Effect of Grain Size on Creep Properties of a Tungsten
Author : Robert J. Buzzard
Publisher :
Page : 36 pages
File Size : 50,62 MB
Release : 1971
Category : Metals
ISBN :
Author : Robert J. Buzzard
Publisher :
Page : 36 pages
File Size : 50,62 MB
Release : 1971
Category : Metals
ISBN :
Author : Robert J. Buzzard
Publisher :
Page : 26 pages
File Size : 36,22 MB
Release : 1971
Category : Metals
ISBN :
Author : Robert J. Buzzard
Publisher :
Page : 26 pages
File Size : 22,92 MB
Release : 1971
Category :
ISBN :
Author : William D. Klopp
Publisher :
Page : 54 pages
File Size : 28,31 MB
Release : 1964
Category : Liquid metals
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Author : William D. Klopp
Publisher :
Page : 42 pages
File Size : 43,12 MB
Release : 1966
Category : Liquid metals
ISBN :
A study has been conducted of the properties of tungsten fabricated from three ingots consolidated by electron-beam melting. The study included purity as a function of number of melts, recrystallization a d grain growth behavior, low-temperature ductility, and high-temperature tensile and creep strength. The level of most metallic impurities in tungsten decreased with increasing number of electron-beam melts, the reduction being greatest for aluminum, iron, nickel, and silicon. The levels of interstitial impurities generally were not affected by remelting. Resistivity ratios for single crystals machined from ingot slices tended to increase on remelting. The recrystallization rates for worked, electron-beam- melted (EB-melted) tungsten were significantly higher than those observed earlier for arc-melted tungsten. The grain growth rates of EB-melted tungsten were higher than those reported previously for arc-melted tungsten, further reflecting the higher purity of the EB-melted materials. The activation energies for both recrystallization and grain growth in EB-melted tungsten were consistent with expected values assuming grain boundary self-diffusion to be the rate-controlling reaction. The ductile-brittle bend transition temperature for EB-melted tungsten is slightly higher in the worked condition than that reported for arc-melted tungsten. In the recrystallized conditions, the transition temperatures for EB- and arc-melted tungsten are similar. The tensile strength of EB-melted tungsten at 2500 to 4000 F is less than that of arc-melted tungsten. This is partly associated with the large grain size of EB-melted tungsten. However, when compared at the same grain size,
Author :
Publisher :
Page : 424 pages
File Size : 37,96 MB
Release : 1971
Category :
ISBN :
Author : Friedrich G. Ostermann
Publisher :
Page : 26 pages
File Size : 34,88 MB
Release : 1963
Category : Annealing of metals
ISBN :
Mechanical properties of powder-metallurgy tungsten were studied at low temperatures. Particular emphasis was placed on the effects of annealing temperatures and grain size on the ductile-brittle transition behavior. While room-temperature hardness and grain size were little sensitive to temperature changes within the 1500 to 2300 C range, tensile behavior was markedly influenced. Variation of grain size was achieved by straining and annealing. Grain size effects were evaluated in terms of the Petch-analysis. Fracture was at all times predominantly intergranular. The results of this investigation suggest that the high ductile-brittle transition temperature of tungsten is not sufficiently explained by strong dislocation-impurity atom interaction.
Author : William D. Klopp
Publisher :
Page : 28 pages
File Size : 30,80 MB
Release : 1971
Category : Hafnium compounds
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Author : Paul F. Sikora
Publisher :
Page : 20 pages
File Size : 37,34 MB
Release : 1959
Category : Aerospace engineering
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Author : Joseph R. Stephens
Publisher :
Page : 24 pages
File Size : 39,96 MB
Release : 1964
Category : Low temperatures
ISBN :
A study was undertaken to determine the effects of the interstitial impurities oxygen and carbon on the mechanical properties of polycrystalline tungsten and high-purity tungsten single crystals. Results of tensile tests showed that additions of both oxygen and carbon to polycrystalline tungsten produced a marked increase in the ductile to brittle transition temperature. Oxygen and carbon produced a much smaller increase in the transition temperature of the single-crystal specimens compared with equivalent amounts of impurities in the polycrystalline specimens. Addition of oxygen to polycrystalline tungsten lowered both the ultimate tensile strength and the yield strength, but had no measurable effect on the strength properties of single-crystal specimens. Carbon additions to both polycrystalline and single-crystal specimens did not affect the ultimate tensile strength; however, a large increase in the yield strength resulted. The results suggest that oxygen embrittlement in tungsten is caused by grain-boundary segregation, while carbon embrittlement results from an interaction between carbon atoms and dislocations within the tungsten lattice.