A study of isothermal phase transformation behaviour of TC6 titanium alloy during heat treatment process

Abstract

We report the isothermal phase transformation behavior of TC6 titanium alloy to establish isothermal phase transformation model and constitutive equation in hot working process of TC6 titanium alloy. The phase diagram of the alloy was obtained by thermodynamic calculation, and the effect of temperature on the distribution of each phase was calculated. The phase transition point of TC6 titanium alloy was observed at 985^oC temperature during single stage heat treatment process. The kinetics showed that the amount of α phase decreased gradually and the quantity of β phase increased when the temperature increased. The isothermal transformation kinetics involved the temperature between 750^oC and phase transition temperatures with different holding times. According to kinetics, different double heat treatment processes in two stages were designed and performed also. With the increase of holding temperature of 1^st stage heat treatment, primary α phase was decreased and the decreasing rate accelerated at higher temperature. The characterization of both α and β phase can be effectively controlled by two stages heat treatment process. Thus this research facilitates proper desining of heat treatment process in order to get desired properties of TC 6 Ti alloy for distinct applications.