESRF). This provided direct experimental evidence of the origin of crystallographic misorientation during the directional solidification of the nickel-based superalloy CMSX4. Solidification monitoring revealed that dendrites deform by bending and possibly torsion, and with deformation occurring early during dendrite growth, influencing the establishment of the dendritic array. These observations were related with electron backscattered diffraction data from ex situ samples. The bending and torsion contributions to deformation were extracted from the electron backscattered diffraction data using a data analysis scheme capable of isolating the deformation modes. In the component tested, bending was identified as the predominant deformation mode in sub-grain formation, but torsion effects were also seen to be significant.

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Granular deformation mechanisms in semi-solid alloys

Cited by 91 publications

References 41 publications

Dilatancy in semi-solid steels at high solid fraction

Dilatancy in semi-solid steels at high solid fraction

Determination of Coherency and Rigidity Temperatures in Al-Cu Alloys Using In Situ Neutron Diffraction During Casting

Dendrite Bending during Directional Solidification

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