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Final Thesis_Claudine_8-18-2017.pdf (4.93 MB)

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Influence Of Cross-Section Change During Directional Solidification On Dendrite Morphology, Macrosegregation And Defect Formation In Pb-6 wt Sb Alloy

Lacdao, Claudine
http://rave.ohiolink.edu/etdc/view?acc_num=csu1503321612987996

Abstract Details

2017, Master of Science in Chemical Engineering, Cleveland State University, Washkewicz College of Engineering.
The purpose of this research is to examine the dendrite array morphology, macrosegregation, and defect formation caused by the fluid flow at the abrupt cross-section changes during directional solidification of Pb-6% Sb alloy. Four 24-cm long cylindrical alloy samples were directionally solidified in graphite crucibles: two having a constant diameter (9-mm) grown at 10.4 and 63.1 μm s-1 , one having an abrupt cross-section decrease (from 12.7 to 6.35 mm) and one having an abrupt increase (from 6.35 to 12.7 mm) by pulling down the alloy containing cylindrical graphite crucibles from the upper hot-zone of a stationary vertical furnace into its cold-zone below. Microstructures were examined on transverse slices cut along the length of the directionally solidified samples. Dendrite spacing and distribution were characterized on these transverse sections. The Pb-6% Sb alloy was selected as a low melting point analog for commercially used multicomponent nickel-base superalloys, because its thermophysical properties are well characterized. Also, a density inversion occurs in the inter-dendritic melt in the “mushy-zone” during directional solidification of this alloy, because the density of the melt decreases as Sb content increases from the array tips at the top of the mushy zone to the eutectic at their bottom. In constant cross-section crucibles, the formation of dendrite-trees in the mushy zone will be subject only to this “plume type” convection as solidification proceeds from the bottom end of the crucible to its top. Whereas in crucibles with abrupt cross-section change, the solidifying mushy-zone will be subject to additional “cross-section change induced” solidification shrinkage flow, when the speed of the liquid flowing downwards to feed the solidification shrinkage occurring below, will either suddenly accelerate or decelerate, because of the abrupt area change. This sudden change in the incoming fluid speed may break slender side-branches of dendrite trees. These broken dendrite fragments may rotate, sink, and grow further to develop into misaligned “spurious” grains. The “plume type of flow” is different than the “steepling convection flow” which was recently examined during directional solidification of Al-19% Cu and Al-7% Si alloys by Dr. Masoud Ghods in our laboratory.
Surendra Tewari, Ph.D. (Committee Chair)
Orhan Talu, Ph.D. (Committee Member)
Christopher Wirth, Ph.D. (Committee Member)
Nolan Holland, Ph.D. (Committee Member)
86 p.
Chemical Engineering
Cross-Section Change; Directional Solidification; Dendrite Morphology; Macrosegregation And Defect Formation In Pb-6 wt Sb Alloy; Density Inversion; Dendrite Trunk Diameter; Nearest Neighbor Spacings; Lead Antimony Alloy; Binary Alloy

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Citations

  • Lacdao, C. (2017). Influence Of Cross-Section Change During Directional Solidification On Dendrite Morphology, Macrosegregation And Defect Formation In Pb-6 wt Sb Alloy [Master's thesis, Cleveland State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=csu1503321612987996

    APA Style (7th edition)

  • Lacdao, Claudine. Influence Of Cross-Section Change During Directional Solidification On Dendrite Morphology, Macrosegregation And Defect Formation In Pb-6 wt Sb Alloy . 2017. Cleveland State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=csu1503321612987996.

    MLA Style (8th edition)

  • Lacdao, Claudine. "Influence Of Cross-Section Change During Directional Solidification On Dendrite Morphology, Macrosegregation And Defect Formation In Pb-6 wt Sb Alloy ." Master's thesis, Cleveland State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=csu1503321612987996

    Chicago Manual of Style (17th edition)

csu1503321612987996
424
© 2017, some rights reserved.Creative Commons License Influence Of Cross-Section Change During Directional Solidification On Dendrite Morphology, Macrosegregation And Defect Formation In Pb-6 wt Sb Alloy by Claudine Lacdao is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by Cleveland State University and OhioLINK.