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

Slip transfer across the alpha/beta interface was investigated in the near-alpha titanium alloy Ti-5Al-2.5Sn (wt.%). Globular beta-phase grains, located primarily at alpha-phase grain boundaries, enabled the investigation of the orientation relationship between the alpha and beta 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 alpha/beta slip transfer including: Schmid factors, the angle between slip plane normals (psi), the angle between active Burgers' vectors (kappa), and the alpha((0001))/beta({110}) misorientation angle. From an analysis of 36 beta grains, 15 alpha/beta boundaries were found to exhibit the planar alpha((0001))/beta({110)) Burgers' orientation relationship. The alpha 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 beta grain was oriented favorably for slip, i.e. exhibited a high Schmid factor, slip transfer was more likely across the alpha/beta interface compared to when the neighboring 13 phase was not favorably oriented for slip. The alignment between the Burgers' vectors in the a and 13 phases was not well correlated with slip across the alpha/beta interface. Furthermore, the boundaries having the alpha((0001))/beta((110)) orientation relationship were not necessarily favorable for alpha/beta slip transfer. (C) 2012 Elsevier B.V. All rights reserved.