Unusual dynamic precipitation softening induced by dislocation glide in biomedical beta-titanium alloys.

ABSTRACT: Softening of metallic materials containing precipitates during cyclic deformation occurs through dissolution of the precipitates, because the to-and-fro motion of the dislocation causes dissolution of the precipitate particles by cutting them. Here, however, we found the completely opposite phenomenon for the first time; a "dynamic precipitation softening" phenomenon. In a Ti-35Nb-10Ta-5Zr body-centered cubic structured ?-Ti alloy single crystal developed for biomedical implant, the to-and-fro motion of the dislocation "induced" the selective precipitation of the ?-phase whose c-axis is parallel to the Burgers vector of the moving dislocation, which led to the significant cyclic softening of the crystal. The formation of the ?-phase is generally believed to induce significant hardening of ?-Ti alloys. However, the present results suggest that this is not always true, and control of the anisotropic features of the ?-phase via control of crystal orientation can induce unusual mechanical properties in ?-Ti alloys. The unique anisotropic mechanical properties obtained by the cyclic-deformation-induced oriented ?-phase formation could be useful for the development of "single-crystalline ?-Ti implant materials" with advanced mechanical performance.

SUBMITTER: Hagihara K 

PROVIDER: S-EPMC5556124 | biostudies-literature | 2017 Aug

REPOSITORIES: biostudies-literature