Stress corrosion cracking of uranium alloys
Literature data show that two types of stress-corrosion cracking occur in uranium alloys; transgranular and intergranular. Two completely different types of mechanisms have been proposed for these modes. The transgranular cracking is attributed to a mechanical mechanism dealing with stresses generated by the reaction product while the intergranular cracking is attributed to either H/sub 2/ embrittlement or an anodic dissolution process. The data show that the intergranular cracking occurs more rapidly, and when conditions are such that both types of cracking can occur, the intergranular mode usually predominates. Since intergranular cracking initiates more easily than the transgranular type it has been the most common type. Conditions which favor intergranular cracking include high alloy addition levels, environments containing H/sub 2/O or Cl-ions. High temperature aging has been found to eliminate stress corrosion cracking in some alloys, or at least reduce the susceptibility. This behavior is most likely due to the elimination of the intergranular cracking path (prior gamma grain boundaries). Transgranular stress corrosion cracking has been observed in U alloys when precracked specimens are used. In uranium alloys with low alloy additions this mode is observed in all environments tested, but in the alloys with higher addition levels the mode is observed only in air tests. While the details of the cracking mechanism may not be well understood, enough is now known about uranium alloy stress corrosion cracking to permit the safe use of the alloys under the proper conditions. A few points should be kept in mind: (1) As the strength of an alloy increases the susceptibility to stress-corrosion cracking increases. This has been observed in the U--Nb and U-Ti systems. (2) As the corrosion resistance increases the susceptibility to cracking increases. This seems to hold true of all of the uranium alloys. (3) Care should be taken in the application of uranium alloy stress corrosion data because of difference in behavior observed between smooth and precracked specimens. (auth)
- Research Organization:
- Sandia Labs., Albuquerque, N.Mex. (USA)
- NSA Number:
- NSA-29-024649
- OSTI ID:
- 4335151
- Report Number(s):
- SLA--74-5037; CONF-740205--1
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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