Mechanical Working of Refractory Alloys Produced by Melting Processes

Abstract

AbstractThe elements generally considered to be the “major” refractory metals are niobium (Nb) and tantalum (Ta) from group VA of the periodic table, and molybdenum (Mo) and tungsten (W) from group VIA. By virtue of their high melting points, these metals and their alloys constitute an important class of materials. When they are produced by melting processes, the resulting ingots usually have large grain sizes, which need to be refined during mechanical working. While the unalloyed refractory metals have varied room-or-low-temperature applications, they require alloy additions, in many cases substantial, to meet the requirements of most of their hightemperature applications. This often results in high flow stresses at elevated working temperatures, and a concomitant decrease in low-temperature ductility. As BCC materials, the refractory metals have ductile-to-brittle transition temperatures, which vary widely from one metal to another and with other metallurgical variables. All of these factors must be taken into account in order to develop successful processing schedules for the refractory metals.