The mechanical properties of some ductile niobium and tantalum base alloys prepared by electron beam melting

Abstract

This paper presents the results of studies made on a relatively small number of niobium and tantalum base alloys. Using impact transition temperature as a criterion for initial evaluation, a number of alloys have been selected for high temperature tensile and creep rupture tests as well as fabrication studies. These data are being obtained at the present time, and more complex modifications of these alloys are being explored. Tantalum alloys containing more than 20% tungsten are very brittle and this limits the usefulness of the combination. Present investigations in our laboratory, as well as at others, are directed toward the development of more complex alloys to take advantage of the exceptional ductility exhibited by tantalum base alloy systems. Niobium alloy development is still in its infancy. Although the electron beam process restricts the number of combinations of alloying elements that can be used, there is a good possibility that, in addition to tungsten, molybdenum, and zirconium, rhenium and hafnium may materially improve high temperature properties. Economic reasons, however, restrict the amounts of these latter two additions that can be used at present. Although at other laboratories there are higher strength niobium alloys being prepared than the ones discussed here, they are considerably less fabricable and ductile. The efforts of this investigation have been directed toward the development of alloys with good fabricability rather than stronger alloys with severe fabrication problems.