Total Recovery Strain Research Articles

Anisotropy and Temperature Dependence of Young’s Modulus in Textured TiNbAl Biomedical Shape Memory Alloy

Anisotropy and temperature dependence upon the Young’s Modulus of Ti–24 mol %Nb–3 mol %Al (TiNbAl), a new biomedical shape memory alloy, were characterized in the temperature range from 133 to 413 K by dynamic mechanical analysis in the tensile mode. The material consisted of � -phase (the parent phase, bcc) at room temperature and a well developed f112gh110i type recrystallization texture was formed by a severe cold-rolling followed by a recrystallization heat-treatment. Test specimens were prepared from the textured material with the longitudinal direction of specimens being systematically varied within the ND-plane. Young’s modulus was measured as a function of temperature along each loading direction. A large depression in Young’s modulus was observed around � -� 00 martensitic transformation temperature, below room temperature. The Young’s moduli of the textured material exhibited anisotropy depending on the loading direction. Compliance anisotropy factor, J, and characteristic modulus S11 of the � -phase were calculated from the obtained results based upon the assumption that the texture was perfectly developed in the material. It was found that the Young’s modulus of the � -phase reaches a minimum value along h001i and a maximum value along h111i in the measured temperature range. A suitable texture to increase the total recovery strain in superelasticity and anisotropy of Young’s modulus were discussed based on the obtained results.