Giant thermal expansion and ?-precipitation pathways in Ti-alloys.

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^-6 to -95.1×10^-6?°C^-1) ever reported. Moreover, we describe two pathways leading to the precipitation of the ?-phase mediated by diffusion-based orthorhombic structures, ??_lean and ??_iso. Via coupling the lattice parameters to composition both phases evolve into ? through rejection of Nb. These findings have the potential to promote new microstructural design approaches for Ti-Nb alloys and ?-stabilized Ti-alloys in general.

SUBMITTER: Bonisch M 

PROVIDER: S-EPMC5681671 | biostudies-literature | 2017 Nov

REPOSITORIES: biostudies-literature