Grain-shape parameters for high-temperature creep resistance in powder metallurgy tungsten fine wires
- Kyushu Inst. of Tech., Kitakyushu (Japan). Dept. of Materials Science and Engineering
Three grain-shape parameters, f{sub 1}, f{sub 2}, and f{sub 3}, are defined to clarify the morphological effect of grains on the high-temperature creep resistance under the condition that no grain boundary cavitation occurs. The parameter f{sub 1} is characteristic of complicated grain shapes, suggesting that it can be a measure of the interlocking grain structure. The parameter f{sub 2} is an important parameter when torsional stresses are imposed on coiled wires, and f{sub 3} is characteristic of the short-range roughness of grain boundaries only when f{sub 1} is not greatly changed. The minimum creep rate decreases as the grain aspect ratio, R, increases for R < 30, and the creep rate increases as R increases for R > 30. The parameter f{sub 1}, as well as Raj and Ashby`s model, gives a satisfactory explanation for the former behavior. On the other hand, it is proven that their model must be modified using f{sub 3} to explain the latter behavior because of the highly elongated grain configuration that is associated with R > 30.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 611584
- Journal Information:
- Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science, Vol. 29, Issue 2; Other Information: PBD: Feb 1998
- Country of Publication:
- United States
- Language:
- English
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