Rare earth concentration in the primary Si crystal in rare earth added Al-21wt.%Si alloy

Chang, Joonyeon; Kim, G.H.; Moon, In-Ge; Choi, Chong-Sool

doi:10.1016/s1359-6462(98)00168-7

Cited by 90 publications

(43 citation statements)

References 8 publications

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“…It was found that adding modifier is the most popular and effective method to refine the primary silicon [3][4][5] . The effective refinement of primary Si can be obtained through the addition of some modifiers, such as P [4][5][6] , rare earth (RE) [7,8] , etc. However, the use of P can result in serious air pollution, and the costly RE used to refine primary Si is poor effective.…”

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confidence: 99%

Effects of ZnS modification on primary Si in hypereutectic Al-Si alloy

Sun

Si³

et al. 2017

China Foundry

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A s an important cast alloy, hypereutectic Al-Si alloy has a low expansion coefficient and density, good cast performance and high wear resistance. However, with the increasing of silicon content, a large number of coarse and irregular lumps of primary silicon and needle-like eutectic silicon can be observed, which seriously decreases the comprehensive performance of the alloy. Therefore, primary silicon must be refined to achieve the fine dispersive Si phase with desirable properties [1,2] . It was found that adding modifier is the most popular and effective method to refine the primary silicon [3][4][5] . The effective refinement of primary Si can be obtained through the addition of some modifiers, such as P [4][5][6] , rare earth (RE) [7,8] , etc. However, the use of P can result in serious air pollution, and the costly RE used to refine primary Si is poor effective. So, researchers have been looking for new and more efficient and effective modification agents for Al-Si casting alloys.According to research [9] , Al-ZnS master alloy was used as a new refiner, and the primary silicon could be refined from more than 80 μm to 20 μm. Fan et al. also researched the modification performance of ZnS on primary Si in hypereutectic Al-Si alloy and came to the same conclusion [10] , in which ZnS was synthesized by chemical reaction using Zn and Na 2 S. Nevertheless, Abstract: A new modifying agent, ZnS, was used as a refiner to modify primary silicon in hypereutectic AlSi alloy. The factors affecting the modification results, including addition level of ZnS and holding time, were investigated. The results showed that the average size of the most effectively modified primary silicon was 28.5 μm when the ZnS mixed powder addition was 0.15wt.% with a holding time of 10 min. More important, the average size of primary silicon could remain below 40 μm despite the holding time extending to 120 min, which means ZnS is a promising modifying agent of primary Si in industrial applications. Na 2 S is so deliquescent in the air that it is not favorable for storage. The ZnS synthesized by direct chemical reaction of Zn and S can be stored trouble-free, and the yield was very high, but research concerning the refinement and modification behavior of ZnS on Al-Si alloy hardly can be found. To investigate the recession degree of ZnS modification synthesized by Zn and S and the optimal addition level, the effects of ZnS addition amount and holding time on Al-Si alloy were investigated. Key words: Experimental procedureAccording to the study of hypereutectic Al-Si alloy, the shrinkage of Al-Si alloy was the lowest when the content of silicon was between 22wt.%-25wt.% [11] .Therefore, Al-24wt.% Si alloy was chosen to be the base alloy in this study. Figure 1 shows the microstructure of Al-24Si alloy without ZnS addition. Primary silicon particles exhibit coarse irregular and star-shaped morphologies in the as-cast alloy, which will drastically degrade the mechanical properties of the castings, and the average size of primary Si is up to abo...

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confidence: 99%

Effects of ZnS modification on primary Si in hypereutectic Al-Si alloy

Sun

Si³

et al. 2017

China Foundry

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“…The complete equilibrium solidification involves the five successive phase fields denoted in Figure 13, and during that process, the alloy releases the total heat ⌬H total between liquidus (T l ) and solidus (T s ) temperature: [6] One possibility to calculate a latent heat is to supercool the liquid down to T s , using the known heat capacity of the liquid, and then to solidify isothermally at T s to the equilibrium phases, resulting in a latent heat: [7] Another possibility is to solidify the liquid at T l to the superheated solid phases, which are subsequently cooled to T s , resulting in a different latent heat: [8] Even though the first path suggested in Eq. [6] may appear more natural, it is in no way unique.…”

Section: Thermodynamic Calculationmentioning

confidence: 99%

“…In a hypereutectic Al-21Si alloy, Chang et al [7] observed simultaneous refinement of both primary and eutectic Si using RE mischmetal additions. The concentration of RE in primary (Si) and the enriched matrix was also studied by Chang et al [8] and the few earlier reports on the effect of RE additions are reviewed. [7,9] However, the actual grain refining mechanisms are still unclear.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic aspects of the constitution, grain refining, and solidification enthalpies of Al-Ce-Si alloys

Gröbner

Mirković

Schmid–Fetzer

2004

Metall Mater Trans A

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The ternary Al-Ce-Si phase equilibria were investigated using X-ray diffraction (XRD) methods, metallography, scanning electron microscopy with energy-dispersive X-ray analysis (SEM/EDX) and wavelength-dispersive X-ray microanalysis, and differential thermal analysis (DTA). The focus was on the Al-rich corner and the phases in equilibrium with (Al). Key experiments were selected by preliminary thermodynamic calculations. A consistent thermodynamic description was developed using the Calphad method incorporating all experimental data. A thermodynamic assessment for the binary Ce-Si system was also performed. Two ternary phases, Ce(Si 1Ϫx Al x ) 2 ( 1 ) and AlCeSi 2 ( 2 ), were confirmed. The phase Al 2 CeSi 2 ( 4 ) was sporadically observed, but is apparently metastable. The earlier reported phase Al 4 Ce 3 Si 6 could not be confirmed. In addition, the enthalpy of solidification of five Al-rich ternary alloys was measured in a differential scanning calorimetry (DSC) heat flux calorimeter. The agreement with the thermodynamic enthalpy calculations is acceptable. The fundamental intricacies involved in calculating a "latent" heat for alloys with a freezing range are pointed out. Various phase diagrams of the Al-Ce-Si system were calculated based on the thermodynamic description. They were used to quantitatively identify possible contributions to the grain refinement potential of Ce in Al-Si alloys due to the phase equilibria.

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“…In addition, rare-earth elements and Sc refine grain size, thereby improving the strength and corrosion resistance of Al-alloys [4,5]. Ce and La in misch metal are the other useful elements, which can be used to refine the grain size [6]. From the results of other studies [4,6], it is speculated that Al-Mg-Sc-Mm alloy is a potentially high performance Al-alloy.…”

Section: Introductionmentioning

confidence: 99%

“…Ce and La in misch metal are the other useful elements, which can be used to refine the grain size [6]. From the results of other studies [4,6], it is speculated that Al-Mg-Sc-Mm alloy is a potentially high performance Al-alloy. Therefore, we investigated the mechanical behavior of as-cast Al-4Mg-0.45Sc-0.5Mm alloy by performing tensile tests at room temperature and at different strain rates.…”

Section: Introductionmentioning

confidence: 99%

Tensile behavior of Al−4%Mg−0.4%Sc−0.5% misch metal alloy at room temperature

Woo

Kim

2005

Met. Mater. Int.

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The effects of strain rate and pre-deformation in Al-4 wt.%Mg-0.4 wt.%Sc-0.5 wt.%Mm (misch metal) alloy on tensile behavior and P-L effect have been investigated. Pre-deformation of Al-4 wt.%Mg-0.4 wt.%Sc-0.5 wt.%Mm alloy clearly enhances the yield strength and ultimate strength, though it decreases the fracture strain. The yield strength of pre-deformed Al-4 wt.%Mg-0.4 wt.%Sc-0.5 wt.%Mm alloy is higher than that of commercially used Al-Mg based alloys. The strength of Al-4 wt.%Mg-0.4 wt.%Sc-0.5 wt.%Mm alloy was changed slightly at a strain rate between 2×10 5 s 1 and 2×10 3 s 1 , but changed significantly when predeformation was introduced. Tensile test results of as-cast Al-4 wt.%Mg-0.4 wt.%Sc-0.5 wt.%Mm alloy show a significant oscillation of serration during deformation at room temperature, and the critical strain (H c ), which is the strain at the start of serration, decreases with increasing strain rate. Pre-deformation of Al-4wt%Mg-0.4wt%Sc-0.5wt%Mm also affects the serration oscillation: it decreases the critical strain at lower strain rate and increases it at higher strain rate (>2×10 4 s 1 ).

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Rare earth concentration in the primary Si crystal in rare earth added Al-21wt.%Si alloy

Cited by 90 publications

References 8 publications

Effects of ZnS modification on primary Si in hypereutectic Al-Si alloy

Effects of ZnS modification on primary Si in hypereutectic Al-Si alloy

Thermodynamic aspects of the constitution, grain refining, and solidification enthalpies of Al-Ce-Si alloys

Tensile behavior of Al−4%Mg−0.4%Sc−0.5% misch metal alloy at room temperature

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