Deformation and fracture of strongly textured Ti alloy sheets in uniaxial tension

The influence of crystallographic texture on the deformation and fracture behavior of strongly textured Ti alloy sheet has been investigated. Uniaxial tensile tests have been performed on Ti-6A1-4V and Ti-5A1-2.5 Sn sheet with both a basal and a basal-transverse texture. The results indicate that, by controlling the ease of through-thickness slip, the crystallographic texture strongly affects the plastic anisotropy of the material but has relatively little effect on the strain-rate sensitivity and work-hardening rates at large strains. A strong resistance to through-thickness slip, manifested by a high R-value, enhances the post-uniform elongation and the ability of the material to retain the load-carrying capacity beyond maximum load. This behavior can be qualitatively understood in terms of the effect of R on the hardening which occurs as the strain state within the diffuse neck shifts from uniaxial tension toward plane strain. A higher R-value also increases significantly the limit strain at the onset of localized necking as well as the fracture strain. The effects of R-value on the limit strain can be qualitatively understood in terms of a critical thickness strain criterion and can be quantitatively predicted by two analyses, one of which assumes an imperfection to be present while the other does not. © 1983 The Metallurgical of Society of AIME