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Aluminum-Copper Alloys

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Srinath Viswanathan – One of the best experts on this subject based on the ideXlab platform.

  • Permeability measurements of the flow of interdendritic liquid in equiaxed aluminum-silicon Alloys
    Metallurgical and Materials Transactions B, 2003
    Co-Authors: Qingyou Han, Srinath Viswanathan, A. J. Duncan

    Abstract:

    A method developed recently for measuring instantaneous permeability in the mushy zone of Aluminum-Copper Alloys is used to measure permeability in aluminum-silicon Alloys. Permeability was also measured in packed glass beads using water, because measurements could be conducted in the absence of microstructural coarsening. Experimental data are compared with the Kozeny-Carman equation to determine the value of k _ C , the Kozeny-Carman constant. The results indicate that when k _ C =5.0, all the instantaneous permeability data agree well with the Kozeny-Carman equation. Factors affecting the accuracy of permeability measurements, such as surface oxidation of the sample, flow channeling during the test, microstructural coarsening, and liquid fraction reduction due to back diffusion in the solid are discussed. An experimental technique that minimizes errors due to these factors is outlined.

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  • Liquid Permeability Measurements in Solidifying Aluminum-Copper Alloys
    , 1999
    Co-Authors: A. J. Duncan, Qingyou Han, Srinath Viswanathan

    Abstract:

    Measurements of liquid permeability in the mushy zones of AI-15.42% Cu and Al-8.68% Cu alloy samples have been performed isothermally just above the eutectic temperature, using eutectic liquid as the fluid. A modified method has been developed to determine the specific permeability, K{sub s}, as a function of time during the test from the data collected on these Alloys. Factors affecting permeability measurements are discussed. Permeabilities are observed to vary throughout the experiment. This is attributed to microstructural coarsening and channeling that occurs in the sample during the experiment. The permeability is related to the microstructure of the sample using the Kozeny-Carman equation. The correlation between the measured K{sub s}, liquid fraction, g{sub L} and the specific solid surface area, S{sub v}, improves markedly when compared to previous studies in which microstructural coarsening was ignored.

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  • Measurement of Liquid Permeability in the Mushy Zones of Aluminum-Copper Alloys
    Metallurgical and Materials Transactions B, 1999
    Co-Authors: A. J. Duncan, Qingyou Han, Srinath Viswanathan

    Abstract:

    Measurements of liquid permeability in the mushy zones of Al-15.42 pct Cu and Al-8.68 pct Cu alloy samples were performed isothermally just above the eutectic temperature, using eutectic liquid as the fluid. A modified method was developed to determine the specific permeability as a function of time (K
    s) during the test from the data collected on these Alloys. Factors affecting permeability measurements are discussed. The permeabilities are observed to vary throughout the experiment. This is attributed to microstructural coarsening and channeling that occur in the sample during the experiment. Coarsening rates are determined for the isothermal coarsening tests without fluid flow, and the results are observed to be less than the rates indicated from permeability tests where fluid flow is present. Careful measurement of the volume fraction of liquid (g
    L) shows that g
    L decreases during the test. The permeability is then related to the microstructure of the sample using the Kozeny-Carman equation. The correlation between the measured K
    S, g
    L, and specific solid surface area (S
    V) improves markedly when compared to previous studies, when microstructural parameters at the initial stage of the test are used.

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A V Larin – One of the best experts on this subject based on the ideXlab platform.

  • mechanisms and rate of dislocation nucleation in aluminum copper Alloys near guinier preston zones
    Journal of Applied Physics, 2016
    Co-Authors: I A Bryukhanov, A V Larin

    Abstract:

    This article is devoted to a molecular dynamics simulation study of partial dislocation loop nucleation with respect to its mechanism and rate, and its propagation process under high shear stress in Aluminum-Copper Alloys. The mechanisms of dislocation nucleation near Guinier-Preston (GP) zones of various diameters and concentrations have been analyzed. Dislocation nucleation rates near plain GP Cu-zones with diameters of 3.5, 7.5, and 13.5 nm and at various concentrations have been calculated using the mean lifetime method with temperatures in range of 100 and 700 K. It has been found that depending on the temperature and applied stress, the dislocation can nucleate either from the edge, or from the plain area of a GP zone. The dislocation nucleation is preceded by a generation of defect clusters that are formed due to local opposite atomic shifts in two adjacent (111) planes by the half-length of a Burgers vector of a partial dislocation. The expansion of a partial dislocation loop can be accompanied by…

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Hai-lung Tsai – One of the best experts on this subject based on the ideXlab platform.

  • Modeling of solute redistribution in the mushy zone during solidification of Aluminum-Copper Alloys
    Metallurgical Transactions A, 1993
    Co-Authors: Q. Z. Diao, Hai-lung Tsai

    Abstract:

    A mathematical model has been established to predict the formation of macrosegregation for a unidirectional solidification of Aluminum-Copper Alloys cooled from the bottom. The model, based on the continuum formulation, allows the calculation of transient distributions of temperature, velocity, and species in the solidifying alloy caused by thermosolutal convection and shrinkage-induced fluid flow. Positive segregation in the casting near the bottom (inverse segregation) is found, which is accompanied by a moving negative-segregated mushy zone. The effects of shrinkage-induced fluid flow and solute diffusion on the formation of macrosegregation are examined. It is found that the redistribution of solute in the solidifying alloy is caused by the flow of solute-rich liquid in the mushy zone due to solidification shrinkage. A higher heat-extraction rate at the bottom increases the solidification rate, decreasing the size of the mushy zone, reducing the flow of solute-rich liquid in the mushy zone and, as a result, lessening the severity of inverse segregation. Comparisons between the theoretical predictions from the present study and previous modeling results and available experimental data are made, and good agreements are obtained.

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  • The formation of negative- and positive-segregated bands during solidification of Aluminum-Copper Alloys
    International Journal of Heat and Mass Transfer, 1993
    Co-Authors: Q. Z. Diao, Hai-lung Tsai

    Abstract:

    Abstract The evolution of macrosegregation, appearing in the form of negative- and positive-segregated bands, in an Aluminum-Copper alloy unidirectionally solidified from the bottom has been analyzed numerically. It is found that a negative-segregated band is formed in the solidified casting if the casting is quenched during solidification. On the other hand, a positive-segregated band is created resulting from a sudden decrease of heat extraction rate at the bottom of the casting. Multiple negative- and positive-segregated bands could be formed in the solidified casting if the thermal boundary condition at the bottom of the casting fluctuates with time. The predicted banding segregation in the solidified alloy compares favorably with the available experimental data.

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  • Inverse segregation for a unidirectional solidification of Aluminum-Copper Alloys
    International Journal of Heat and Mass Transfer, 1993
    Co-Authors: J. H. Chen, Hai-lung Tsai

    Abstract:

    Abstract A mathematical model has been developed to simulate the inverse segregation for a unidirectional solidification of Al-Cu Alloys cooled from the bottom. It is found from the present study that the fluid flow of solute-rich liquid in the mushy zone caused by solidification shrinkage is the main driving force for the formation of inverse segregation. The predicted copper concentration in the solidified Alloys is in good agreement with the published experimental data. Several interesting transient behaviors of solute redistribution in the mushy zone, which were not reported before, are also discussed.

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