A comparison of the microstructures of As-cast and laser surface melted Ti-8Al-4Y

D. G. Konitzer, B. C. Muddle, H. L. Fraser

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Abstract

A Ti-8 at. pct Al-4 at. pct Y alloy has been cast in small quantities and subjected to laser surface melting treatments in an effort to produce a uniform distribution of fine-scale dispersoids by internal oxidation. The microstructures of both as-cast and laser-modified material have been characterized using transmission electron microscopy, energy dispersive X-ray spectroscopy, and convergent beam electron diffraction, and the identity and distribution of second phase dispersoids established. An ability to refine significantly the dendritic structure of the as-cast alloy by laser surface treatment is demonstrated. The matrix phase of the modified alloy is martensitic α′, in contrast to the α phase of the as-cast material. The interdendritic phase observed in both as-cast and laser-modified material and the fine-scale dispersed particles (50 to 70 nm) in the as-cast alloy are shown to be rich in Y, with a structure consistent with that of the oxide Y2O3. Dispersoids within the laser modified zone are typically 8 to 20 nm in diameter and show a tendency to form preferentially at interlath boundaries of the martensite. The origins of these structures and their potential effects on the mechanical properties of the alloy are discussed briefly.

Original languageEnglish
Pages (from-to)1979-1988
Number of pages10
JournalMetallurgical Transactions A - Physical Metallurgy and Materials Science
Volume14
Issue number10
DOIs
Publication statusPublished - 1 Oct 1983
Externally publishedYes

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