Microstructural Evolution Behaviors and Deformation Mechanisms in Ti-5Mo-xFe (x=1, 2wt%) Alloy

Cast β titanium alloys exhibit low mechanical properties and are therefore suitable for various thermomechanical processing methods, such as forging, hot rolling, and extrusion, before practical applications. Depending on β stability, different deformation mechanisms, including slip, stress-induced martensite (SIM), and twinning, can occur, leading to diverse mechanical properties. Thus, controlling β stability and thermomechanical processing conditions are crucial to tailoring the properties of β titanium alloys. In this study, Ti-5Mo-xFe (x = 1, 2 wt%) alloys were investigated. The β stability was adjusted by varying the Fe content, and hot rolling was performed at 900°C with a 60% reduction in thickness. In the Ti-5Mo-1Fe alloy, due to its relatively low β stability, dynamic strain-induced transformation of the α phase predominantly occurred, accompanied by deformation mechanisms involving slip as well as tensile twins with an 86° misorientation and compressive twins with a 64° misorientation. Conversely, in the Ti-5Mo-2Fe alloy, which exhibited higher β stability, dynamic recrystallization of the β phase was the dominant deformation mechanism, and {332}<112> twins along with α'' martensite formed by stress-induced martensitic transformation adjacent to the twin boundaries were observed. These findings demonstrate that precise control over β stability through compositional tuning effectively tailors the deformation mechanisms, thereby significantly influencing the microstructural evolution and mechanical properties of β titanium alloys.