Orthorhombic martensite and the ω phase in quenched and deformed titanium alloys with 20–24 at % Nb

X-ray diffraction is used to study phase transformations in quenched and cold-worked titanium alloys with 20–24 at % Nb in a temperature range of 80–373 K and to determine the volume fraction of the orthorhombic martensite and its lattice parameters. As the temperature decreases, the martensite lattice parameter b is found to increase reversibly. This increase leads to a change in the ratio of the orthorhombic lattice parameters, and this change agrees with the tendency of bcc → hcp transition that proceeds as the temperature decreases. In the same temperature range, the fine structure of the retained bcc phase changes reversibly, and these changes are related to the formation of the athermal ω phase during cooling.