Surface tension of binary and ternary aluminium alloys of the systems Al-Si-Mg and Al-Zn-Mg

Goicoechea, J.; García‐Cordovilla, C.; Louis, E.; Pamies, A.

doi:10.1007/bf02403824

Cited by 54 publications

(12 citation statements)

References 12 publications

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“…Although the data on these effects are very limited, some data for the variation of the surface tension of liquid aluminum with temperature and solute content are available. [7][8][9] As noted earlier, the Marangoni convective flow is also along the maximum temperature gradient and hence parallel to the columnar grain boundaries. This is significant in scavenging the solute rejected by the growing dendrite arms and moving it down into the roots of the columnar boundaries, thereby increasing the local segregation and the freezing range of the alloy, and so its propensity to permit void nucleation and the creation of a hot tear.…”

Section: Introductionmentioning

confidence: 58%

The Influence of Marangoni Flows on Crack Growth in Cast Metals

Yang

Smith

Saho

et al. 2002

Annals of the New York Academy of Sciences

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In previous work with copper-based alloys, the authors showed that a necessary part of the hot-tearing process is the creation of a void in association with an inclusion and its subsequent growth to form the crack observed in the as-cast state. The work reported here is an examination of hot tearing in aluminum alloy A201 and various similar Al-based aerospace alloys to determine (1) if a similar process to that seen in copper alloys takes place; (2) the extent to which buoyancy forces influence the movement of solute-enriched liquid and so contribute to the development of voids which are subsequently observed as hot tears; and (3) the influence of the local variations in liquid/void surface tension arising due to local composition and temperature changes on interdendritic fluid flow--that is, the effects of Marangoni convection on void size and movement during solidification. Hot cracking of aluminum alloy A201 has been examined under standardized experimental conditions. In addition, experiments were conducted in which fluid flow in test castings was controlled by magnetic fields. The results from these various investigations are presented in this paper. Similar experiments are planned for reduced gravity aircraft parabolic flights. To assist in the planning and interpretation of the results, numerical modeling simulations have been developed for Al-Cu alloys.

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Section: Introductionmentioning

confidence: 58%

The Influence of Marangoni Flows on Crack Growth in Cast Metals

Yang

Smith

Saho

et al. 2002

Annals of the New York Academy of Sciences

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“…Considering that the infiltration rate is a function of the viscosity and surface tension of the liquid metal, Mg is capable of reducing both properties, leading to an improved motion of liquid into the porous network which in turn increases the fluidity of the molten metal. [10] The surface tension reduction is very sharp for the initial 1 wt.% Mg addition (from 860 mN/m to 650 mN/m). With further addition of Mg the reduction is very marginal.…”

Section: Processing and Characterization Of Al-cu And Al-mg Basementioning

confidence: 94%

Processing and Characterization of Al‐Cu and Al‐Mg Base Composites Reinforced with TiC

Contreras¹,

Albiter²,

Bedolla³

et al. 2004

Adv Eng Mater

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elements will contain diamond cutting plates since preliminary studies carried out at MTU Aero Engines proofed that this material shows practically no attrition when cutting the fibers.Laser cutting does not lead to a proper cutting surface. This process is therefore not suitable for further application. Together with laser cutting a so called ªonion-structureº was observed on the pyrolithic carbon coating of SiC fibers, which leads additionally to a fiber destruction at the interface SiC to Titanium coating. Two possible explanations can be given for this effect. Either it is due to a reaction between the Titanium 6±4 and the pyrolithic graphite layer or due to the destruction of bonds between the atomic layers of graphite as a result of heat influence.Conclusions: This paper described different cutting methods for SiC fibers (bending, scissors cutting and laser cutting) and evaluated the results. The laser cutting method is not suitable due to the change in fiber morphology at the cut surfaces and the destruction of the pyrolithic graphite interlayer. Scissors cutting of fibers is problematic as well. The two scissor blades penetrate the fiber and generate a complex stress field, which may lead to chip fractures with undesirable particle contamination. According to the evaluated results cutting by bending is the best method. The fracture is plane and perpendicular to the fiber axis, producing a smooth fracture surface at a predictable location without particles. ExperimentalUncoated and coated SiC fibers were cut by a CO 2 laser. The laser RS500/ 700 was supplied by ROFIN-SINAR Hamburg, Germany.For cutting two plates on which the fibers were fixed with adhesive tapes were prepared. These plates were separated by a distance of 2,5 cm. At the point equidistant from both plates, the laser cut into the fibers.The laser used had a focal distance of 1000 lm. Since the diameter of the fibers is about 140 lm and due to the fact that the laser lens focus could be moved only in steps of 100 lm, a distance of the fiber surface to the laser lens of 900 lm was selected. This way the focus of the laser was about 40 lm within the fiber itself. Laser power was increased in steps of 10 W starting at 0 W and ending at 260 W or 290 W for the coated and uncoated SiC fibers respectively.All of the presented electron microscope scans were obtained by means of an SEM CamScan S2, Cambridge, UK equipped with an energy dispersive microanalyser (EDX, Edwin M-series, Röntec, Berlin, Germany).The cutting depths of the coated and uncoated SiC fibers were determined by means of MS Picture Publisher .Metal matrix composites (MMCs) reinforced with ceramic particles offer high strength and high values of the elastic modulus as well as good high-temperature properties compared to the corresponding monolithic materials used as the matrix. [1] The nature of the technique used in the fabrication of MMCs has a significant effect on the overall properties of the product. In the case of the liquid-metal processing of composites, a major difficulty fo...

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“…Here, γ is the surface tension of the liquid and r is the radius of the microbubble. Although the surface tension of aluminium varies with oxygen content, alloying elements and temperature [31][32], we use γ of pure liquid aluminium, which at 660 °C is about 1 Nm -1 [33]. Accordingly, ∆p for a spherical microbubble of radius 10 µm is 2 bar, whereas ∆p for a spherical bubble of radius 1 mm is only 0.02 bar.…”

Section: Evolution Of Microporosity In Liquid Foammentioning

confidence: 99%