TRANSFORMATION CHARACTERISTICS OF ZIBCONIUM-NIOBIUM ALLOYS. Interim Technical Report No. 3
Technical Report
·
OSTI ID:4123993
High-temperature aging reactions in hypermonotectoid Nb-- Zr alloys were found to be relatively complex and involve at least two and possibly three mechanisms. A cellular mode of decomposition was observed at temperatures both above and below the monotectoid temperature (610 deg C). This mode of decomposition appeared to reflect pnimarily the tendency of the system to segregate into niobium-rich and niobium-poor regions rather than a eutectoidal type of decomposition of beta simultaneously supersaturated with respect to both alpha and beta /sub Nb/. Evidence for this is provided by the fact that direct precipitation of alpha from beta competed with the cellular reaction at sufficiently low temperatures. Single crystal studies of the omicron reaction confirmed conclusions that omicron present in quenched 12% niobium alloys is supersaturated in niobium. The temperature at which this omicron forms on quenching appeared to be near 300 deg C. The queuched omicron is a highly imperfect structure and consists of thin platelets parallel to beta (110) planes. Quenched omicron can be interpreted as a highly faulted structure and preliminary results suggest that the degree of faulting increases with niobium content of the alloy. Changes that occur on aging of quenched omicron reflect annealing out of stacking faults and adjustments of composition to the values demanded by metastable equilibrium of omicron with beta . Tempering of martensite in the 5% niobium alloy appeared to be a relatively simple process involving the precipitation of a niobium-rich beta phase from supersatuxated alpha . Substantial hardening accompanied this precipitation process. (auth)
- Research Organization:
- Case Inst. of Tech., Cleveland
- NSA Number:
- NSA-15-000633
- OSTI ID:
- 4123993
- Report Number(s):
- TID-6445
- Country of Publication:
- United States
- Language:
- English
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