The effects of tungsten addition on the microtexture and mechanical behavior of tantalum plate

Abstract

Microtexture variations in annealed tantalum and tantalum–tungsten alloy plate materials have been studied by orientation imaging microscopy (OIM) and correlated with the mechanical behavior over a strain rate range of 10 −3 s −1 to 3000 s −1. Plates of nominally pure Ta and Ta–W alloys (2.5, 5 and 10 wt% W), ≈6 mm thick were mechanically tested quasistatically in compression and tension and dynamically via a split Hopkinson pressure bar and punch through shear tests. The results indicate that the unalloyed Ta exhibits anomalous mechanical responses such as inverse barreling or hourglassing in compression and multiple necks in tension, whereas the tungsten containing alloys deform homogeneously. OIM indicates severe texture banding in the pure Ta such that the fraction of grains with near 〈111〉 normals is very high near the centerline of the plate and decreases toward the surfaces. Large deviations from this generic description occur from specimen to specimen. Microtexture analyses of the Ta–W alloys reveals no significant texture gradients but rather a change in overall texture from a 〈111〉 fiber to a 〈100〉 cube texture with the addition of 2.5 wt% tungsten. The evidence suggests that the addition of tungsten results in a more uniform texture and thus homogeneous mechanical response.