In situ characterization of a high work hardening Ti-6Al-4V prepared by electron beam melting

A multi-phase Ti–6Al–4V prepared by electron beam melting and thermal post treatments has been shown to exhibit increased strength and ductility over standard wrought or hot isostatic pressed Ti–6Al–4V. The mechanical improvements are due to a prolonged, continuous work hardening effect not commonly observed in Ti alloys. In situ x-ray diffraction and high resolution digital image correlation are used to examine the strain partitioning between the phases during tensile loading with post-mortem electron microscopy to characterize the deformation behavior in each phase. Specimens heat treated between 850 and 980 °C were tested and the effect of annealing temperature on the micromechanical response is discussed. It is shown that the work hardening is the result of composite load-sharing behavior between three mechanically distinct microstructures: large α lamellae and a martensitic region of fine acicular α' and a third phase not previously reported in this alloy.