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Secondary arm coarsening and microsegregation in superalloy PWA-1480 single crystals: Effect of low gravitySingle crystal specimens of nickel base superalloy PWA-1480 were directionally solidified on ground and during low gravity (20 sec) and high gravity (90 sec) parabolic maneuver of KC-135 aircraft. Thermal profiles were measured during solidification by two in-situ thermocouples positioned along the sample length. The samples were quenched during either high or low gravity cycles so as to freeze the structures of the mushy zone developing under different gravity levels. Microsegregation was measured by examining the solutal profiles on several transverse cross-sections across primary dendrites along their length in the quenched mushy zone. Effect of gravity level on secondary arm coarsening kinetics and microsegregation have been investigated. The results indicate that there is no appreciable difference in the microsegregation and coarsening kinetics behavior in the specimens grown under high or low gravity. This suggests that short duration changes in gravity/levels (0.02 to 1.7 g) do not influence convection in the interdendritic region. Examination of the role of natural convection, in the melt near the primary dendrite tips, on secondary arm spacings requires low gravity periods longer than presently available on KC-135. Secondary arm coarsening kinetics show a reasonable fit with the predictions from a simple analytical model proposed by Kirkwood for a binary alloy.
Document ID
19900010878
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Vijayakumar, M.
(Cleveland State Univ. OH., United States)
Tewari, S. N.
(Cleveland State Univ. OH., United States)
Lee, J. E.
(NASA Marshall Space Flight Center Huntsville, AL., United States)
Curreri, P. A.
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Date Acquired
September 6, 2013
Publication Date
January 1, 1990
Subject Category
Metallic Materials
Report/Patent Number
NAS 1.15:102445
NASA-TM-102445
E-5220
Meeting Information
Meeting: CSME Mechanical Engineering Forum 1990
Location: Toronto, Ontario
Country: Canada
Start Date: June 3, 1990
End Date: June 9, 1990
Sponsors: Canadian Society for Mechanical Engineering
Accession Number
90N20194
Funding Number(s)
CONTRACT_GRANT: NAG8-91
PROJECT: RTOP 647-27-05
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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