Anisotropy and temperature dependence of young's modulus in textured TiNbAl biomedical shape memory alloy

Abstract

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 β-phase (the parent phase, bcc) at room temperature and a well developed {112} 〈110〉 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 β-α″ 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 β-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 β-phase reaches a minimum value along 〈001〉 and a maximum value along 〈111〉 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. © 2005 The Japan Institute of Metals.