Kinetics of the ω phase transformation of Ti-7333 titanium alloy during continuous heating

Dilatometry method was used to study the ω phase transformation kinetics of a near-β titanium alloy Ti-7Mo-3Cr-3Nb-3Al during continuous heating. The local activation energy as a function of transformed volume fractionf _ω was determined by Kissinger-Akahira-Sunose (KAS) method, which increases with the transformation proceeding and the average value is about 85.06 kJ/mol. The nucleation and growth mechanism of the ω phase was investigated by the non-isothermal local Avrami exponent n, which appears a significant change with the transformed volume fraction, indicating that the transformation mechanism varies at different stages. The local Avrami exponent lies between 0.5 and 2 in a wide transformed volume fraction range of 0.05-0.9, indicating that the dominating mechanism of ω phase transformation in Ti-7333 titanium alloy is the three-dimensional growth with a near-zero nucleation rate.