Anomalous microsegregation in Al–Si foundry alloys

Pedersen, L.; Arnberg, L.

doi:10.1016/s0921-5093(97)00490-5

Cited by 15 publications

(13 citation statements)

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“…Dons et al [62] showed that the anomalous segregation profile for Si was caused by diffusion of Si from the α-Al matrix to Si particles in s segregation profiles for Si were confirmed by solidification rates for all three alloys, see Figure hown The presented Cu concentrations in the centre of the dendrite arms show some variations and values of 1.2 wt% [63] and 0.6 wt% [64] are reported for an Al-7Si-3.5Cu alloy. The consistency in reported data is better for Mg [61,65] and is in line with data from the present investigation. Possible reasons for deviations in the reported results in the literature are differences in measurement method used, EDS or WDS, and the difficulty of finding a dendrite that is cut through its centre.…”

Section: Segregation Profiles Of Alloying Elementssupporting

confidence: 92%

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The heat treatment of Al–Si–Cu–Mg casting alloys

Sjölander

Seifeddine

2010

Journal of Materials Processing Technology

460

223

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Environmental savings can be made by increasing the use of aluminium alloys in the automotive industry as the vehicles can be made lighter. Increasing the knowledge about the heat treatment process is one task in the direction towards this goal. The aim of this work is to investigate and model the heat treatment process for Al-Si casting alloys. Three alloys containing Mg and/or Cu were cast using the gradient solidification technique to achieve three different coarsenesses of the microstructure and a low amount of defects.Solution treatment was studied by measuring the concentration of Mg, Cu and Si in the α-Al matrix using wavelength dispersive spectroscopy (WDS) after various times at a solution treatment temperature. A diffusion based model was developed which estimates the time needed to obtain a high and homogenous concentration of alloying elements for different alloys, temperatures and coarsenesses of the microstructure. It was shown that the yield strength after artificial ageing is weakly dependent on the coarseness of the microstructure when the solution treatment time is adjusted to achieve complete dissolution and homogenisation.The shape and position of ageing curves (yield strength versus ageing time) was investigated empirically in this work and by studying the literature in order to differentiate the mechanisms involved. A diffusion based model for prediction of the yield strength after different ageing times was developed for Al-Si-Mg alloys. The model was validated using data available in the literature. For Al-Si-Cu-Mg alloys further studies regarding the mechanisms involved need to be performed.Changes in the microstructure during a heat treatment process influence the plastic deformation behaviour. The Hollomon equation describes the plastic deformation of alloys containing shearable precipitates well, while the Ludwigson equation is needed when a supersaturated solid solution is present. When non-coherent precipitates are present, none of the equations describe the plastic deformation well. The evolution of the storage rate and recovery rate of dislocations was studied and coupled to the evolution of the microstructure using the Kocks-Mecking strain hardening theory.

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Section: Segregation Profiles Of Alloying Elementssupporting

confidence: 92%

“…The concentration profiles for Si for differe solidification rates have been studied by Pedersen et al [61]. gation profiles of Si, Mg and Cu in the α-nt segregation profile was observed, with higher Si concentration in the centre of the dendrite arm compared to the edges, for alloys solidified slowly.…”

Section: Segregation Profiles Of Alloying Elementsmentioning

confidence: 95%

The heat treatment of Al–Si–Cu–Mg casting alloys

Sjölander

Seifeddine

2010

Journal of Materials Processing Technology

460

223

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“…Higher levels of Si are observed at the edge of the dendrite compared to the centre for the samples with lower SDAS, which are also generally having higher overall Si concentrations compared to the two coarser microstructures. The result is in SDAS ~ 10 µm SDAS ~ 25 µm SDAS ~ 50 µm agreement with Pedersen et al [12] and Hons et al [13] and lately confirmed by hardness measurement confirmed by Seifeddine et al [14]. For the slowly solidified materials, Si could be diffused from the α-Al matrix to Si particles in the eutectic after solidification.…”

Section: Microstructure Characterizationsupporting

confidence: 79%

On the Role of Copper and Cooling Rates on the Microstructure, Defect Formations and Mechanical Properties of Al-Si-Mg Alloys

Seifeddine¹,

Sjölander²,

Bogdanoff³

2013

MSA

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This paper aims to assess the role of Cu on Al-Si-Mg alloys, in a range of 0 -5 wt%, qualitatively on microstructure, defect formation, in terms of porosity, and strength in the as-cast conditions. The ternary system of Al-Si-Mg, using the A356 alloy as a base material, were cast using the gradient solidification technique; applying three different solidification rates to produce directional solidified samples with a variety of microstructure coarsenesses. Microstructural observations reveal that as the Cu levels in the alloys are increased, the amounts of intermetallic compounds as well as the Cu concentration in the α-Al matrix are increased. Furthermore, the level of porosity is unaffected and the tensile strength is improved at the expense of ductility.

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“…The PFZ around the eutectic particles was attributed to the loss of Si by diffusion to the eutectic particles. In another study, Pedersen and Arnberg [13] investigated the microsegregation of Si within Al dendrites by microprobe analysis and found that peak concentration was in the midpoint of the dendrites. These results were later verified by simulations of Dons et al, [14] who concluded Fig.…”

Section: B Quench Precipitatesmentioning

confidence: 99%

Quench Sensitivity of an Al-7 Pct Si-0.6 Pct Mg Alloy: Characterization and Modeling

Tiryakioğlu

Shuey

2007

Metall Mater Trans B

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The quench sensitivity of a cast Al-7 wt pct Si-0.6 wt pct Mg alloy was characterized by tensile tests and scanning electron microscopy. Specimens were cooled from the solution treatment temperature following 58 different cooling paths including interrupted and delayed quenches. Analysis of the microstructure showed that quench precipitates were Mg 2 Si (b), which nucleated heterogeneously on Si eutectic particles as well as in the aluminum matrix, presumably on dislocations. The quench sensitivity of the alloy's yield strength was modeled by multiple Ccurves, using an improved methodology for quench factor analysis. The three C-curves used in the model represented loss of solute by (1) diffusion of Si to eutectic particles, (2) precipitation of b on Si eutectic particles, and (3) precipitation of b in the matrix. The model yielded a R 2 of 0.994 and a root-mean-square error (RMSE) of 7.4 MPa. The model and the implications of the results are discussed in the article.

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Anomalous microsegregation in Al–Si foundry alloys

Cited by 15 publications

References 1 publication

The heat treatment of Al–Si–Cu–Mg casting alloys

The heat treatment of Al–Si–Cu–Mg casting alloys

On the Role of Copper and Cooling Rates on the Microstructure, Defect Formations and Mechanical Properties of Al-Si-Mg Alloys

Quench Sensitivity of an Al-7 Pct Si-0.6 Pct Mg Alloy: Characterization and Modeling

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