Revisiting the lamellar globularization behavior of a two-phase titanium alloy from the perspective of deformation modes

摘要

The correlation between lamellar globularization and deformation modes during the primary hot processing of titanium alloy was evaluated by means of uniaxial compression, tension, torsion and plane strain compression tests. The microstructure evolution features and underlying globularization mechanisms were comparatively studied via Electron Backscattered Diffraction technique. Noticeable divergences of globularization response are captured in different deformation modes, especially for the globularized fractions and the critical strain. In the face of the strain applied is less than the critical globularization value (0.4-0.63) under uniaxial compression, the lamellae can be still globularized under tension or torsion deformation. But the growth rate of globularized fraction is more sluggish under tension than that under torsion deformation. The lamellae separation at early tension deformation preferentially occurs at junctions of lamellae without destroying Burgers Orientation relationship and significant orientation fluctuation. Shear deformation can facilitate the formation of intra-alpha boundaries and its distribution uniformity, which could make the lamellae grow up into globularized particles and improve the globularization heterogeneity. It is envisaged that the results obtained can provide guidance for the technology scheme and route design of primary hot working of titanium alloy aiming at the homogeneous equiaxed grains.