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Microstructures and phase transformations in interstitial alloys of tantalum

Technical Report ·
DOI:https://doi.org/10.2172/6170360· OSTI ID:6170360

The analysis of microstructures, phases, and possible ordering of interstitial solute atoms is fundamental to an understanding of the properties of metal-interstitial alloys in general. As evidenced by the controversies on phase transformations in the particular system tantalum--carbon, our understanding of this class of alloys is inferior to our knowledge of substitutional metal alloys. An experimental clarification of these controversies in tantalum was made. Using advanced techniques of electron microscopy and ultrahigh vacuum techology, an understanding of the microstructures and phase transformations in dilute interstitial tantalum--carbon alloys is developed. Through a number of control experiments, the role and sources of interstitial contamination in the alloy preparation (and under operating conditions) are revealed. It is demonstrated that all previously published work on the dilute interstitially ordered phase Ta/sub 64/C can be explained consistently in terms of ordering of the interstitial contaminants oxygen and hydrogen, leading to the formation of the phases Ta/sub 12/O and Ta/sub 2/H.

Research Organization:
California Univ., Berkeley (USA). Lawrence Berkeley Lab.
DOE Contract Number:
W-7405-ENG-48
OSTI ID:
6170360
Report Number(s):
LBL-8661
Country of Publication:
United States
Language:
English