STRESS CORROSION CRACKING IN URANIUM-MOLYBDENUM ALLOYS
An investigation was conducted to determine the cause of cracking, during tension, on the surface of tensile specimens of U--Mo alloys. The cracking was observed in alloys that were water quenched from a temperature range in which the body-centered cubic gamma phase was stable and, subsequently, stressed in tension. The investigation was carried out on alloys of U--Mo containing 5 and 4 wt% Mo. It was discovered early in the study that the cracking could be eliminated by testing tensile specimens in a He atmosphere. Because of this result, tensile tests were performed in vacuum O/sub 2/2, impure N/sub 2/, and purified N/sub 2/. Additional experiments were done to establish the relation of stress state, temperature, strain rate, O/sub 2/ pressure, stress magnitude, and grain size to the cracking phenomenon. U--4 wt% Mo and U--5 wt% Mo were compared with respect to microstructure and crystal structure, since both alloys cracked during the tensile test. The origin and propagation of cracks in the microstructure were studied, using motion pictures and metallography. The results of the various experiments showed that the cracking occurred only in tension and was caused by stress-corrosion cracking due to the presence of O/sub 2/ in the atmosphere. The rate of cracking increased as the temperature was increased above 25 deg C. Below 10 deg C cracking was not observed in the U-5 wt% Mo alloy. Cracking was not associated with just one metastable phase. since it was observed in both the U-5 wt% Mo and U-4 wt% Mo alloys, which have different crystal structures when rendered metastable by water quenching from the gamma phase field. The path of fracture was transgranular and was not associated with deformation markings in the grains. (auth)
- Research Organization:
- Union Carbide Nuclear Co. Y-12 Plant, Oak Ridge, Tenn.
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- W-7405-ENG-26
- NSA Number:
- NSA-17-032518
- OSTI ID:
- 4679428
- Report Number(s):
- Y-1417
- Resource Relation:
- Other Information: Orig. Receipt Date: 31-DEC-63
- Country of Publication:
- United States
- Language:
- English
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