ISSN:
1573-4803
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract The structures of chemical vapour deposited (CVD) tungsten and a tungsten-22 wt % rhenium alloy in the as-deposited condition, were studied by scanning and transmission electron microscopy. Deposition occurs by the advancement of ledges up the {111} surfaces of four-sided pyramids. Grain growth was studied in the alloy at thirteen temperatures between 1400 and 2780°C. For annealing times of less than 1 h the apparent activation energy was 62±2 kcal mol−1. After several hours at temperatures above 2270°C the rate of grain growth decreased because of the development of bubbles at grain boundaries. Lamellar composition fluctuations were noted metallographically and by electron probe microanalysis. For CVD tungsten, the widening of columnar grains was studied at ten temperatures between 1290 and 2555°C. The rate of increase of columnar grain width became significant only at temperatures above 1980°C.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00550460
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