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Monday, July 27, 2020 | History

3 edition of Macrosegregation in directionally solidified Pb-Sn alloys found in the catalog.

Macrosegregation in directionally solidified Pb-Sn alloys

Macrosegregation in directionally solidified Pb-Sn alloys

project closing report

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  • 40 Currently reading

Published by National Aeronautics and Space Administration, National Technical Information Service, distributor in [Washington, DC, Springfield, Va .
Written in English

    Subjects:
  • Solidification.,
  • Tin alloys.,
  • Lead alloys.,
  • Chemical fractionation.

  • Edition Notes

    StatementPI, Surendra N. Tewari.
    SeriesNASA contractor report -- NASA CR-208245
    ContributionsUnited States. National Aeronautics and Space Administration.
    The Physical Object
    FormatMicroform
    Pagination1 v.
    ID Numbers
    Open LibraryOL17133157M

    In our work, we have used a finite element algorithm to calculate macrosegregation and the formation of channels and freckles in Pb-Sn alloys. The algorithm has also been used to reproduce a calculation for horizontal solidification of an NH4C1-H2O solution presented in Ref. [3]. Calculations presented herein show that the present model is capable. produces macrosegregation along the sample length;[1,2] when severe, it also produces channel segregates (or freckles).[3–13] Based on the measurements of dendrite specific surface area (S v) in the quenched mushy zone of directionally solidified Pb-Sb and Pb-Sn alloys, we recently reported[14] that S v 1 1 S* ( ), where.

    The alloys Pb wt pct Sb and Pb wt pct Sb were directionally solidified with three different thermal gradients of 40, 86, and K cm 21 at growth rates ranging from to 30 mms A Gaussian peak amplitude analysis of the cell/dendrite spacing distribution shows a distinct peak. An investigation into the influence of a transverse magnetic field ( T) on the mushy zone morphology and macrosegregation in directionally solidified hypoeutectic Pb-Sn alloy shows that the.

    Bi–Ag alloys have been stressed as possible alternatives to replace Pb-based solder alloys. Although acceptable melting temperatures and suitable mechanical properties may characterize such alloys, as referenced in literature, there is a lack of comprehension regarding their microstructures (morphologies and sizes of the phases) considering a composition range from to wt.%Ag. Tewari SN, Shah R, Song H. Effect of magnetic field on the microstructure and macrosegregation in directionally solidified Pb-Sn alloys. Metall. Mater. Trans. A. ; 25A– doi: /BF [Google Scholar].


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Macrosegregation in directionally solidified Pb-Sn alloys Download PDF EPUB FB2

Macrosegregation is present in the weld fusion zone in the case of laser welding of dissimilar materials 20 or using a filler wire different in chemical composition from the base metal.

23 Mixing or steering of melt in the molten pool can reduce macrosegregation. The cross section and schematic of a laser weld, EDX analysis results of Fe and Ni elements and line analysis results of Fe and Ni. In this article, gravity-driven flow and its subsequent effect of promoting macrosegregation during unidirectional solidification of dendritic Macrosegregation in directionally solidified Pb-Sn alloys book is presented.

Examples of macrosegregation that arise during the controlled directional solidification of hypo- and hypereutectic Pb−Sn alloys are shown, and a method of preventing macrosegregation is by:   Tewari and Shah reported macrosegregation along the lengths of 11 small-diameter (7 mm) rods of Pb–Sn alloys (10–58 wt.% Sn) that were directionally solidified in positive thermal gradients (melt on top, solid below, and gravity pointing downward).

The results presented here are numerical simulations of the 11 cases using the compositions (C 0), thermal gradients (G), withdrawal Cited by: An investigation into the influence of a transverse magnetic field ( T) on the mushy zone morphology and macrosegregation in directionally solidified hypoeutectic Pb-Sn alloy shows that the field has no influence on the morphology of dendritic.

Cruz et al. investigated the wear performance of Al and 20 wt.%Sn alloys samples directionally solidified under solidification cooling rates in the range 1−20 K/s, and reported microstructures, for any examined sample, formed by an Al-rich dendritic matrix with the Sn-rich eutectic mixture distributed along the interdendritic regions.

The Author: Ricardo Oliveira, Thiago A. Costa, Marcelino Dias, Camila Konno, Noé Cheung, Amauri Garcia. An investigation into the influence of a transverse magnetic field ( T) on the mushy zone morphology and macrosegregation in directionally solidified hypoeutectic Pb-Sn alloy shows that the field has no influence on the morphology of dendritic arrays.

The field does, however, cause severe distortion in the cellular array morphology. The numerical simulation of macrosegregation formation during the horizontal solidification of a Sn-3 wt%Pb alloy in a rectangular cavity is presented and compared to experimental results.

The benchmark experiment consists in solidifying a rectangular ingot of Sn-3 wt%Pb alloy using a solidification setup with a precise control of the thermal. Effects of traveling magnetic field (TMF) on freckle formation of directionally solidified Pb–Sn alloys were investigated experimentally and numerically.

The experimental results demonstrated that freckles could form without any magnetic field and with the upward TMF. In. Macrosegregation has been observed in directionally solidified Pb pct Sn alloys, over a range of freezing rates and temperature gradients.

The macrosegregation was shown to result from the upward flow of less dense, tin rich, interdendritic liquid during solidification, using radioactive tracer techniques.

For comparison, it was shown that macrosegregation occurred in the opposite direction. Applying RMF in a directionally solidified AlSi7Mg alloy, Zimmermann et al. found that the forced flow resulted in axial macro segregation (rich silicon) in the centre part of sample.

Meanwhile, Zaïdat et al. reported that a freckled segregation in the directionally solidifying Al– wt%Ni alloy was induced under the influence of TMF [34]. Macrosegregation along the length of the directionally solidified samples is produced when Pb-Sn alloys (10 to 58 wt pct Sn) are directionally solidified in a positive thermal gradient (melt on top, solid below, and gravity pointing down) with.

Thermosolutal convection in the dendritic mushy zone occurs during directional solidification of hypoeutectic lead tin alloys in a positive thermal gradient, with the melt on the top and the solid below.

This results in macrosegregation along the length of the solidified samples. been examining macrosegregation in hypoeutectic Pb-Sn alloys, directionally solidified in a positive thermal gradi- ent, the melt on the top and the solid below. Under such growth conditions, the temperature profile alone is expected to be stabilizing against natural convection.

However, the. In this article, gravity-driven flow and its subsequent effect of promoting macrosegregation during unidirectional solidification of dendritic alloys is presented.

Examples of macrosegregation that arise during the controlled directional solidification of hypo- and hypereutectic Pb-Sn alloys are shown, and a method of preventing macrosegregation is demonstrated.

Macrosegregation along the length of the directionally solidified samples is produced when Pb-Sn alloys (10 to 58 wt pct Sn) are directionally solidified in a positive thermal gradient (melt on top, solid below, and gravity pointing down) with steady-state dendritic arrayed morphology (the length of the mushy zone, much smaller than the initial length of the melt column, remaining nearly.

Macrosegregation in Directionally Solidified Pb-Sn Alloys S.N. TEWARI, RAJESH SHAH, and HUI SONG An investigation into the influence of a transverse magnetic field ( T) on the mushy zone morphology and macrosegregation in directionally solidified hypoeutectic Pb-Sn alloy shows.

been examining macrosegregation in hypoeutectic Pb-Sn alloys, directionally solidified in a positive thermal gradi-ent, the melt on the top and the solid below. Under such growth conditions, the temperature profile alone is expected to be stabilizing against natural convection.

However, the interdendritic solutal profile is destabilizing. Get this from a library. Macrosegregation in directionally solidified Pb-Sn alloys: project closing report. [Surendra N Tewari; United States. National Aeronautics and Space Administration.]. been examining macrosegregation in hypoeutectic Pb-Sn alloys, directionally solidified in a positive thermal gradi- ent, the melt on the top and the solid below.

MACROSEGREGATION OF DIRECTIONALLY SOLIDIFIED LEAD - TIN ALLOYS K V Sreenivas Rao1 *Corresponding Author: K V Sreenivas Rao, [email protected] Directional solidification experiments were carried out on hypoeutectic and hypereutectic Pb-Sn alloys.

Different combinations of growth rate V and composition Co. were used to investigate. Effect of a transverse magnetic field on macrosegregation and growth of primary Al 2 Cu dendrites in directionally solidified Al–40 wt% Cu alloys was investigated experimentally.

The experimental results indicated that the magnetic field caused the formation of channel-like and freckle segregations.MACROSEGREGATION IN DIRECTIONALLY SOLIDIFIED Pb_Sn Alloys ABSTRACT-Thermosolutal convection in the dendritic mushy zone occurs dudng directional soli,dification of hypoeutectic lead tin alloys in a positive thermal gradient, with the melt on the top and the solid below.

This results in macrosegregation along the length of the solidified samples.CiteSeerX - Document Details (Isaac Councill, Lee Giles, Pradeep Teregowda): Directional solidification experiments were carried out on hypoeutectic and hypereutectic Pb-Sn alloys.

Different combinations of growth rate V and composition Co. were used to investigate their effect on longitudinal macro segregation.

Macro segregation along the length of the samples was observed in hypoeutectic Pb.