Morphology of adiabatic shear bands in a metastable beta titanium alloy depends on initial microstructure

We investigate the evolution of adiabatic shear bands during dynamic testing in a Ti-10V-2Fe-3Al alloy with three different initial microstructures. For the investigation of the nucleation and propagation of shear bands the deformation of shear-compression samples is limited to predefined nominal axial strains using both strain mapping and subsequent scanning and transmission electron microscopy. In β-titanium with primary α-phase lamellae, massive monolithic bands are formed. In contrast, solution annealed β-titanium and microstructures with primary as well as secondary α lamellae promote the formation of multiple fine, branching shear bands. Additional compression tests under dynamic conditions are used for the evaluation of strain rate sensitivity values. The individual shear band microstructures are in good agreement with the different macroscopic rate sensitivities of the different microstructural conditions. All conditions exhibit ductile fracture patterns after failure and the formation of shear dimples with different sizes that agree with the size of individual microstructural features. Our results highlight that different microstructural features have a significant effect on shear band morphology during dynamic deformation.