Effects of cobalt content on microstructure and mechanical properties of hypereutectic Al–Si alloys

Sha, Meng; Wu, Shusen; Wang, Xingtao; Wan, Li; An, Ping

doi:10.1016/j.msea.2011.12.077

Cited by 35 publications

(12 citation statements)

References 8 publications

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“…It can be seen that Ṫ decreased with the progress of solidification from the cooled bottom of the casting due to two reasons: 1) The continuous growth from bottom to top of the casting increases progressively the thermal resistance of the solid layer; [ 32 ] 2) the thermal and volumetric shrinkage accompanying the solidification of the casting generates an increasing gap between the casting and the mold wall, thus inducing an interfacial thermal resistance that increases over time. [ 33,34 ] In previous studies, [ 35–39 ] the fishbone morphology was reported to be dependent on Ṫ and V and on the composition of the alloy. Particularly, high cooling rates and increase in a specific solute content promoted the formation of fishbone intermetallic particles.…”

Section: Resultsmentioning

confidence: 99%

“…Even the morphological transition of the Al 3 Ni IMCs from plate‐like to fishbone was not able to contribute to improvement in ductility. Sha et al [ 39 ] attributed to the Al 9 (Fe,Co,Ni) 2 IMCs with fishbone morphologies the brittleness of Al–Si hypereutectic alloys, but these intermetallics were coarse and had a sharp edge aspect, acting as stress concentrators. On the other hand, Yang et al [ 38 ] reported improvement in elongation when the needle‐like β‐AlFeSi IMCs were replaced with α‐Al(Fe,Cr)Si IMCs having a fishbone morphology.…”

Section: Resultsmentioning

confidence: 99%

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Morphology of Intermetallics Tailoring Tensile Properties and Quality Index of a Eutectic Al–Si–Ni Alloy

2020

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The Al-Si-Ni alloy system is a source of multicomponent piston alloys, which combine good castability and wear resistance of Al-Si alloys with great thermal stability and corrosion resistance of Al-Ni alloys. [1-3] The inherent high piston temperature during engine functioning is one of the limiting factors for the application of Al-Si-based alloys. [4] On the other hand, alloys containing Al-Ni-based intermetallic compounds (IMCs) are mainly used for high-temperature structural products, which also demand wear resistance, such as aircraft engines, turbine vanes, and guide vanes of industrial steam turbines. [5,6] The formation of Ni-rich IMCs occurs even for low Ni concentrations, [7] as Ni is almost insoluble in aluminum, with a solubility of about 0.05 wt% at 640 ºC and less than 0.005 wt% at 450 ºC. [8] Thus, the addition of Ni to Al─Si alloys can potentially improve their wear resistance at elevated temperatures. Once the second phases are responsible for these characteristics, the modification of the microstructure, regarding its refinement, usually improves the properties and extends the lifetime of the component. Apart from the formation of different IMCs, the addition of new alloying elements can promote modification of other phases, mainly on Si. Kaya and Aker [9] studied ternary Al-12.6 wt% Si-2 wt% X alloys, where X was Cu, Co, Ni, Sb, or Bi. They verified that the addition of Co promotes a better distribution of Si flakes (i.e., smallest interflake spacings) and, consequently, highest hardness and tensile strength are achieved. Although the addition of Cu induced the least efficient refinement effect, the Al-12.6 wt% Si-2 wt% Cu alloy showed the second highest tensile properties. This occurred probably due to the formation of a supersaturated solid solution and hard Al 2 Cu particles. As Al 2 Cu and Al 9 Co 2 have similar hardness (588 [10] and 568 HV, [11] respectively), and Co is restricted to the formation of Al 9 Co 2 , the refinement of Si seems to have a major effect on mechanical properties. The aforementioned alloying elements are not modifiers of the eutectic Si morphology, but they just decrease the interflake spacing. Sr is a strong modifier, which is capable of transforming the acicular Si in welldistributed fibers with only a few hundred parts per million. In an Al-10 wt% Si alloy, 240 ppm of Sr has the same effect as 520 ppm of Ti-B grain refiner in terms of tensile properties. [12] Another Si modifier, Sc, also decreases the secondary dendritic arm spacing and refines the grain size; however, it requires an amount 20 times greater than that of Sr to improve the mechanical properties at the same level. [13] In secondary aluminum, Mn, [14,15] Cr, [16,17] Ni, [18,19] and other alloying elements are added to suppress the precipitation of harmful β-AlFeSi, aiming at the formation of α-AlFeSi, which has a Chinese-script morphology. Even though modification is, in general, desirable, excessive addition can lead to overmodification. Riestra et al. [20] observed in Al-11 wt% Mg 2 Si alloys, in ...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Morphology of Intermetallics Tailoring Tensile Properties and Quality Index of a Eutectic Al–Si–Ni Alloy

2020

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“…Modifiers are added to the alloy in purpose of refinement of Si particles (primary and eutectic) as well as better and more homogenous distribution of particles. In case that there is iron present in the alloy it acts like impurity reducing wear rate, but with addition of Manganese it is possible to null the effect of iron on the alloy and increase wear rate [10][11][12][13][14]. As a modifier in hypereutectic alloys was even used Calcium in [15].…”

Section: Introductionmentioning

confidence: 99%

A review of hypereutectic aluminum piston materials

Miladinović

Stojаnović

Gajević

et al. 2022

IOP Conf. Ser.: Mater. Sci. Eng.

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Demands of today’s automotive industry are increasing; there is a constant tendency of weight reduction and higher reliability of constructions. Pistons and piston liners for vehicles are mostly manufactured from aluminum-silicon alloys. With different manufacturing methods and/or the addition of some chemical elements, base alloy properties can be modified. Methods for hypereutectic aluminum alloys and composites manufacturing and their influence on material properties will be given in this paper. The influence of Si percentage in base alloy and how an addition of some chemical elements affects the properties of these materials will be observed as well.

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“…Their morphology was mainly transformed from long acicular phases to Chinese script, granular, or rod-like Fe-containing phases resulting in the improvement of the tensile strength at room and elevated temperature. Some literature has been published on the mechanical properties of Co modification for Fe-containing Al-Si-based alloys [ 26 , 27 ]. No studies have yet shown a relationship between electrical/thermal conductivities, mechanical properties, and the microstructure of near-eutectic Al-2Fe alloys with different Co contents.…”

Section: Introductionmentioning

confidence: 99%

Microstructures and Mechanical Properties of Al-2Fe-xCo Ternary Alloys with High Thermal Conductivity

Luo

Huang

et al. 2020

Materials

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The microstructures, mechanical properties, and thermal conductivity (TC) of Al-2Fe-xCo (x = 0~0.8) alloys in as-cast, homogeneous annealed, and cool rolled states are systematically studied. Results indicate that appropriate Co modification (x ≤ 0.5) simultaneously improves the thermal and mechanical properties of as-cast Al-2Fe alloys. The improvement of TC is attributed to ameliorating the morphology of primary Al3Fe phases from needles to short rods and fine particles, which decreases the scattering probability of free electrons during the electronic transmission. However, further increasing the Co content (x = 0.8) decreases the TC due to the formation of a coarse plate-like Al2FeCo phase. Besides, the thermal conductivity of annealed Al-2Fe-xCo alloys is higher than that of as-cast alloys because of the elimination of lattice defects and spheroidization of Al3Fe phases. After cool rolling with 80 % deformation, thermal conductivity of alloys slightly increases due to the breaking down of Al2FeCo phases. The rolled Al-2Fe-0.3Co alloy exhibits the highest thermal conductivity, which is about 225 W/(m·K), approximately 11 % higher than the as-cast Al-2Fe sample. The ultimate tensile strength (UTS) and elongation (EL) of as-cast Al-2Fe-0.5Co (UTS: 138 MPa; EL: 22.0 %) are increased by 35 % and 69 %, respectively, compared with those of unmodified alloy (UTS: 102 MPa; EL: 13.0 %).

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Effects of cobalt content on microstructure and mechanical properties of hypereutectic Al–Si alloys

Cited by 35 publications

References 8 publications

Morphology of Intermetallics Tailoring Tensile Properties and Quality Index of a Eutectic Al–Si–Ni Alloy

Morphology of Intermetallics Tailoring Tensile Properties and Quality Index of a Eutectic Al–Si–Ni Alloy

A review of hypereutectic aluminum piston materials

Microstructures and Mechanical Properties of Al-2Fe-xCo Ternary Alloys with High Thermal Conductivity

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