Papers by Keyword: Liquid Metal

Abstract: The dynamics of ultrasonic bubbles in liquid metal are captured in-situ for the first time using the ultrafast X-ray phase contrast imaging facility housed at the Advanced Photon Source, Argonne National Laboratory, in the USA. The experimental observations are complemented by the simulations of the acoustic pressure field, the bubble diameter oscillation and the associated pressure and velocity pulses at the bubble wall due to the alternating pressure wave. The experiment and simulation agree well and provide more quantitative insight into the understanding of the highly transient behaviour of the ultrasonic bubbles and their interaction with the surrounding liquid metal.

Abstract: Lotus-type porous structure is a new kind of micro-channel structure and can be used as heat sink for heat elimination of high powered electronic devices. Numerical analysis based on the simple fin model was used to predict the equivalent heat transfer coefficient of lotus-type porous copper micro-channel heat sink. Compared with the water, GaInSn working fluid could further promote the heat transfer performance of the heat sink. According to the theoretical analysis, a heat transfer coefficient as high as 14W/(cm²K) was attainable when the pressure drop was 50 KPa and an appropriate structure parameters: 0.4 mm in pore diameter, 0.4 in porosity and 4mm in height of porous copper were achieved.

Abstract: Liquid metal flowing through filter media can create a vacuum in channel. Inclusions and gases in liquid metal are adsorbed onto surface of the filter media by negative pressure so that liquid metal was purified. Theoretical discussion was carried on the use of vacuum to purify metal and a series of measures such as increasing casting speed were proposed to improve the effect of purification. Experiments show that these measures are effective.

Abstract: The soft cobbing, used in steel’s continuous casting, is widely applying in technologies of rolled metal manufacturing. It is important to know ingot’s stress-strain state and dynamics of ingot’s changes while cobbing, when there is a liquid metal in the centre of section. The complex questions of numerical modeling of soft cobbing process and experimental investigation on physics plasticine models are considered in presented work. The analysis of findings is presented in the article.

Abstract: Melt quality is crucial for both continuous and shape casting of light alloys. Gas, oxides and other inclusions in the melt usually deteriorate the quality of the casting products. Conventional refining techniques, such as filtration and rotary degassing, can refine the melt by removing the inclusions although they are costly and time-consuming. A new technology for liquid metal treatment through intensive melt shearing was developed recently to improve the melt quality prior to metal casting. The new technology uses a simple rotor-stator unit to provide intensive melt shearing, which disperses effectively the harmful inclusions into fine particles to enhance nucleation during the subsequent solidification processing. Experimental results have demonstrated that the high shear unit can be used for general melt treatment, physical grain refinement, degassing and preparation of metal matrix composites and semisolid slurries. In this paper we offer an overview of the high shear device and its application in processing light alloys.

Abstract: A lead-free hypoeutectic solder Sn-0.3Ag-0.68Cu-X with low sliver content was prepared by a new process. By the method of skimming surface oxidation film at static state, the growing behaviors of oxidation film on the surface of liquid solder alloy were studied. The experimental results show that the growth rate of oxidation film on the surface of liquid solder decreases greatly after surface modification process. Before the surface modification process, the growth behaviors of oxidation film on the surface of liquid solder obey parabolic law which changes with variation of time. After surface modification, the growth behavior of oxidation film of liquid solder is transformed into obeying logarithmic law. The formation rate of oxidation slag on the surface of liquid Sn-0.3Ag-0.68Cu-X solder can be reduced to 0.36 mg/cm².min at 260 °C under standard test conditions. Conceptually, the atomic-doping X (X=Ga, In, Bi, Ge, Sb, Ni and P) was absorbed to the surface of liquid solder according to Gibbs absorption equation and entered into oxidation film, which is prone to form more compact oxidation film to prevent the oxidation on the surface of liquid solder.

Abstract: The ultra high temperature performance of ceramic-based complex structures may require the development of liquid-assisted joining techniques; this in turn requires the definition of the wettability of these materials by various metals over a wide range of compositions and temperatures. After a short description of the relevant experimental aspects of wettability studies at high temperatures, a discussion is presented on how these results can be used to derive chemical and structural information on the solid-liquid interactions. Reference is made mainly to metal-ceramic systems; a summary of the results of sessile drop tests under carefully controlled conditions is given in relation to the wettability and the interfacial characteristics of systems based on transition metals (Zr, Hf) diboride ceramics in contact with liquid Ag, Cu, Au and Ni and of some of their alloys with Ti, Zr, Hf and B to promote/control wettability. In particular, the utilization of phase diagrams is discussed, as one of the most powerful tool to design the filler alloy compositions for the optimization of joining (brazing) processes.

Abstract: The glass fluxing technique was used to undercool melts of pure Cu and Ge in the presence of a static magnetic field generated by a superconducting magnet. It was found that the mean undercooling of liquid Cu increased with increasing magnetic field, whereas the mean undercooling of liquid Ge did not show any significant changes with increasing magnetic field. Such a difference in the undercooling behavior can be related to the Lorentz force imposed by the magnetic field, which was larger for liquid Cu because of a larger electrical conductivity than that of liquid Ge.

Abstract: There are a number of well-known empirical relations for diffusion in solids. For example the proportionality between the self-diffusion activation energy and melting point or between the entropy of the diffusion and the ratio of activation energy and the melting point (Zener rule) are perhaps the best known ‘rules of thumb’. We have shown earlier in our Laboratory, that these relations are direct consequences of the similarity of interatomic potentials seen by ions in solids. On the basis of this, similar relations were extended for impurity and self diffusion in binary solid alloys. In this paper, results for binary liquid mixtures will be reviewed. First a minimum derivation of the temperature dependence of the self-diffusion coefficient, D, is presented (minimum derivation in the sense that it states only that the reduced (dimensionless) D should be a universal function of the reduced temperature), using the similarity of interatomic potentials and dimensional analysis. Then the extension of this relation for determination of the pressure and composition dependence of the self-diffusion coefficients is described using pressure and composition dependent scaling parameters (melting point, atomic volume and mass). The obtained universal form (valid for binary liquid alloys) is very useful for the estimation of the temperature, composition and pressure dependence of the self-diffusion coefficients. Finally, the relation for the ratio of the impurity and self-diffusion coefficients is derived.

Abstract: Planning for a U.S. test blanket module to operate in the internationally-sponsored ITER reactor has focused attention on the many coating and compatibility issues that will need to be solved before fusion energy moves from concept to commercial reality. Examples are given for (1) a dual-layer, electrically-resistant coating as a potential solution to reduce the magnetohydrodynamic pressure drop with liquid Li and (2) materials compatibility issues with eutectic Pb-Li for conventional alloys and SiC/SiC composites. Because of the reduced activity of Li in Pb-Li, a wider range of functional materials can be considered in this system. Nevertheless, an Al2O3 scale on FeCrAl was transformed to LiAlO2 after exposure to Pb-Li at 800°C.