The relationship between accumulation of GN dislocation near the α-β interfaces and the yielding conditions of β phase in dual-phase titanium alloys

Abstract

Crystal plasticity analysis of a single α-β colony in Ti-6Al-4V alloys (Ti-64) was conducted using a geometric model converted from an image obtained by the electron back-scatter diffraction patterns (EBSD), and the relationship between the yielding of β phase and the accumulation of geometrically necessary dislocations (GNDs) was investigated. A dislocation-density-based constitutive equation was employed, and the deformation of the α-β colony was numerically simulated under the condition of uniaxial tensile loading. The results showed that GNDs were accumulated near the α-β interfaces in the conditions that β phase could and could not plastically deform. This is because the spatial gradient of slip strain forms near the α-β interfaces in both conditions. The dependency of vanadium concentration in the β phase (V_β) on the elastic compliance was taken into account in the analysis, and the dependency of V_β on the GND density was also investigated. The GND density was higher with lower V_β on the condition that the β phase did not plastically deform while the relationship could not be observed on the condition that the β phase plastically deformed.