Failure mechanism and mode of Ti-6Al-4V alloy under uniaxial tensile loading: Experiments and micromechanical modeling

The failure of dual-phase alloys under tensile loading conditions is often due to the nucleation, growth and coalescence of voids at the interface between different phases from micromechanical point of view. The aim of this paper is to identify the failure mechanism and mode of dual-phase Ti-6Al-4V alloy in the form of plastic strain localization due to the incompatible deformation between the softer α phase and the harder β phase under the uniaxial tensile loading condition. The failure modes of as-received and heat-treated alloy are determined by tensile tests using sheet specimens. Then, a micromechanical modeling approach is developed on the basis of actual microstructure to predict the failure modes and ultimate ductility. Two different failure modes, i.e., shear band and vertical split band, can be found for as-received material. However, only vertical split failure is observed for heat-treated alloy. The predicted results agree well with the experimental observations. The microstructure-level inhomogeneity and incompatible deformation between the hard and soft phases are the main reason for failure.