Interface characteristics in an α+β titanium alloy

Ackerman, Abigail K. and Vorontsov, Vassili A. and Bantounas, Ioannis and Zheng, Yufeng and Chang, Yanhong and McAuliffe, Thomas and Clark, William A. and Fraser, Hamish L. and Gault, Baptiste and Rugg, David and Dye, David (2020) Interface characteristics in an α+β titanium alloy. Physical Review Materials, 4 (1). 013602. ISSN 2475-9953 (https://doi.org/10.1103/PhysRevMaterials.4.013602)

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Abstract

The α/β interface in Ti-6Al-2Sn-4Zr-6Mo (Ti-6246) was investigated via center of symmetry analysis, both as-grown and after 10% cold work. Semicoherent interface steps are observed at a spacing of 4.5±1.13 atoms in the as-grown condition, in good agreement with theory. Lattice accommodation is observed, with elongation along [1210]α and contraction along [1010]α. Deformed α exhibited larger, less coherent steps with slip bands lying in {110}β. This indicates dislocation pile-up at the grain boundary, a precursor to globularization during heat treatment. Atom probe tomography measurements of secondary α plates in the fully heat-treated condition showed a Zr excess at the interface, which was localized into regular structures indicative of Zr association with interface defects, such as dislocations. Such chemo-mechanical stabilization of the interface defects would both inhibit plate growth during elevated temperature service and the interaction of interface defects with gliding dislocations during deformation.

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