Silicon morphology modification in the eutectic Al–Si alloy using mechanical mold vibration

Abu-Dheir, Numan; Khraisheh, Marwan; Saito, Kozo; Male, Alan T.

doi:10.1016/j.msea.2004.09.038

Cited by 102 publications

(92 citation statements)

References 26 publications

(27 reference statements)

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“…Fine equiaxed microstructures generally reveal favourable mechanical properties in terms of strength and ductility, with low susceptibility to microporosity and cracks. 3 The microstructure is characterized by various parameters such as the grain size, the dendrite arm spacing (DAS), the size, shape and distribution of the eutectic silicon particles, as well as the morphologies and the amounts of intermetallic phases present. 1 One of the main melt treatment processes applied to Al-Si alloys is modification where, by the addition of a controlled amount of sodium (Na) or strontium (Sr), the eutectic Si morphology is 'modified' i.e., changed from acicular or needle-like to a fine, fibrous form (spheroidized), in order to improve the alloy properties.…”

Section: IXmentioning

confidence: 99%

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effet de l'addition du "michmetal", du taux de refroidissement et du traitement thermique sur la microstructure et la dureté des alliages Al-Si de type 319, 356, et 413 /

Sebaie¹

2006

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Aluminum cast components have been widely used in many applications for over the past twenty years. The demands made by the transportation industry for light weight components (in order to reduce fuel consumption) has led to an increased use of aluminum alloys in the production of a wide variety of castings including critical components such as engine blocks and cylinderheads. Among these, Al-Si alloys are the most popular commercial alloys used for these applications, due to their high strength-to-weight ratio, high tensile and fatigue properties, and excellent corrosion and wear resistance. The addition of Si provides excellent castability and high resistance to hot-tearing, while the presence of alloying elements such as magnesium and copper offer the ability to heat treat Al-Si castings to high strength levels, which make them suitable for the production of highstress components for the automotive, aircraft and defense industries.The mechanical properties of a casting are controlled by its microstructure which, in turn, is influenced by the chemical composition of the alloy, i.e., by its Si, Mg, and Cu content, and by the presence of impurities such as iron, the presence of casting defects (porosity, inclusions, etc.), as well as the solidification conditions (i.e., cooling rate) and heat treatment applied. In the case of Al-Si alloys, this would imply the a-Al dendrite arm spacing (DAS), the morphology and size of the eutectic Si particles, and the amount of intermetallics and/or other second-phase constituents present in the microstructure.Cooling rate, in general, controls the fineness of the microstructure: the higher the cooling rate, the finer the a-Al dendrites and other phase particles, and the smaller the dendrite arm spacing.hi Al-Si alloys, the eutectic Si particle characteristics (i.e., size, morphology and distribution) are known to appreciably affect the mechanical properties. In the as-cast condition, the eutectic Si is observed in the form of brittle acicular plates that are detrimental to the tensile and impact properties. Through the use of a melt treatment termed "modification", the morphology of the eutectic Si is altered or "modified" from its acicular form to a fine, fibrous form that significantly improves the alloy ductility (and strength). The modification is carried out through the addition of elements such as Na, Sr, Ca, or mischmetal (a mixture of rare earth metals).The use of Na and Sr as modifying agents for Al-Si alloys is well established. Recently, however, interest has been focused on the use of mischmetal as a modifier for these alloys. Mischmetal is a combination of rare earth metals (Ce, La, Pr and Nd), and has been reported to act as a Si particle modifier in Al-Si alloys, with the capacity to overcome the problems of hydrogen pick-up, increased porosity and fading associated with the use of Vil strontium. Mischmetal has also been reported to have a high chemical reactivity with Al, Si, Cu and Mg, giving rise to the formation of hard, high melting-point intermeta...

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Section: IXmentioning

confidence: 99%

“…A high strength-weight ratio is one of their most interesting characteristics. Aluminum has a density of only 2.7 g/cm 3 , approximately one third that of steel. As the density of silicon is 2.3 g/cm 3 , it is one of the few elements which may be added to aluminum without loss of weight advantage.…”

Section: Introductionmentioning

confidence: 99%

effet de l'addition du "michmetal", du taux de refroidissement et du traitement thermique sur la microstructure et la dureté des alliages Al-Si de type 319, 356, et 413 /

Sebaie¹

2006

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“…Poor ductility was found in microstructures solidified at low cooling rates (>1 °C/s) that showed an overgrowth of primary Si in the Al matrix, as well as a large fraction of coarse acicular eutectic Si. On the other hand, rapid cooling may produce fragility in thin-section castings 9 . In order to minimize the above-mentioned problems and to improve the mechanical properties, several solutions such as addition of alloying elements, control of the solidification rates and performing different heat treatments have been proposed 10 .…”

Section: Introductionmentioning

confidence: 99%

Study of the Al-Si-X system by different cooling rates and heat treatment

et al. 2012

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The solidification behavior of the Al-12.6% Si (A1), the hypereutectic Al-20%Si (A2) and the Al-20%Si-1.5% Fe-0.5%Mn (A3) (in wt. (%)) alloys, at different cooling rates is reported and discussed. The cooling rates ranged between 0.93 °C/s and 190 °C/s when cast in sand and copper wedge-shaped molds, respectively. A spheroidization heat treatment was carried out to the alloys in the as-cast condition at 540 °C for 11 hours and quench in water with a subsequent heat treatment at 170 °C for 5 hours with the purpose of improving the mechanical properties. The samples were characterized by optical microscopy, scanning electron microscopy and mechanically by tensile test, in order to evaluate the response of the heat treatment on the different starting microstructures and mechanical properties. It was found that alloys cooled at rates greater than 10.8 °C/s had a smaller particle size and better distribution, also showed a greater response to spheroidization heat treatment of all silicon (Si) phases. The spheroidization heat treatment caused an increase in the ultimate tensile stress (UTS) and elongation when compared with the alloys in the as-cast condition. The highest UTS value of 174 MPa was obtained for the (A1) alloy.

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“…In the casting process accompanied solidification phenomenon, rapid cooling, [3][4][5][6] addition of refiners, [7][8][9][10][11][12] application of vibrations, [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] etc. are considered as a structural refinement method.…”

Section: Introductionmentioning

confidence: 99%

“…In contrast, the application of vibrations is able to refine microstructure even in bulk materials without a refiner. Mechanical vibration, such as mechanical mold vibration 13,14) or ultrasonic vibration, [15][16][17][18][19] and electromagnetic vibrations [20][21][22][23][24][25][26][27][28][29][30][31][32] are considered as an imposition method of vibrations. The application of mechanical vibrations such as ultrasonic ones enables not only refinement of the crystal grain, but also uniform dispersion of inclusion materials, degassing, improvement of metal feeding, etc.…”

Section: Introductionmentioning

confidence: 99%

Effect of Electromagnetic Vibration Frequency and Temperature Gradient on Grain Refinement of Pure Aluminum

2007

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The electromagnetic vibrations are applied to grain refinement of pure aluminum (99.7 mass%) and the effects of electromagnetic vibration frequency and temperature gradient on grain refinement are investigated. As the pure aluminum melt has been subjected to electromagnetic vibrations with a frequency range from 150 to 500 Hz, crystal grain has become small with increase of vibration frequency. To the contrary, the effect of refinement has become weak at the vibration frequency more than 1 kHz and this microstructure is similar to one of nonvibrated state. When the longitudinal temperature gradient in the specimen becomes gradual, refined area is remarkably extends. It is assumed that refinement by the electromagnetic vibrations is significantly affected by the temperature gradient.

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Silicon morphology modification in the eutectic Al–Si alloy using mechanical mold vibration

Cited by 102 publications

References 26 publications

effet de l'addition du "michmetal", du taux de refroidissement et du traitement thermique sur la microstructure et la dureté des alliages Al-Si de type 319, 356, et 413 /

effet de l'addition du "michmetal", du taux de refroidissement et du traitement thermique sur la microstructure et la dureté des alliages Al-Si de type 319, 356, et 413 /

Study of the Al-Si-X system by different cooling rates and heat treatment

Effect of Electromagnetic Vibration Frequency and Temperature Gradient on Grain Refinement of Pure Aluminum

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