High temperature deformation and microstructural evolution of core-shell structured titanium alloy

The hot deformation behavior and microstructural evolution of a core-shell (soft coarse-grained Ti cores and hard Ti-N solid solution shells) structured titanium alloy were investigated under 800–950 °C at a strain rate range of 0.001–1 s−1. The core-shell structured titanium alloys exhibit a higher flow stress (195 MPa deformed at 800 °C/0.1 s−1) compared with that of pure Ti (48 MPa deformed at 800 °C/0.1 s−1), suggesting that core-shell structure promotes a strengthening effect of titanium alloys. The nitrogen solution strengthened hard shells squash along compression direction playing a roll of skeleton and the soft cores accommodate the deformation, leading to inhomogeneous deformation. Dynamic recrystallization takes place mainly adjacent to the shells due to stress and strain concentration. The improvement compression stress of core-shell structured titanium alloys is attributed to the nitrogen-induced solution strengthening and core-shell structure itself, together with the inhabited plastic deformation and dynamic recrystallization by core-shell structure.