Author: Walter R. Witzke

Publisher:

Published: 1966

Total Pages: 28

ISBN-13:

Ingot structures resulting from electron-beam melting of tungsten consist mainly of columnar grains extending the length of the ingot. In order to examine the grain refining capabilities of various elemental and refractory compound additions, small ingots of tungsten containing these additions were prepared by electron-beam melting. Measurements on transverse ingot sections from each melt indicated that all the additions decreased the average grain diameter of the columnar grains typical of electron-beam melted tungsten and that grain refining effectiveness varied with the concentration of the solute S. Losses of the additions during melting were in excess of 90 percent in many cases. The most potent grain refiner was boron. A nominal addition of 0. 5 weight percent decreased the average grain diameter of the columnar grains from 0. 48 to 0. 008 centimeter. The effectiveness of the elemental additions decreased in the following order: boron, yttrium, carbon, hafnium, zirconium, molybdenum, columbium, rhenium, and tantalum. The losses of these elements during melting also decreased in approximately the same order. The elemental additions were generally more effective grain refiners than the refractory compounds. The elements with the smallest distribution coefficients were the most effective grain refiners.