Correlation between dislocation-density-based strain hardening and microstructural evolution in dual phase TC6 titanium alloy

Owing to their complex microstructures, the strain hardening of titanium alloys remains poorly understood. Therefore, the plastic deformation processes of the α and β phases in dual-phase TC6 (Ti-6Al-2.5Mo-1.5Cr-0.5Fe-0.3Si) titanium alloy were investigated via high-energy X-ray diffraction with in situ tensile loading. Dislocation density evolution in both the α and β phases was quantified via X-ray diffraction line profile analysis complemented by transmission electron microscopy measurements. The strain hardening rate calculated based on this evolution matched the strain hardening behaviors shown in the stress-strain curves. Furthermore, the effect of interactions between subgrain boundaries and slip systems were elucidated through transmission electron microscopy (TEM) observations. The evolution of strain hardening rate, as well as the dislocation density, was correlated with and well explained by the typical microstructures formed in different deformation regimes.