Ascertaining the deformation accommodation of a novel Ti-652 alloy by tracking the evolution of slip traces and lattice strain

The exploration of slip modes in metallic materials during deformation has been long suffered from either insufficient statistical accuracy of slip trace analysis or limited spatial resolution by X-ray diffraction. In this work, a combination of slip trace analysis based on in-situ Electron Backscatter Diffraction (EBSD) and lattice strain analysis supported by in-situ Synchrotron Radiation High-Energy X-ray Diffraction (SR-HEXRD) was employed to determine the deformation accommodation mechanisms of a new developed Ti-6Al-5Mo-2Sn-0.3Si-0.5 V (Ti-652) alloy. Different from conventional cases, it was surprisingly found that pyramidal (101̅1)_α slip is easier to be initiated than prismatic (101̅0)_α within α grains, resulting in the dominant slip modes evolving from prismatic <a> to pyramidal I <c+a>. In addition, in-situ EBSD results show that slip can transfer across grain boundary (GB) in counterintuitive situations with low geometric compatibility factor m^′ of 0.5, or with GB misorientations in the range of θ≥24.5°, which are contractive to the slip transfer criterion in hcp structures. Further detailed crystallographic analysis revealed that specific slip transferred across GBs with 24.5°≤θ≤60° because of high Schmid Factor (SF) values, while with θ>60° slip transfer occurred by activating another slip systems. The accumulation of multi-mode slip dislocations induced by deformation accommodation with different phases was suggested to promote the formation of sub-GBs within the deformed parent grain. These findings provide insights of the slip behaviors and property tailoring in Ti alloys.