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Effect of Convection Associated with Cross-section Change during Directional Solidification of Binary Alloys on Dendritic Array Morphology and Macrosegregation.

Record Type:	Language materials, manuscript : Monograph/item
Title/Author:	Effect of Convection Associated with Cross-section Change during Directional Solidification of Binary Alloys on Dendritic Array Morphology and Macrosegregation./
Author:	Ghods, Masoud.
Description:	1 online resource (117 pages)
Notes:	Source: Dissertation Abstracts International, Volume: 79-01(E), Section: B.
Subject:	Chemical engineering. -
Online resource:	click for full text (PQDT)
ISBN:	9780355186536

Effect of Convection Associated with Cross-section Change during Directional Solidification of Binary Alloys on Dendritic Array Morphology and Macrosegregation.
Ghods, Masoud.

Effect of Convection Associated with Cross-section Change during Directional Solidification of Binary Alloys on Dendritic Array Morphology and Macrosegregation. - 1 online resource (117 pages)

Source: Dissertation Abstracts International, Volume: 79-01(E), Section: B.

Thesis (D.Engr.)--Cleveland State University, 2017.

Includes bibliographical references

This dissertation explores the role of different types of convection on macrosegregation and on dendritic array morphology of two aluminum alloys directionally solidified through cylindrical graphite molds having both cross-section decrease and increase. Al- 19 wt. % Cu and Al-7 wt. % Si alloys were directionally solidified at two growth speed of 10 and 29.1 mum s-1 and examined for longitudinal and radial macrosegregation, and for primary dendrite spacing and dendrite trunk diameter.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2018

Mode of access: World Wide Web

ISBN: 9780355186536Subjects--Topical Terms:

555952
Chemical engineering.
Index Terms--Genre/Form:

554714
Electronic books.

Effect of Convection Associated with Cross-section Change during Directional Solidification of Binary Alloys on Dendritic Array Morphology and Macrosegregation.
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245 1 0 $a Effect of Convection Associated with Cross-section Change during Directional Solidification of Binary Alloys on Dendritic Array Morphology and Macrosegregation.
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500 $a Source: Dissertation Abstracts International, Volume: 79-01(E), Section: B.
500 $a Adviser: Surendra Tewari.
502 $a Thesis (D.Engr.)--Cleveland State University, 2017.
504 $a Includes bibliographical references
520 $a This dissertation explores the role of different types of convection on macrosegregation and on dendritic array morphology of two aluminum alloys directionally solidified through cylindrical graphite molds having both cross-section decrease and increase. Al- 19 wt. % Cu and Al-7 wt. % Si alloys were directionally solidified at two growth speed of 10 and 29.1 mum s-1 and examined for longitudinal and radial macrosegregation, and for primary dendrite spacing and dendrite trunk diameter.
520 $a Directional solidification of these alloys through constant cross-section showed clustering of primary dendrites and parabolic-shaped radial macrosegregation profile, indicative of "steepling convection" in the mushy-zone. The degree of radial macrosegregation increased with decreased growth speed. The Al- 19 wt. % Cu samples, grown under similar conditions as Al-7 wt. % Si, showed more radial macrosegregation because of more intense "stepling convection" caused by their one order of magnitude larger coefficient of solutal expansion.
520 $a Positive macrosegregation right before, followed by negative macrosegregation right after an abrupt cross-section decrease (from 9.5 mm diameter to 3.2 mm diameter), were observed in both alloys; this is because of the combined effect of thermosolutal convection and area-change-driven shrinkage flow in the contraction region. The degree of macrosegregation was found to be higher in the Al- 19 wt. % Cu samples. Strong area-change-driven shrinkage flow changes the parabolic-shape radial macrosegregation in the larger diameter section before contraction to "S-shaped" profile. But in the smaller diameter section after the contraction very low degree of radial macrosegregation was found.
520 $a The samples solidified through an abrupt cross-section increase (from 3.2 mm diameter to 9.5 mm diameter) showed negative macrosegregation right after the cross-section increase on the expansion platform. During the transition to steady-state after the expansion, radial macrosegregation profile in locations close to the expansion was found to be "S-shaped". This is attributed to the redistribution of solute-rich liquid ahead of the mushy-zone as it transitions from the narrow portion below into the large diameter portion above.
520 $a Solutal remelting and fragmentation of dendrite branches, and floating of these fragmented pieces appear to be responsible for spurious grains formation in Al- 19 wt. % Cu samples after the cross-section expansion. New grain formation was not observed in Al-7 wt. % Si in similar locations; it is believed that this is due to the sinking of the fragmented dendrite branches in this alloy.
520 $a Experimentally observed radial and axial macrosegregations agree well with the results obtained from the numerical simulations carried out by Dr. Mark Lauer and Prof. David R. Poirier at the University of Arizona.
520 $a Trunk Diameter (TD) of dendritic array appears to respond more readily to the changing growth conditions as compared to the Nearest Neighbor Spacing (NNS) of primary dendrites.
533 $a Electronic reproduction. $b Ann Arbor, Mich. : $c ProQuest, $d 2018
538 $a Mode of access: World Wide Web
650 4 $a Chemical engineering. $3 555952
650 4 $a Physics. $3 564049
650 4 $a Condensed matter physics. $3 1148471
650 4 $a Materials science. $3 557839
650 4 $a High temperature physics. $3 1148654
650 4 $a Automotive engineering. $3 1104081
650 4 $a Engineering. $3 561152
650 4 $a Aerospace engineering. $3 686400
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710 2 $a ProQuest Information and Learning Co. $3 1178819
710 2 $a Cleveland State University. $b Washkewicz College of Engineering. $3 1148653
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=10645622 $z click for full text (PQDT)