The effect of transformed β-phase on local area plastic deformation and dislocation characteristics of Ti6242s alloy under low-cycle fatigue and dwell fatigue

For the aims of this study, the local area plastic deformation and dislocation characteristics of the Ti–6Al–2Sn–4Zr–2Mo-0.1Si alloy under low-cycle fatigue and dwell fatigue at room temperature were closely analyzed. The main outcomes of intragranular-local-misorientation of the samples after different low-cycle fatigue and dwell fatigue cycles showed that inhomogeneous plastic deformation occurred in local areas in the equiaxed primary α-phase and the transformed β-phase. High plastic deformation areas preferably existed in transformed β-colonies and some equiaxed primary α-grains, whereas low plastic deformation areas tended to exist only in equiaxed primary α-grains. Different from the related descriptions in traditional crystal plastic finite element simulation, the definite relationship between the crystallographic orientation of low plastic deformation equiaxed primary α-grains and the fatigue loading direction was not found. Furthermore, transmission electron microscopy dislocation analysis showed that banded dislocations formed in some equiaxed primary α-grains under the effect of the nearby transformed β-phase. Such bands were related to the arrangement direction of α+β colonies in the transformed β-phase and the crystallographic orientation of the primary α-phase. This deformation coordination behavior between the equiaxed primary α-phase and the transformed β-phase analyzed and aforementioned in the titanium alloys with a relatively low volume fraction of the primary α-phase requires further examination.