Effect of intensive melt shearing on the formation of Fe-containing intermetallics in LM24 Al-alloy

Ht, Li; Ji, Shouxun; Wang, Y; Xia, Mingxu; Fan, Z.

doi:10.1088/1757-899x/27/1/012075

Cited by 6 publications

(7 citation statements)

References 16 publications

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“…2e), reveal that the in-situ spinel particles with such size distributions as those formed using the high shear technology can refine coarse α-AlFeMnSi phases in LM24 alloys. This result is in strong agreement with our previous study of coarse α-AlFeMnSi in A380 alloy refined by intensive melt shearing [40], and with the experimental results of Cao and Campbell that the MgAl2O4 is the good nucleation substrate for α-Fe phase [16][17].…”

Section: Resultssupporting

confidence: 93%

Improve mechanical properties of high pressure die cast Al9Si3Cu alloy via dislocation enhanced precipitation

Zhang

Wang

Lordan

et al. 2019

Journal of Alloys and Compounds

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To improve the properties of high pressure die cast Al9Si3Cu alloy, melt treatment via high shear was employed to form fine in-situ MgAl2O4 particles which act as potential nuclei to refine α-Al grains whilst providing reinforcement to enhance the tensile strengths of the alloy. Experimental results showed that the naturally formed MgAl2O4 particles in the alloy melt were approximately 1 µm in diameter and are very limited in number as observed in the concentrated samples obtained via filtration. With the implementation of the high shear technology on the alloy melt, it is possible to synthesize a large number of fine MgAl2O4 particles which were approximately 80 nm to 300 nm in diameter. The yield strength of the alloy containing such in-situ sub-nano-sized particles was found to increase from 147 MPa to 169 MPa in the as-cast state. Following treatment with direct ageing at 155°C only, the yield strength of the alloy treated with high melt shear was found to increase by 128 MPa, ultimately achieving a yield strength and ultimate tensile strength of 297 MPa and 423 MPa respectively. The improvement of the mechanical properties of the alloy is attributed to the fine and uniform microstructure achieved by the enhanced heterogeneous nucleation of both α-Al grains and α-AlFeMnSi intermetallic compound via the in-situ MgAl2O4 particles, and also to the enhanced precipitation strengthening trigged by the increased dislocation density caused by the in-situ MgAl2O4 particles.

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Section: Resultssupporting

confidence: 93%

Improve mechanical properties of high pressure die cast Al9Si3Cu alloy via dislocation enhanced precipitation

Zhang

Wang

Lordan

et al. 2019

Journal of Alloys and Compounds

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“…1 wt% or higher), the ironbearing intermetallics normally precipitate before the appearance of -Al phase [6]. The lattice misfit between the aluminium oxide and iron bearing intermetallics was also found to be very low [7]. Therefore, the fine oxide particles act as potent nucleation sites for both the intermetallic and α-Al phases [8,9], during the solidification of aluminium alloys, and hence refine the microstructure of corresponding cast samples.…”

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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“…The implementation of the technology on large vessels requires an increase in the size of the unit and still further analysis, by computational fluid dynamic (CFD) modelling [51] and experimental validation [52], on the fluid flow and key features of the high shear processing. At this stage, the oxide agglomerates in the melt are finely dispersed because of the intensive melt shearing [35][36][37] and the composition and temperature are quickly homogenized by the strong macroscopic flow provided by the rotor-stator unit. dynamic (CFD) modelling [51] and experimental validation [52], on the fluid flow and key features of the high shear processing.…”

Section: The High Shear Melt Conditioning Technology Setup For De-iro...mentioning

confidence: 99%

“…dynamic (CFD) modelling [51] and experimental validation [52], on the fluid flow and key features of the high shear processing. At this stage, the oxide agglomerates in the melt are finely dispersed because of the intensive melt shearing [35][36][37] and the composition and temperature are quickly homogenized by the strong macroscopic flow provided by the rotor-stator unit.…”

Section: The High Shear Melt Conditioning Technology Setup For De-iro...mentioning

confidence: 99%

“…The use of high shear melt conditioning (HSMC) technology [32][33][34], developed within the Brunel Centre for Advanced Solidification Technology (BCAST) at Brunel University London, can overcome some of these problems. It can fragment and disperse the large oxide films and clusters into very fine and uniformly distributed individual particles [35,36], thereby enhancing the nucleation of intermetallic phases [37], and at the same time maximize the effect of the alloy chemistry so no additions in excess are required to enhance the formation of Fe-rich phases. In this paper, we present an overview of the progress made during the LiME Hub program to increase our understanding of the P-Fe-IMC precipitation-separation method and also to evaluate the effect of the developed HSMC technology to improve the efficiency of iron removal from aluminium melts, so the process becomes more practical and sustainable to be implemented in the recycling industry.…”

Section: Introductionmentioning

confidence: 99%

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De-Ironing of Aluminium Alloy Melts by High Shear Melt Conditioning Technology: An Overview

Lazaro-Nebreda

Patel

Al-Helal

et al. 2022

Metals

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The main problem of recycling aluminium scrap is the gradual accumulation of impurities, especially iron, which tend to form undesired intermetallic compounds that affect the integrity and the mechanical performance of the castings. In this paper, we aim to provide an overview on the topic of iron removal from aluminium melts through primary intermetallic precipitation and the progress made during the LiME Hub project to understand the process and to develop a more efficient procedure. We cover both thermodynamic analysis and experimental validation. We found that high shear melt conditioning technology enhances the typically slow nucleation and growth of the dense primary intermetallics, speeding up their sedimentation and allowing a faster removal of Fe from the melt by simple gravity sedimentation. It also promotes the formation of smaller and more compact Fe-rich intermetallics, allowing an increased volume fraction recovery and mitigating their effect of being present in the final castings. The technology is not limited to batch processing, with a 90% efficiency, but can also be applied to continuous melt treatment of aluminium scrap, with currently 60% efficiency, and could be combined with other solid–liquid separation techniques to increase the purification efficiency even more.

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Effect of intensive melt shearing on the formation of Fe-containing intermetallics in LM24 Al-alloy

Cited by 6 publications

References 16 publications

Improve mechanical properties of high pressure die cast Al9Si3Cu alloy via dislocation enhanced precipitation

Improve mechanical properties of high pressure die cast Al9Si3Cu alloy via dislocation enhanced precipitation

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

De-Ironing of Aluminium Alloy Melts by High Shear Melt Conditioning Technology: An Overview

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