Stress relaxation induced spheroidization of the lamellar α phase in Ti-7333 alloy

In this paper, stress relaxation tests were performed on β-forged Ti-7333 alloy at the temperature of 750 °C. Transmission Electron Microscope (TEM) and Electron Backscattered Diffraction (EBSD) were adopted to study the microstructure evolution and deformation mechanism. The characterization of microstructure indicates that the residual α lamellae after hot deformation could be broken down during stress relaxation so that a nearly homogeneous globular microstructure can be obtained. The stress exponent and TEM observation show that dislocation creep is the main deformation mechanism, leading to the formation of high angle boundaries across the α plates and the breaking up of α lamellae. Dynamic recovery is the main mechanism in the β phase during stress relaxation.