Deformation and Fracture of Strongly Textured Ti Alloy Sheet in Uniaxial Tension

摘要

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-6Al-4V and Ti-5Al-2.5 Sn sheet with either a basal or basal-transverse texture. The results indicate that, by controlling the ease of through-thickness slip, the crystallographic texture strongly affects the plastic of the material but has relatively little effect on the work-hardening rate and strain-rate sensitivity. A strong resistance to through-thickness slip, manifested by a high R-value, enhances the post-uniform elongation and the ability of th 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 critical thickness strain criterion. Calculations of limit strains using an inclined imperfection model are also in good agreement with experimental results. (Author)