Bending springback behavior related to deformation-induced phase transformations in Ti–12Cr and Ti–29Nb–13Ta–4.6Zr alloys for spinal fixation applications

The springback behavior of Ti–12Cr and Ti–29Nb–13Ta–4.6Zr (TNTZ) during deformation by bending was investigated; and the microstructures of the non-deformed and deformed parts of both alloys were systematically examined to clarify the relationship between microstructure and springback behavior. For the deformed Ti–12Cr alloy, deformation-induced ω-phase transformation occurs in both the areas of compression and tension within the deformed part, which increases the Young׳s modulus. With the deformed TNTZ alloy, deformation-induced ω-phase transformation is observed in the area of compression within the deformed part; while a deformation-induced α″ martensite transformation occurs in the area under tension, which is likely to be associated with the pseudoelasticity of TNTZ. Among these two alloys, Ti–12Cr exhibits a smaller springback and a much greater bending strength when compared with TNTZ; making Ti–12Cr the more advantageous for spinal fixation applications.