Effect of tantalum addition on the tensile properties of V-Ta-4Cr-4Ti quaternary alloys

Various V-Ta-4Cr-4Ti quaternary alloys containing different amounts of Ta were investigated to determine the effect of Ta concentration on their tensile properties. Six button-shaped ingots of V-xTa-4Cr-4Ti alloys (x = 4, 8, 15, 22, 24, and 35 wt.%) were fabricated on a laboratory scale by using non-consumable arc-melting in argon atmosphere. The sheet specimens for all the V-Ta-4Cr-4Ti alloys examined herein were obtained by cold-rolling; hot-rolling or intermediate annealing was not required. Although the examined alloys were fabricated on a laboratory scale, the high-Ta alloys, unlike the high-Cr alloys, did not experience crack formation in the cold rolling process. It is possible that V-4Cr-4Ti alloys adopt large amount of Ta and its strengthening effect without negative impact on rolling fabricability. Tensile strength tended to increase with increasing Ta content at both room temperature and high temperatures of 973 K and 1073 K, which can be attributed to the solid solution strengthening by Ta. Thus, addition of Ta to V-4Cr-4Ti alloys can improve their strength without decreasing their rolling fabricabilities. However, an alloy containing excess Ta (V-35Ta-4Cr-4Ti) showed a loss of ductility and a brittle fracture mode due to the formation of a large amount of friable Laves phase. Therefore, it is necessary to limit the amount of Ta to prevent the formation of the Laves phase.