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On the evolution of adiabatic shear bands in the beta titanium alloy Ti-10V-2Fe-3Al.

Wednesday (06.11.2019)
14:15 - 14:35
Part of:

Titanium alloys tend to form adiabatic shear bands at high strain rates, mainly because of their low thermal conductivity. Initial strain localization events lead to high local temperatures, resulting in further material softening. The subsequent formation of adiabatic shear bands provides nucleation sites for shear localization and the initiation of failure. The mechanical behavior of β-titanium is also strongly determined by microstructural parameters like β-grain size, morphology and volume fractions of primary and secondary α-phase precipitates – but the effect of different microstructural features on shear band morphologies is not yet well understood. In this study, we investigate the evolution of adiabatic shear bands in a β-titanium alloy (Ti-10V-2Fe-3Al) with two different microstructures: β titanium with primary α phase and β titanium with primary α (identical volume content) + additional secondary α-phase precipitates. Compression-shear tests in different dynamic setups with an initial strain rate up to 10³ 1/s are performed at room temperature. The nominal deformation is limited to predefined compressive strains (2 %, 5 % and 10 %). This approach allows to examine the shear bands at different stages of nucleation and propagation by scanning electron microscopy, and to probe local properties by nanoindentation. While there are only minor differences in the macroscopic mechanical behavior of both microstructural conditions, the formation mechanisms of adiabatic shear bands within the microstructures are different. In the β titanium with primary α-phase, massive bands with a thickness of 5 µm can be observed. In contrast, the β titanium with primary and secondary α-phase exhibits many fine, branching shear bands. Our detailed experimental observations contribute to an in-depth micromechanical understanding of the evolution of adiabatic shear bands in the metastable β-titanium alloy Ti-10V-2Fe-3Al.

Dr.-Ing. Sven Winter
Fraunhofer Institute for Machine Tools and Forming Technology IWU
Additional Authors:
  • Mario Scholze
    TU Chemnitz
  • Prof. Dr. Martin F.-X. Wagner
    TU Chemnitz