Characteristics of commercial vacuum-hot-pressed beryllium. Part II. Summary report
BS>Tensile property evaluations of hot-pressed beryllium blocks revealed the presence of embrittlement in the pressing direction at 500 deg F at a strain rate of 0.0385 per minute. The embrittlement was found to be exaggerated at a strain rate of 38.5 per minute, also occurring at 300 deg F. It was traced to the excessively high yield strength of this material and was felt to originate from a combination of fine grain size and impurity locking. The comparatively low ultimate strength in the pressing direction, a result of preferred crystallographic orientation, was another key factor leading to the embrittlement in the pressing direction. The effect of strain rate on the tensile properties of hot-pressed blocks 21 and 24 was investigated further. Mild manifestations of embrittlement were revealed in these materials at a strain rate of 38.5 per minute. Negative or very low strain-rate sensitivities in yield and ultimate tensile strengths found in hot-pressed block 21 at intermediate strain rates and at temperatures between amibient and 500 deg F were interpreted as evidence of strain-aging behavior. A transmission-electron-microscopy investigation of hot- pressed block 20 revealed the general presence of long straight dislocations after pressurization to 20.3 kbar. This observation was used to explain qualitatively the removal of the yield point by pressurization. (auth)
- Research Organization:
- Battelle Columbus Labs., Ohio (USA)
- NSA Number:
- NSA-29-016239
- OSTI ID:
- 4339209
- Report Number(s):
- BMI-X--639; UCRL--13589
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
DISLOCATIONS
ELECTRON MICROSCOPY
GRAIN ORIENTATION
GRAIN SIZE
HIGH TEMPERATURE
HOT PRESSING
IMPURITIES
LOW PRESSURE
N50230* --Metals
Ceramics
& Other Materials--Metals & Alloys--Properties
Structure & Phase Studies
STRAINS
TENSILE PROPERTIES
TIME DEPENDENCE
YIELD STRENGTH