Deformation mechanisms of a commercial titanium alloy Ti6Al4V as a function of strain rate and initial texture

This paper presents the results of an experimental study on the mechanical behaviour of a commercial titanium alloy Ti6Al4V. One of the aims was to characterize the influence of adiabatic shear banding during compression at room temperature and at different strain rates. Cylindrical specimens were fabricated from an extruded bar in the mill annealed condition. For the lower strain rates, these specimens were deformed in uni-axial compression at room temperature by means of a servo-hydraulical testing machine. A Split Hopkinson Pressure Bar was used for the higher strain rate domain. The compression axis was taken both parallel and perpendicular to the extrusion axis of the as received bar, in order to take into account the contribution of the initial crystallographic texture. The microstructural evolution was carried out using optical and electron scanning microscopy, more particularly for determining the onset of adiabatic shear banding. One of the major observations is that adiabatic shear banding is starting at much lower strain rates as could be found in the current literature, and this as a function of the compression axis orientation. These results have an important influence on the ballistic behaviour.