Torsion Induced Recrystallization of Molybdenum and Tungsten Filaments

Abstract

When an optimum amount of permanent twist is introduced in 3‐ to 10‐mil filaments of molybdenum or tungsten, single crystals up to 15 cm in length grow by either the moving gradient or Robinson techniques. About 5 turns per inch for W at 2500°K or for Mo at 1650°K was favorable. Although there is evidence of perfection in the volume of the crystals, the twist leaves a threadlike surface imperfection which remains even after severe heat treatment at evaporation temperatures.