Giant thermal expansion and α-precipitation pathways in Ti-alloys.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 29127330.
- Also identified by DOI 10.1038/s41467-017-01578-1 and PMC identifier 5681671.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
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<sup>-6</sup> to -95.1×10<sup>-6</sup> °C<sup>-1</sup>) ever reported. Moreover, we describe two pathways leading to the precipitation of the α-phase mediated by diffusion-based orthorhombic structures, α″<sub>lean</sub> and α″<sub>iso</sub>. 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.