Stretch forming and fracture of strongly textured Ti alloy sheets

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Department of Materials Science and Engineering


The influence of plastic anisotropy and R -value on the stretch forming and fracture behavior of strongly textured Ti-6A1-4V and Ti-5Al-2.5Sn sheets has been examined utilizing sheet specimens with a wide range of R -values but with similar work hardening and strain-rate sensitivity characteristics. The results indicate that a high R -value and difficult through-thickness slip enhance the forming limit as well as fracture strains when the minor strain in the plane of the sheet is negative, this effect being most pronounced at uniaxial tension. At plane strain, the R -value has little or no influence on the limit or fracture strain. A direct determination of the effect of R -value on the biaxial stretch forming characteristics of Ti-6-4 sheet is precluded by the intervention of fracture prior to localized necking when the minor strain is positive. The influence of plastic anisotropy on both the localized necking and the fracture behavior can be generally understood in terms of the difficulty of attaining critical thickness strains as through-thickness slip becomes more difficult.

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Metallurgical Transactions A