Effects of volume fraction and morphology of transformed beta phase on the mechanical properties of titanium - 6-aluminum - 4-vanadium alloy

The effects of the volume fraction and morphology of transformed beta phase on the mechanical properties of Ti-6Al-4V were analyzed. An aging experiment was performed in order to study the decomposition of the unstable martensite and its effects on the mechanical properties. Scanning electron microscope (SEM) observations of tensile specimen fractured surfaces were made to determine the fracture mechanisms. It was observed that neither the transformed beta volume fraction nor its morphology have a significant effect on the strength of this alloy. However, the ductility, ranging from 1.7% to 17%, was strongly influenced by the amount and morphology of the transformed beta. The high dislocation density in the water quenched martensite resulted in the lowest ductility, while the air cooled basketweave structure acted as a barrier to crack propagation resulting in higher ductility values. The precipitated beta particles during aging at 550...