An integrated model for the post-solidification shape and grain morphology of fusion welds

Kidess, A.; Tong, Min; Duggan, Gregory; Browne, David J.; Kenjereš, Saša; Richardson, I.M.; Kleijn, Chris R.

doi:10.1016/j.ijheatmasstransfer.2015.01.144

Cited by 17 publications

(13 citation statements)

References 41 publications

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“…The competitive growth of grains, influenced by the transient thermal conditions and solidification characteristics of the weld metal, determines the morphology of the grain structure [52,53]. In fusion welding axial, columnar and equiaxed grain morphologies can be observed depending on the thermal gradient, cooling rate and use of grain refining particles [52,54,55]. Therefore, the appearance of the grains on one cross section may not be representative of the grain morphology [56], causing bias for the assumed relationship between surface area and volume (Eq.…”

Section: Discussionmentioning

confidence: 99%

Characterisation of local grain size variation of welded structural steel

et al. 2016

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Previously, it has been shown that the grain size distribution plays an important role in the mechanical properties of welded steel. In the previous investigation, the volume-weighted average grain size has been shown to capture the influence of grain size distribution, resulting in a better fitting Hall-Petch relationship between grain size and hardness. However, the previous studies exclude the effects arising from local variation in grain size. In this paper, the grain size measurement methods are extended for the characterisation of the local grain size variation, which is significant for welded joints and can have an adverse effect on mechanical properties. The local gradient of grain size variation and its dependency on measurement direction are considered. In addition, examples of grain size and hardness variation are shown for S355 base metal and two weld metals, and characteristic differences are highlighted and discussed. The coarse-grained areas of a heterogeneous microstructure are found to have lower hardness than fine-grained areas. However, the surrounding microstructure, i.e. local grain size gradient, has an influence on the measured hardness values.

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Section: Discussionmentioning

confidence: 99%

Characterisation of local grain size variation of welded structural steel

et al. 2016

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“…Using computational fluid dynamics (CFD), computer simulation has been extensively employed in the prediction of flow features of metal processing, including such as casting [13] and welding [14,15]. In comparison, CFD modelling of melt conditioning is relatively rare.…”

Section: Introductionmentioning

confidence: 99%

Identification of key liquid metal flow features in the physical conditioning of molten aluminium alloy with high shear processing

Tong

Patel

Stone

et al. 2017

Computational Materials Science

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Although treating molten alloy with high shear processing (HSP) can dramatically refine the microstructure of solidified aluminium alloys, it was also recently employed as part of an effective route to purification of contaminated aluminium alloy scrap. The key mechanisms of HSP include the dispersion of large aluminium oxide films and clusters into very fine oxide particles by the high shear rate, and the redistribution of bulk melt by the agitation. These fine oxides act as nucleation sites for iron-based intermetallic phases, the formation of which is a precursor to purification of the alloy. Macroscopic flow features of HSP, such as flow rate and shear rate, influence its performance significantly. Simulation based on Computational Fluid Dynamics was used to predict key features of fluid flow during HSP in a static direct chill (DC) caster. It was found that the distribution of shear rate and mass flow rate is highly nonuniform in the caster, and only in the close vicinity of the mixing head is there a relatively high level of shear rate and effective melt agitation. Therefore, effective dispersion of oxide films and clusters, and resulting significant nucleation of the intermetallics and/or primary aluminium phase, can only occur near the mixing head, and not throughout the whole crucible. Confidence in the model validity was built, by comparison with post-solidification microstructures in a previous experiment with similar process parameters and geometry.

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“…During the solidification of the molten pool, the ratio G/Rw along the trailing pool boundary has an important influence on the weld solidification structure morphologies [28][29][30][31]. With the decrease of the ratio G/Rw, the constitutional undercooling in front of the trailing pool boundary will increase, and the more equiaxed grains can form in the molten pool and compete with the epitaxial columnar grains [21].…”

Section: The Ca Model For Weld Solidification Structurementioning

confidence: 99%

Macro-micro modeling and simulation for the morphological evolution of the solidification structures in the entire weld

Han

2017

International Journal of Heat and Mass Transfer

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The heat and mass transfer and the morphological evolution of the various weld solidification structures for the entire weld were simulated by the macro-micro coupled model which combined the welding process and the solidification structures in the molten pool. The weld profile were calculated for different welding conditions, and the effects of the welding parameters on the solidification conditions were analyzed along the trailing pool boundary. The formation mechanism of the axial structure and the equiaxed grains in the weld were studied by the developed model. The results indicate that the temperature gradient G, solidification rate Rw, and the ratio G/Rw along the trailing pool boundary are related with the location in the weld and the welding parameters. When the weld solidification structure is only consisted with the epitaxial columnar grains from the fusion boundary, the axial structure forms in the central region of the weld at low welding speeds owing to the anisotropic kinetics of the columnar grains. When the heterogeneous nucleation occurs in the molten pool, the weld structure is directly determined by the competitive growth between the columnar and new nucleated grains. At low welding speeds, the preferential orientations of the survival grains get closer to the welding direction with the decrease of the distance to the weld center.

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An integrated model for the post-solidification shape and grain morphology of fusion welds

Cited by 17 publications

References 41 publications

Characterisation of local grain size variation of welded structural steel

Characterisation of local grain size variation of welded structural steel

Identification of key liquid metal flow features in the physical conditioning of molten aluminium alloy with high shear processing

Macro-micro modeling and simulation for the morphological evolution of the solidification structures in the entire weld

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