Deformation behaviour of Ti-8Ta-3Nb during hot forging

Ti-8Ta-3Nb, as a new biomaterial, was prepared by cast and swaging process. Their deformation behavior of Ti-8Ta-3Nb alloy has been characterized on the basis of its flow stress variation obtained from the true strain rate compression testing in the temperature of 700-900 degrees C and strain rate of 0.001-10 s(-1). At the strain rates lower than 0.1 s(-1) and the all temperature ranges which consist of two phase alpha+beta as well as beta single phase Fields, the flow curves show a small degree of now softening behavior. In contrast, the shapes of the now Curves at other strain rates indicate unstable behavior. The shapes of the flow curves were similar in both as-cast and swaged specimen Lis well as in both alpha+beta phase and beta phase. The flow stress data did not obey the kinetic rate equation over the entire regime of testing but a good fit has been obtained in the intermediate range of temperatures (750-850 degrees C). In this range, a stress exponent value of about 7.7 in as-cast specimens and about 6.2 in swaged specimens with an apparent activation energy of about 300 kJ/mol and about 206 kJ/mol respectively have been evaluated.