Stress-induced omega phase transformation in Ti--V alloys

The deformation behavior of bcc (β) Ti--V single crystals containing the athermal ω phase was studied using tensile tests, optical and electron microscopy, and x-ray and electron diffraction. The stress-strain curves were characterized by a marked yield point and an essentially zero work hardening rate. The deformation structures consisted of wavy slip and stress-induced plates. Both x-ray and electron diffraction showed that the stress-induced plates consist of one variant of the omega phase, with the orientation relation to the parent β phase close to (0001)/sub ω/ parallel (001)/sub β/; (11 anti 2 0)/sub ω/ parallel (110)/sub β/. The habit plane was of the type [554]. A small amount of α'(hcp) phase was present within the ω plate, with orientation relation to the β phase close to the Burgers relationship i.e. (0001)/sub α'/ parallel (110)/sub β/; [11 anti 2 0]/sub α'/ parallel [anti 1 11]/sub β/. It is suggested that the ω phase may be an intermediate structure in the stress-induced bcc → hcp transformation. (auth)