Typical Microstructural Characteristics of Ti–5Al–5Mo–5V–3Cr–1Fe Metastable β Ti Alloy Forged in α + β Region

Abstract

In this study, typical microstructural characteristics of a metastable β Ti alloy (Ti–5Al–5Mo–5V–3Cr–1Fe) forged in a dual-phase region (strain of 54% at 820 °C) were investigated in detail by the combined use of X-ray diffraction, energy dispersive spectroscopy, electron channeling contrast imaging and electron backscatter diffraction techniques. Results show that the microstructure of the forged alloy is composed of bulk α grains, α plates and β matrix. The bulk α grains correspond to retained primary α phase (αp, average grain size ~ 2.4 μm), while the α plates are secondary α phase (αs, width ~ 70 nm) precipitated from the β matrix during air cooling. During forging, the β matrix experiences dynamic recovery with many subgrains and significant orientation gradients formed. Analyses of the orientation relationship between the α and β phases show that the Burgers orientation relationship is not maintained between some αp and β phases, which should be related to thermal deformation-induced changes of their orientations. In contrast, all of the αs plates are found to maintain well the Burgers orientation relationship with the β phase.