Freeze-dried processing of tungsten heavy alloys
Tungsten heavy alloy powders were produced from freeze-dried aqueous solutions of ammonium metatungstate and, principally, sulfates of Ni and Fe. The freeze-dried salts were calcined and hydrogen reduced to form very fine, homogeneous, low-density, W heavy alloy powders having a coral-like structure with elements of approximately 0.1 /mu/m in diameter. The powders yield high green strength and sinterability. Tungsten heavy alloy powders of 70%, 90%, and 96% W were prepared by freeze drying, compacted, and solid-state (SS) sintered to fully density at temperatures as low as 1200/degree/C and also at conventional liquid-phase (LP) sintering temperatures. Solid-state sintered microstructures contained polygonal W grains with high contiguity; the matrix did not coat and separate the W grains to form low-contiguity, high-ductility structures. Liquid-phase sintered microstructures were very conventional in appearance, having W spheroids of low contiguity. All these materials were found to be brittle. High levels of residual S accompanied by segregation of the S to all the microstructural interfaces are principally responsible for the brittleness; problems with S could be eliminated by using Fe and Ni nitrates rather than the sulfates. 9 refs., 22 figs., 3 tabs.
- Research Organization:
- Pacific Northwest Lab., Richland, WA (USA)
- DOE Contract Number:
- AC06-76RL01830
- OSTI ID:
- 5980934
- Report Number(s):
- PNL-6887; ON: DE89015171
- Country of Publication:
- United States
- Language:
- English
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Processing and alloying of tungsten heavy alloys
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Related Subjects
360101* -- Metals & Alloys-- Preparation & Fabrication
360102 -- Metals & Alloys-- Structure & Phase Studies
360103 -- Metals & Alloys-- Mechanical Properties
ALLOYS
CALCINATION
CHEMICAL ANALYSIS
CHEMICAL PREPARATION
CHEMICAL REACTIONS
CRYSTAL STRUCTURE
DECOMPOSITION
DRYING
FABRICATION
GRAIN SIZE
HARDNESS
MECHANICAL PROPERTIES
MICROSTRUCTURE
PARTICLE SIZE
POWDERS
PYROLYSIS
RECOMMENDATIONS
SINTERING
SIZE
SYNTHESIS
THERMOCHEMICAL PROCESSES
TUNGSTEN ALLOYS
TUNGSTEN BASE ALLOYS