THE FLOW AND FRACTURE OF ZONE REFINED TUNGSTEN.
FRANKLIN INST PHILADELPHIA PA LABS FOR RESEARCH AND DEVELOPMENT
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This report covers the first efforts toward purification of tungsten by induction floating zone melting. The difficulties encountered in initial melting efforts were poor visibility and inadequate zone length control. The former was overcome by using a preliminary solid state vacuum outgassing treatment. The latter difficulty was partly solved with the use of a levitation type melting coil to support the molten zone. Tensile specimens were prepared by spark and chemical machining techniques. Specimens were tested with three electron beam zone passes, one induction zone pass, and three electron beam followed by four induction zone passes. The critical resolved shear stresses decreased in the order listed above, with the one induction zone pass material showing lower CRSS than the three electron beam zone pass material. The tensile results are considered encouraging, but the relatively poor induction zone melting conditions attained prevented a full evaluation of this process. Author