Nowadays, α/β layered microstructure is attracting attention as one of the methods which improve mechanical properties in Ti alloys. In our previous studies, it has been revealed that compositional modulated αZr-rich/αZr-lean layered microstructure is formed in the slow-cooled Ti–35Zr (at.%) binary alloy. So, we focused on the possibility of forming α/β layered microstructure with compositional modulation by adding β-stabilizer. In this study, we chose V and Fe which have different β phase stabilization effects. (Ti–35Zr)–xV and (Ti–35Zr)–yFe alloys (x, y = 0.5 – 5 at.%) fabricated by vacuum arc melting were annealed at 1000°C (β phase field) for 2 h and subsequently slow-cooled to room temperature at 50°C/h. Scanning electron microscope observation revealed that the layered microstructure were formed at x = 0.5 – 1 and y = 0.5 – 4. To investigate crystalline phases and orientation relationship in layered microstructure, electron backscatter diffraction measurement and energy dispersive X-ray spectroscopy analysis were conducted. These measurements showed that the enrichment of V and Fe resulted in the retention of β phase in the Zr-rich layer, leading to the formation of an α/β layered microstructure with compositional and structural modulation. In addition, it was found that the state of microstructure (αZr-rich/αZr-lean layered microstructure, α/β layered microstructure, and non-layered α/β) can be organized by using Moeq value. The Vickers hardness increases with increasing concentration of β stabilizer, but its value does not differ between layered and non-layered microstructures. These results indicates that the addition of V and Fe is an effective approach to introduce α/β layered microstructure into Ti–Zr alloys.
Morizono et al. (Thu,) studied this question.