Investigations of α + β → β Phase Transformation in Monotonically Heated Ti6Al7Nb Alloy / Badania Przemiany Fazowej α + β → β W Stopie Ti6Al7Nb Przy Nagrzewaniu Ciągłym

This paper presents an evaluation of critical temperatures of α + β → β phase transformation in an Ti6Al7Nb alloy occurring during heating performed by dilatometric and metallographic methods. Also, changes in the alloy microstructure during cooling down from the two-phase ( α + β ) and single phase ( β ) ranges have been analysed. In the microstructure of the alloy quenched from temperature above 1010°C (one-phase range) in water, the very fine, needle-like precipitates (presumably α ’) were observed as well as abnormal grain growth of the primary β phase. The obtained results may serve for the interpretation of phase transformation occurring in the Ti6Al7Nb alloy during tempering. In future, the kinetics of the phase transformation during tempering will be investigated by original CHT (Continuous-Heating-Transformation) charts, which are commonly applied for iron-base alloys.