ANNEALING WARM-EXTRUDED ZIRCALOY-2 TO AN ULTRAFINE GRAIN SIZE
Zircaloy-2 was warm extruded twice with an intermediate vacuum anneal. It was then heat treated in a salt bath for various time spans at temperatures of 1100, 1200, and 1300 deg F. Recrystallization and softening of this heavily worked metal were complete after 16 minutes at 1100 deg F, 4 minutes at 1200 deg F, and 1 minute at 1300 deg F. Ultrafine grains with an average diameter of about six microns were produced by annealing in the salt bath for 16 minutes at 1100 deg F; larger grains were produced with the longer times and higher temperatures. Vacuum annealing produced slightly larger grains than salt annealing, probably because of a slower heating rate. The extensive cold working of the metal is apparently the major factor in producing the fine grains. It was concluded that an average grain diameter of six microns or smaller can be produced with the following conditions: a highly cold-worked structure, such as that provided by warm extruding twice (10: 1 extrusion ratio) with an intermediate low temperature anneal; a short annealing time at a low-annealing temperature, such as 16 minutes at 1100 deg F; and a rapid heating to the annealing temperature, similar to that afforded by the salt bath. Other work on salt bath annealing at Ha ford showed no significant hydrogen contamination of the Zircaloy, nor was the corrosion resistance of the metal to water or steam affected by salt bath annealing for the cycles recommended above. (auth)
- Research Organization:
- General Electric Co. Hanford Atomic Products Operation, Richland, Wash.
- DOE Contract Number:
- AT(45-1)-1350
- NSA Number:
- NSA-15-031143
- OSTI ID:
- 4840122
- Report Number(s):
- HW-68835
- Country of Publication:
- United States
- Language:
- English
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