Analysis of slip transfer and deformation behavior across the α/β interface in Ti–5Al–2.5Sn (wt.%) with an equiaxed microstructure

Abstract

Slip transfer across the α/β interface was investigated in the near-α titanium alloy Ti–5Al–2.5Sn (wt.%). Globular β-phase grains, located primarily at α-phase grain boundaries, enabled the investigation of the orientation relationship between the α and β phases in the case of a general equiaxed microstructure. Active deformation systems were identified using electron backscattered diffraction (EBSD) supported by plane trace analysis. Information from the plane trace analysis was used to assess a number of metrics that could correlate with α/β slip transfer including: Schmid factors, the angle between slip plane normals (ψ), the angle between active Burgers’ vectors (κ), and the α(0001)/β{110} misorientation angle. From an analysis of 36 β grains, 15 α/β boundaries were found to exhibit the planar α(0001)/β{110} Burgers’ orientation relationship. The α phase, which dominated the microstructure, tended to exhibit slip traces for high global Schmid factor slip systems, including prism, basal, and pyramidal slip planes. When the neighboring β grain was oriented favorably for slip, i.e. exhibited a high Schmid factor, slip transfer was more likely across the α/β interface compared to when the neighboring β phase was not favorably oriented for slip. The alignment between the Burgers’ vectors in the α and β phases was not well correlated with slip across the α/β interface. Furthermore, the boundaries having the α(0001)/β{110} orientation relationship were not necessarily favorable for α/β slip transfer.