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The Effects of Cooling Rate Upon Xdt m TiAl Weld Microstructure

Published online by Cambridge University Press:  21 February 2011

Erica Robertson
Affiliation:
Air Force Office of Scientific Research, Bolling AFB, Washington, D.C. 20332
Mary Ann Hill
Affiliation:
Materials Science and Technology Division and Center for Materials Science Los Alamos National Laboratory. Los Alamos, NM 87545
Ricardo B. Schwarz
Affiliation:
Materials Science and Technology Division and Center for Materials Science Los Alamos National Laboratory. Los Alamos, NM 87545
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Abstract

Fusion zone microstructures of an electron beam (EB) welded XDt m Ti–48at%Al + 6.5 vol% TiB2 alloy revealed plate-like precipitates which were absent in the base metal. The volume fraction of this phase increased with increasing cooling rate and correlated with increased weld cracking frequency. To determine whether this phase was a product of solidification from the melt or a product of a solid-state transformation, the microstructures of the welds were compared to those of samples cycled in a Gleeble 1500/20 Thermal-Mechanical Test System which was programmed to simulate the solid-state portion of the weld cooling rates (as predicted by a Rosenthal analysis). The microstructures were characterized by X-ray diffraction, optical and by scanning electron microscopy. The plate-like phase found in the weld microstructures was identified as TiB2 occurring upon rapid solidification of the melted weld metal.

Type
Research Article
Copyright
Copyright © Materials Research Society 1990

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