Giant thermal expansion and α-precipitation pathways in Ti-Alloys


Ti-Alloys represent the principal structural materials in both aerospace development and metallic biomaterials. Key to optimizing their mechanical and functional behaviour is in-depth know-how of their phases and the complex interplay of diffusive vs. displacive phase transformations to permit the tailoring of intricate microstructures across a wide spectrum of configurations. Here, we report on structural changes and phase transformations of Ti-Nb alloys during heating by in situ synchrotron diffraction. These materials exhibit anisotropic thermal expansion yielding some of the largest linear expansion coefficients (+ 163.9×10-6 to-95.1×10-6 °C-1) ever reported. Moreover, we describe two pathways leading to the precipitation of the α-phase mediated by diffusion-based orthorhombic structures, α″lean and α″iso. Via coupling the lattice parameters to composition both phases evolve into α through rejection of Nb. These findings have the potential to promote new microstructural design approaches for Ti-Nb alloys and β-stabilized Ti-Alloys in general.

niobium, titanium, alloy, complexity, crystal structure, diffusion, lattice dynamics, optimization, parameterization, precipitation (chemistry), thermal expansion, titanium, transformation, anisotropy, Article, crystal structure, diffraction, diffusion, functional behavior, heating, precipitation, X ray diffraction
Bönisch, M., Panigrahi, A., Stoica, M., Calin, M., Ahrens, E., Zehetbauer, M., et al. (2017). Giant thermal expansion and α-precipitation pathways in Ti-Alloys. 8(1).
CC BY 4.0 Unported