TENSILE FAILURE OF QMV BERYLLIUM FROM ROOM TEMPERATURE TO 870 C
Short-time tensile tests of hot-pressed QMV beryllium were made at temperatures of 20 to 870 deg C. Mechanical properties were correlated with BeO content (0.8 to 2.0%) and with microstructure. Elongation increased with temperature to a maximum at 425 deg C, decreased to 760 deg C, and again increased at 815 deg C for samples with low BeO content. Samples with 2% BeO exhibited no increase in elongation at 815 deg C. Fracture was transcrystalline to 480 deg C, initiated by stress concentration at twin intersections, intersections of twins with grain boundaries, at {1012} twin-matrix interfaces, and at impurity particles, particularly carbides. Intercrystalline fractures, starting at 480 deg C, were characterized by void formation at grain boundaries normal to the stress axis. The amount of cavitation increased to a maximum at 760 deg C, and thereafter decreased as the temperature increased to 870 deg C. Voids were observed to have nucleated at carbide particles in grain boundaries. Presumably other impurities, such as BeO, are also capable of nucleating voids, although no direct confirmation of this could be obtained because such particles were small in comparison to the size of the voids. Striking evidence for the role of impurities in void formation was obtained in alloys of low BeO content, which contained several clusters of very large grains in a fine-grained matrix. The boundaries of these large grains were free of visible impurity particles and contained no intercrystalline voids, while the surrounding fine-grained materials contained impurity particles in the grain boundaries and numerous voids and cracks. Current fracture theories are used to explain the role of impurities and mechanical effects, e.g., grain boundary sliding and migration, as factors which contribute to intercrystalline failure of beryllium at elevated temperature. (auth)
- Research Organization:
- Lockheed Aircraft Corp. Missiles and Space Div., Sunnyvale, Calif.
- NSA Number:
- NSA-15-017300
- OSTI ID:
- 4017692
- Report Number(s):
- LMSD-89083
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
Similar Records
TENSILE PROPERTIES OF BRUSH BERYLLIUM QMV MATERIAL AT ROOM AND ELEVATED TEMPERATURES
THE TENSILE, NOTCHED TENSILE AND TENSILE IMPACT PROPERTIES OF CROSS-ROLLED - 100 MESH QMV BERYLLIUM SHEET. Progress Report No. 1
Related Subjects
BERYLLIUM
BERYLLIUM OXIDES
BUBBLES
CARBIDES
CRACKS
CRYSTALS
FAILURES
FINS
GRAIN BOUNDARIES
HIGH TEMPERATURE
IMPURITIES
MECHANICAL PROPERTIES
METALLOGRAPHY
METALS, CERAMICS, AND OTHER MATERIALS
NUCLEATE BOILING
PARTICLES
PRESSURE
QUANTITY RATIO
SAMPLING
SURFACES
TEMPERATURE
TENSILE PROPERTIES
TESTING
ZONES